• Clinical Abstracts

    Clinical Abstracts on Esophageal Electrocardiography

    Esophageal Lead Ambulatory Monitoring with QRST Subtraction Demonstrates Left Atrial Initiation of Paroxysmal Atrial Fibrillation. Guerra P, Sparks P, Mlynash M, Groenewegen AS, Roithinger F, Steiner P, Lesh MD. Univ of California San Francisco. Abstract presented at North American Society of Pacing and Electrophysiology, Toronto. May, 1999. Background:  Recent results suggest a pulmonary vein (PV) focus triggers AF in patients with paroxysmal atrial fibrillation (PAF). Given the difficulty in inducing triggering beats in the EP laboratory, a noninvasive screening tool for left atrial (LA) triggers is desirable. Methods: We evaluated the utility of ambulatory esophageal lead monitoring (ELAM) to identify patients with LA premature beats (APBs) which initiate AF. Because of its proximity to the posterior left atrium (LA), early activation in the esophageal lead should occur at or before the onset of the surface P wave for the APBs arising from the PV region. Recognition of initiating APBs on the EKG is hampered by the superimposed T waves. A novel automatic QRST subtraction algorithm was applied to the Holter data to isolate ectopic P waves. ELAM was performed on 17 patients referred to PAF using a Mortara Instruments 12-lead recorder. A 10 French bipolar esophageal lead (CardioCommand TAPSCOPE-210) was positioned such that an adequate atrial signal was obtained. Results: ELAM was performed for a mean of 16.5 +/- 6.3 hours and the esophageal lead was well tolerated in all. Ten patients had a total of 40 PAF initiations. During sinus rhythm, the atrial signal recorded from the esophageal lead occurred 33 +/- 6 msec after the surface P wave, reflecting the expected late LA activation. All PAF episodes were initiated by an APB. Atrial activation during APB was consistently early in all the esophageal tracings, occurring a mean of 28 +/- 11 msec before the onset of the P wave revealed by QRST-subtraction of the surface tracings. These patients underwent invasive mapping of the initiating foci for PAF. Two patients had left upper PV foci, 2 hard right upper PV foci, 1 a left lower PV focus, 1 a right lower PV focus, and 2 patients had foci in both upper PVs. Two patients did not have sufficient APBs to permit mapping. Conclusions: 1) Ambulatory esophageal EKG monitoring is feasible and when compared to QRST subtraction can reveal left atrial foci as initiators of PAF. 2) Documenation of early esophageal lead activation for APBs that initiate AF is highly predictive of PV triggers, and may serve as a useful screening test for candidates for focal AF ablation.

    A noninvasive transesophageal signal averaging technique for detection of sinus node electrogram. Ding S, Ma D, Guo C. Division of Cardiovascular Diseases, Wuhan General Hospital, Wuhan, Hubei, P.R. China. Dinfsfmd@Yahoo.com. J Interv Card Electrophysiol 4(1):225-30, 2000. We have developed a noninvasive transesophageal signal averaging technique for direct recording of sinus node electrogram. In this study, sinus node electrograms were recorded from 106 of 138 patients (77%), comparable to that (46%) recorded by conventional transesophageal technique, 59 were male and 47 were female ranging in age from 10-74 years (mean 44.2+/-12.4 years). The signals from lead I, surface averaged lead and esophagus averaged lead were amplified (up to 100 microV/cm), filtered (0.1-50 Hz), AD converted to 16-bit accuracy at a sampling rate of 2 KHz and averaged by using the three channel low-noise amplifier. The signal averaged esophageal sinus node potentials are deflections of low-amplitude and low-frequency preceding the P wave. Two morphologies, the domed wave (64 of 106 patients, 60%) and the smooth upstroke slope (42 of 106 patients, 40%), can be seen. The directly recorded sinoatrial conduction time was 82.3 +/-18.6 msec (mean+/-2 SD), ranged from 23-112 msec, amplitude was 3.8-27.7 microV and dv/dt was 0.42-1.92 mV/sec. The sinoatrial conduction time recorded by the transesophageal catheter technique was comparable to that (80.4+/-18. 1 msec) recorded by the transvenous catheter method perfectly. We think that signal averaged sinus node electrogram could be recorded in sinus rhythm in most patients with normal sinus node function and proper filter settings, high amplification and anti-drift technique are important in recording signal averaged esophageal sinus node electrogram. 

    The esophageal-ECG; New applications with a new technique. Maechler H, Lueger A, Huber S, Bergmann P, Rehak P, Stark G: The Internet Journal of Thoracic and Cardiovascular Surgery 1999; Vol2 (2), 1999. http://www.ispub.com/journals/IJTCVS/Vol2N2/esoecg.htm. Introduction: Because of suboptimized techniques, concerning leads and amplification methods, the esophageal ECG was thus only used to detect atrial arrhythmias. The esophageal ECG would be suitable for detecting intraoperative myocardial ischemia.  Methods: The esophageal ECG signals are detected with a bipolar esophageal probe. The signals are passed to a new high-resolution preamplifier (frequency range 0.01-2000 Hz), further on to an analog-digital-board and finally are visualized on a PC for definite evaluation.  Results: Compared with the surface ECG, the esophageal ECG could detect significantly more ischemic episodes in both, an animal comparison study (93% versus 47%) (n = 18), as well as in coronary artery bypass graft ( CABG) surgery. At the beginning of anesthesia 85 % of the high risk CABG patients showed ischemic episodes with the esophageal ECG (18% detection rate with the surface ECG), which were correlated with an adverse postoperative outcome (p<0.05). In addition to that, 8 of 18 CABG patients had a mean of 483 ± 119 high-amplitude, biphasic atrial components during cardioplegia (on the surface ECG, only one patient showed 26 P-potentials). Such atrial activities, visually not detectable, were correlated with postoperative supraventricular arrhythmias in 88 %.  Conclusions: The clinical relevance is that the esophageal ECG represents a convenient technique with high sensitivity, to monitor intraoperative myocardial ischemia and to detect atrial activity during cardioplegia.

    Left ventricular tachycardia in structurally inconspicuous cardiac findings. Gass M, Kühlkamp V, Mewis C, Baden W, Apitz J. Monatsschrift Kinderheilkunde 145(10):1051-1053, 1997. We report about the possibility of electrophysiological diagnosis and therapy in the treatment of a symptomatic left ventricular tachycardia which could not be treated effectively by oral medical therapy in a 10 year old boy with no obvious structural heart disease. By right bundle-bloc-like QRS-complexes in the surface-ECG, the diagnosis of the ventricular origin of the tachycardia was confirmed by transesophageal-ECG. This was followed by the first electrophysiological examination that showed increased left ventricular vulnerability. During this electrophysiological examination the tachycardia was terminated by stimulated singular premature beats. An oral medical therapy with sotalol was started. After the phase of saturation the next ventricular stimulation was done, that showed no sufficient protection of sotalol against VT. So the decision was made for ventricular ablation. After 5 high frequency-applications no furhter ventricular tachycardia could be induced. Since this intervention the patient lives without symptoms

    Esophageal electrocardiography in acute cardiac care. Efficacy and diagnostic value of a new technique. Shaw M, Niemann JT, Haskell RJ, Rothstein RJ, Laks MM. Am J Med 1987 Apr;82(4):689-96. Esophageal electrocardiography can detect atrial electrical activity during tachyarrhythmias when P waves are not evident by surface electrocardiography. However, patient discomfort, the difficulty of accurately interpreting cardiac signals against a background of electrical noise, and the complexity of use have limited widespread application. In this study, esophageal electrocardiography was used in 48 acutely ill patients with a new "pill electrode" system, consisting of a bipolar electrode pair (3 by 20 mm) attached to 0.5 mm diameter Teflon wires contained in a standard gelatin capsule. The capsule with enclosed electrodes was voluntarily swallowed, and the recording electrodes were positioned posterior to the left atrium. A preamplifier system with a low-frequency filter and a standard three-channel electrocardiographic recorder were used. Esophageal "pill" electrocardiographic recordings were made in 48 of 50 eligible study patients (96%) with tachyarrhythmias and absent or equivocal atrial activity on surface electrocardiography. In these patients, a high-quality esophageal electrocardiographic recording was obtained within one to 10 minutes with minimal patient discomfort. In 25 of 48 study patients (52%), the original diagnosis, based on the surface electrocardiographic recording, was incorrect after review of the esophageal recording. Results of esophageal recording altered management in 19 of 48 (40%) patients. This new and simple technique facilitates diagnosis and management of perplexing tachyarrhythmias in acutely ill patients by physicians with minimal training in the technique. 

    Esophageal lead for intraoperative electrocardiographic monitoring. Kates RA, Zaidan JR, Kaplan JA. Anesth Analg 1982 61(9):781-5. The use and safety of the esophageal electrocardiogram for detection and diagnosis of dysrhythmias or ischemia during anesthesia was compared with the conventional electrocardiogram using leads II and V5 in 20 patients undergoing coronary artery bypass graft surgery. Using an intra-atrial electrocardiogram as the standard to provide detection and definitive diagnosis of dysrhythmias, the correct diagnosis from leads II and V5 was made in 53.8% and 42.3% of cases, respectively, whereas 100% of the dysrhythmias were properly diagnosed from the esophageal electrocardiogram (p less than 0.05). In two patients, the presence of a significant dysrhythmia was not detected using standard leads II and V5 alone. Large, distinct P waves, resulting from the proximity of the esophageal lead to the left atrium, clearly established the temporal relationship between atrial and ventricular depolarization. Posterior myocardial ischemia was diagnosed in one patient by ST-segment elevation in the esophageal electrocardiogram, whereas leads II and V5 did not demonstrate ischemic changes. No complications were encountered during the study. The esophageal lead is safe, simple to use, and provides valuable information for detection or diagnosis of dysrhythmias and myocardial ischemia during anesthesia.

    Atrial flutter in infancy: diagnosis, clinical features, and treatment. Dunnigan A, Benson W Jr, Benditt DG. Pediatrics 1985 Apr;75(4):725-729. The clinical features and treatment of atrial flutter in eight infants (four male and four female) less than 2 months of age are presented. Atrial flutter was noted during the first week of life in six of the infants and between 6 and 8 weeks of life in the other two infants. Four of the eight infants had associated structural or functional cardiovascular disease, and in three infants a central venous pressure catheter was present in the atrium at the time atrial flutter was diagnosed. Classic flutter waves were apparent on 12-lead ECGs in only two infants. In six infants, flutter waves were not obvious on standard ECGs, but transesophageal electrogram recordings demonstrated the presence of atrial flutter with second degree atrioventricular block. The atrial cycle length during flutter ranged from 135 to 180 ms (mean 149 ms; mean atrial rate 403 beats per minute); there was a 2:1 ventricular response to atrial flutter. Successful termination of atrial flutter was accomplished using three modes of electrical cardioversion in seven of the eight infants: direct current cardioversion in one, transvenous atrial pacing in one, and transesophageal atrial pacing in five. One asymptomatic infant converted to normal sinus rhythm 24 hours following digoxin administration. One infant had multiple atrial flutter recurrences and required chronic procainamide therapy. In seven of the eight infants, no recurrences have been noted in 6 months to 3 1/2 years of follow-up. These results demonstrate that atrial flutter may be difficult to diagnose in infants with tachycardia unless transesophageal electrogram recording is utilized for evaluation.

    Clinical correlates of dysrhythmias requiring an esophageal ECG for accurate diagnosis in patients with congenital heart disease. Bushman GA. Arkansas Children's Hospital. J Cardiothorac Anesth 1989, 3(3):290-4. Esophageal electrocardiography (EsECG) is a useful adjunct in the diagnosis of dysrhythmias that are difficult to diagnose with a conventional ECG. This study was designed to evaluate which type of dysrhythmias required the EsECG for proper diagnosis and what factors produced the rhythm problems. Sixty-eight pediatric patients undergoing cardiac surgery were studied. After release of the aortic cross-clamp, the cardiac rhythm was analyzed by a standard limb-lead ECG at five-minute intervals. Twenty-six of 68 patients exhibited rhythms during reperfusion that required the EsECG for definitive diagnosis. This group of patients was younger, had longer durations of cardiopulmonary bypass and aortic occlusion, and required more time and interventions to achieve a normal sinus rhythm. The likelihood of difficult dysrhythmias was not related to the type of surgical procedure performed.

    Value of the esophageal approach in the diagnosis, treatment and therapeutic surveillance of arrhythmia in children. Moquet B, Chantepie A, Fauchier JP, Cosnay P, Huguet RG, Laugier J. Service de Cardiologie B, CHU Trousseau, Tours. Arch Fr Pediatr 1989 Jan;46(1):11-7. For the past few years, a new method for the investigation and treatment of arrhythmias has been used: transoesophageal atrial pacing and recording (TAPR). In the light of 6 cases observed recently, we review the technical aspects and the indications for TAPR. A bipolar stimulation catheter is inserted in the oesophagus and positioned in the area where the atrial wave of greater amplitude is recorded. Atrial stimulation is done with impulses of long duration obtained with a special stimulator. Two cases validated this technique which was effective to correct atrial flutter in a neonate with heart failure resistant to medical treatment as well as in a 5 year-old child. The value of TAPR as a diagnostic tool in cases of tachycardia is discussed in the context of 2 cases: a 5 week-old with wide QRS and a 14 month-old with narrow QRS. Finally, the value of TAPR for monitoring the efficacy of anti-arrhythmia medications is illustrated by 4 cases of supraventricular tachycardia, in whom the optimal dosage of the anti-arrhythmic drug used was determined with the help of TAPR-induced tachycardia. The current literature concerning the technique, indications and results of TAPR are reviewed. This method is likely to take a great importance for the study and treatment of supraventricular arrhythmias in children.

    Esophageal ECG recording--a valuable diagnostic tool in dual chamber pacing. Brandt J, Pahlm O, Schuller H. Eur Heart J 1985 Apr;6(4):342-8  The interpretation of the ECG of a dual chamber pacemaker necessitates the identification of atrial activity. This is a prerequisite for the evaluation of pacemaker function and for the correct adjustment of programmable pulse generators. The assessment of atrial capture in standard 12-lead ECGs is, however, sometimes rather difficult. Esophageal ECG recording by means of a reusable unipolar electrode, inserted transnasally, and connected to a standard ECG recorder, is a simple, rapid and inexpensive method for the reliable identification of P-waves. Clinical examples are presented to illustrate the value of this technique in determining atrial capture and as a tool for the differential diagnosis of pacemaker-involved tachycardias. The use of esophageal ECG recording in the clinical follow-up of patients with dual chamber pacemakers is recommended.

    Utilization of programmers to measure interatrial conduction times and to program individual AV delay in DDD pacemaker patients. B. Ismer (1), G. H. von Knorre (1), W. Vo?(1), W. Grille (2). (1) Universität Rostock Klinik und Poliklinik für Innere Medizin Abteilung Kardiologie Postfach 100888 D-18055 Rostock (2) Medizinische Klinik Städtisches Krankenhaus Kiel Chemnitzstr.33 D-241161 Kiel. Herzschrittmachertherapie und Elektrophysiologie. 9(4), 260-269, 1998. Background: In patients with DDD pacing systems, optimal AV delay is mainly determined by interindividually differing interatrial conduction time. If the latter is measured, individual optimal AV delay in VDD and DDD operation can be approximated by adding a representative, optimal interval of 70ms between left atrial depolarization and ventricular stimulus. In modern pacemakers providing telemetry, combination of right atrial telemetry and left atrial electrography via an esophageal lead could be used to measure interatrial conduction times for individual AV delay programming. Aims of the study: 1. To test the usefulness of telemetric right atrial electrograms and markers as a right atrial measuring reference. 2. To prove the possibility of implementing left atrial electrography into commercial programers. Methods: 1. Using computerized heart simulator, delays of the telemetric electrogram and markers were investigated in 12 DDD systems of 9 different companies. 2. To measure interatrial conduction times with programers, simultaneous recordings of right atrial electrogram and marker channel, resp., and the left atrial electrogram were performed using external hardware or internal software filtering of the esophageal lead. Results: Depending on the range of marker delay, pacing systems with real-time telemetry (delay 0-12ms) and orienting telemetry (delay \gg12ms) were found. Facilitating left atrial electrogram recording into programers, interatrial time intervals can be measured in DDD and VDD operation in pacing systems with real-time telemetry. These results are prerequisits for individual AV delay programming with the programer. Then both can automatically be proposed, basic AV delay and the frequency modulated AV delay. Conclusion: Facilitating left atrial electrogram recording into pacemaker programers, interatrial conduction times can easily be measured for simplified physiologic AV delay programming during routine check-up. 

    Transesophageal pacing and recording. Takenaka S, Ohe T. Okayama University Medical School. Nippon Rinsho 1996 Aug;54(8):2074-9. Identification of P wave is essential for the diagnosis of various arrhythmias. The transesophageal ECG is useful for obtaining the relationship of atrial-ventricular activation when P wave is difficult to recognize on the surface ECG. Transesophageal pacing is also helpful to evaluate the function of the conduction system and to clarify the mechanism of arrhythmias. Thus, transesophageal pacing and recording can be used as beside electrophysiologic studies in patients with sick sinus syndrome, atrial-ventricular block, atrial flutter, and paroxysmal supraventricular tachycardia.

    Utility of the filtered bipolar esophageal lead in the diagnosis of arrhythmias. Ishinaga T, Komatsu C. Jpn Circ J 1984 Dec;48(12):1289-98. Electrophysiologic study was performed in 25 patients with tachycardia or bradycardia attacks. The coronary sinus (CS) and filtered bipolar esophageal electrograms were recorded simultaneously to compare the phase of atrial activations. During sinus rhythm and high right atrial pacing, the esophageal and proximal CS atrial activations were nearly simultaneous but earlier by 26 +/- 5 msec on the average than the distal CS atrial activations. During reciprocating tachycardia due to reentry using a left-side accessory atrioventricular pathway for retrograde conduction the esophageal and CS atrial activations occurred earlier than the low septal right atrial activation, so the esophageal lead can be used as a substitute for the CS lead to clarify the eccentric retrograde atrial activation sequence. By using the filtered bipolar esophageal lead, the interval from Q wave on the surface electrocardiogram to the first rapid deflection in the esophageal atrial activation (Q-AESO interval) was measured in 15 patients with supra-ventricular tachycardia. All patients with reciprocating tachycardia due to reentry using a left side accessory atrioventricular pathway had Q-AESO intervals between 100 to 130 msec and four of five patients with a right side accessory atrioventricular pathway for retrograde conduction had Q-AESO intervals between 130 to 150 msec. In contrast, all patients with reentry in the atrioventricular node had Q-AESO intervals between 30 to 60 msec. The esophageal lead is also of value in the prompt diagnosis of atrial flutter and ventricular tachycardia, since the esophageal electrograms readily reveal the relationship between atrial and ventricular activations. In conclusion, the filtered bipolar esophageal lead provides a non-invasive method for the quick diagnosis of various arrhythmias.

    Atrial electrogram monitoring in a cardiac care unit. Mantle JA, Strand EM, Wixson SE. Med Instrum 1978;12(5):289-92   Routine monitoring of a bipolar atrial electrogram (AEG) simultaneously with the electrocardiogram is a useful and safe clinical technique for the diagnosis of complex cardiac dysrhythmias. The large-amplitude A waves of the AEG can be more reliably identified than the corresponding low-amplitude p waves of the electrocardiogram. Epicardial wires placed during cardiac surgery, catheter-mounted endocardial electrodes, and esophageal electrodes can all be used for routine AEG monitoring. A multipurpose pulmonary arterial catheter with a pair of electrodes, and esophageal electrodes can all be used for routine AEG monitoring. A multipurpose pulmonary arterial catheter with a pair of electrodes mounted on the proximal shaft can be used for combined AEG and hemodynamic monitoring. The equipment needed for AEG monitoring and recording consists of an additional bedside amplifier with 12- to 100-Hz band-pass filter, a dual-channel display scope, and a dual-channel strip chart recorder. Care must be used to keep the atrial electrodes electrically isolated for patient safety. In addition to enhancing the diagnosis and management of dysrhythmias, recording an AEG provides a signal that is suitable for automatic processing.

    A high-resolution esophageal electrocardiogram for monitoring atrial activity in the hypothermic potassium-arrested heart. Maechler HE, Lueger A, Bergmann P, Friehs I, Stark G, Berger J, Anelli-Monti M, Rehak P, Rigler B. Karl-Franzens University of Graz, Austria. Anesth Analg 1997, 84(3):484-90. Atrial electrical activities during hypothermic, K(+)-induced cardioplegic arrest correlate with an increased incidence of postoperative supraventricular dysrhythmias in coronary artery bypass graft patients. Surface electrocardiogram (ECG) (S-ECG) may be insufficiently sensitive to detect such activity intraoperatively, and invasive methods are impractical and traumatic. From induction of anesthesia until the end of surgery, esophageal ECG signals were detected with a new bipolar esophageal probe and a new high-resolution preamplifier (frequency range 0.01-2000 Hz). The S-ECG and the esophageal ECG (E-ECG) were evaluated independently in 18 patients. Eight of 18 patients presented during cardioplegic arrest a mean of 483 +/- 119 high-amplitude, biphasic P components (mean amplitude 0.7 +/- 0.1 mV, range 0.35-1.15 mV) per patient (mean 36 +/- 6 [5-59] potentials/min) similar to those coinciding with the surface ECG P-waves during sinus rhythm. Six of these eight patients presented a mean of 29 +/- 11 low atrial activities (mean amplitude 0.14 +/- 0.023 mV; range 0.1-0.25 mV) per patient (mean 8.4 +/- 5.6 [2.3-48] potentials/min) in the E-ECG. In the S-ECG, one patient of these eight presented 26 P waves during cardioplegic arrest simultaneously with activities in the E-ECG. During the first 5 days, seven of eight (88%) patients with atrial activities in the E-ECG versus 3 of 10 (30%) patients without atrial activities developed supraventricular tachyarrhythmias postoperatively (P < 0.05). This new high-resolution E-ECG device detected in a beat-to-beat technique more atrial activity during cardioplegic arrest than a S-ECG and offered the advantages of artifact exclusion and better prediction of postoperative supraventricular dysrhythmias.

    A new high-resolution esophageal electrocardiography recording technique: an experimental approach for the detection of myocardial ischemia. Machler HE, Lueger A, Rehak P, Berger J, Veith W, Kuhbacher C, Koidl C, Stark G, Metzler H. Karl-Franzens University of Graz, Austria. Anesth Analg 1998;86(1):34-9. Criteria for ischemic changes in the esophageal electrocardiograph (E-ECG) have not been standardized and validated. The main goal of this study was to evaluate the experimental esophageal recording of myocardial ischemia and to assess the association between ST segment alternans in the E-ECG and ischemia. Experiments were performed on 18 anesthetized sheep with occlusion of a branch of the left anterior descending artery. The bipolar signals were recorded via an esophageal lead containing three chloridized silver electrodes. Electrical signals were amplified in a self-designed, battery-supported preamplifier (gain 1000, frequency range 0.01-2000 Hz, common mode rejection 140 dB, signal noise 5-7 microV p-p), then sent to a digital oscilloscope for display and to a pulse code-modulated recorder. Surface electrocardiography (S-ECG) data were also recorded. Ischemia E-ECG revealed homogenous ST segments without any beat-to-beat alternans. Two minutes after occlusion, 14 of 15 sheep (93%) showed repetitive beat-to-beat fluctuations within the ST segment on the E-ECG. Of the 15 sheep, 7 (47%) showed ischemia in the S-ECG (P < 0.01). For calculation of the dynamic changes in the ST segment in the E-ECG, the difference in the amplitudes of the ST segment of five successive beats to the next beat, performed for 200 consecutive beats, was calculated. The central tendency of the sum of these values before versus during ischemia was 2000 mV/ms versus 5000 mV/ms (Hodges-Lehmann point estimator) (95% confidence intervals 1700/2500 versus 3350/9250 [lower limit/upper limit]). The authors have established a close temporal relationship between the magnitude of ST segment alternans recorded via E-ECG and myocardial ischemia. Implications: The study presents the use of an esophageal electrocardiograph for detection of progressive changes of myocardial ischemia and infarction. During acute myocardial ischemia and infarction in sheep, the esophageal electrocardiograph has visually apparent ST alternans of amplitude in the millivolt range, in part due to a special amplifier (0.01-2000 Hz). This is therefore one very promising technique for better evaluation of electrocardiographic changes of ischemia. 

    The role of esophageal leads in the detection of exercise-induced postero-basal ischemia. Mittal SR, Sethi JP, Sharma D. J.L.N. Medical College, Ajmer, Rajasthan, India. Int J Cardiol 1989 Apr;23(1):69-77. The effects of maximal hyperventilation and submaximal exercise were studied on the unipolar, esophageal electrocardiogram recorded at ventricular level in 25 'normal' persons and 15 patients having ischemic heart disease with a positive exercise stress test. In normal persons, hyperventilation decreased the amplitude of the R and T waves in 10 and 6 cases, respectively. Submaximal exercise increased the height of the P wave in 8 cases, decreased the amplitude of the R wave in 16 cases and increased the depth of the S wave in 10 cases. In patients with established ischemic heart disease, the esophageal lead could detect exercise-induced posterior ischemia in 8 cases when compared to lead V8, which could detect posterior ischemia in only 3 cases. It is inferred that the esophageal lead placed at the ventricular level is much more sensitive in detecting exercise-induced posterobasal ischemia. Lack of facilities for coronary angiographic and exercise thallium scintigraphic studies limited us from correlating this study and thereby establishing its independent usefulness.

    Diagnostic value of the bipolar esophageal electrocardiographic lead for detection of disorders of cardiac rhythm and conductivity at rest, during physical exercise and with Valsalva's maneuver. Lukoshiavichiute AI, Gedrimene DA, Shvela G, Bishoff K. Kardiologiia 1988 Feb;28(2):17-9. Diagnosis of some heart rhythm disorders is based on bipolar esophageal ECG lead that can detect a P wave of greater amplitude, as compared to the QRS complex. The diagnostic value of bipolar esophageal ECG lead is in that it provides a more reliable assessment of pacemaker localization (both nomotopic and heterotopic), the sinoatrial node rhythm, extrasystole localization, type and mechanism of paroxysmal tachycardias, as well as antegrade and retrograde (ventricle-to-atrium) impulse conduction. Bipolar esophageal ECG lead records contribute to correct assessment of cardiac rhythm and conductivity disorders at rest as well as during exercise and Valsalva's test.

    Prediction of permanent atrial sensing by preoperative esophageal atrial wave evaluation. Vrouchos G, Kiupeloglou G, Laguvardos P, Kondopodis M, Fragiadulakis G. CCU, Venizelion District General Hospital, Heraklion, Crete, Greece. Pacing Clin Electrophysiol 1992 Nov;15(11 Pt 2):1957-61. Atrial undersensing is a common problem in permanent atrial and dual chamber pacing. The purpose of this study was to evaluate the relationship between transesophageal atrial wave (EsAW) and right atrial endocavitary (RA). Forty-seven patients 72 +/- 9.7 years of age, with symptomatic bradyarrhythmias were studied. The EsAW was filtered with a high pass filter of 10 Hz (Arzco preamplifier-filter), using 1, 2, and 3 cm bipolar transesophageal catheters. Atrial bipolar floating 1, 2, and 3 cm electrograms from the high RA (HRA) and from the mid RA (MRA), as well as unipolar electrograms from the right auricle (RAUR) were recorded 1 day later. Comparison by paired t-test showed no significant differences between EsAW and bipolar sensing in RA, but significant differences between EsAW and RAUR (P = 0.0001). The results of the Spearman correlation coefficient for sensing (mV) for EsAW, HRA, and MRA, respectively, were: 1 cm, 1.8 +/- 0.9, 1.7 +/- 0.9, and 1.9 +/- 0.9 (z > 3.5; P < 0.0003); 2 cm, 2.2 +/- 0.9, 1.9 +/- 0.8, and 2.1 +/- 0.9 (z > 2.3; P < 0.03); 3 cm, 2.1 +/- 1, 2 +/- 0.9, and 2.2 +/- 1.0 (z > 2.9; P < 0.003); and the result for the monopolar RAUR was 3.0 +/- 1.0 (z < 1.4; P > 0.17). These findings, if confirmed in more patients, indicate that preoperative EsAW recording could be useful in estimating the quality of bipolar floating electrograms from the RA but not of unipolar RAUR.

    Comparative assessment of the diagnostic value of intracardiac and transesophageal electrophysiological examination of patients with reciprocal atrioventricular tachycardia caused by additional atrioventricular junctions. Sulimov VA, Papakin GM, Preobrazhenskii VIu, Kuz'menkov DV, Syrkin AL. Kardiologiia 1988;28(2):11-7. Thirty patients with frequent attacks of supraventricular tachycardia were investigated, and a reciprocal paroxysmal atrioventricular tachycardia due to additional atrioventricular junctions was diagnosed in 16 of those. Heart rhythm disorders were rooted in the apparent Wolff-Parkinson-White syndrome in 8 patients, and in its latent variety in another 8. A comparative assessment of diagnostic potentials of esophageal and intracardiac electrophysiologic investigation demonstrated the latter to be an effective method for provoking reciprocal atrioventricular tachycardias and allow a reliable assessment of basic antegrade refractory periods and intervals of the heart's conductive system, including the effective refractory period of Kent's bundle, in patients with additional atrioventricular junctions. In esophageal electrophysiologic studies, electrographic V-A interval exceeding 90 ms during an attack of tachycardia is a major sign of reciprocal atrioventricular tachycardia due to additional atrioventricular junctions.

    Study of P wave morphology in lead V1 during supraventricular tachycardia for localizing the reentrant circuit. Brembilla-Perrot B. Chu of Brabois, Vandoeuvre, France. Am Heart J 1991;121(6 Pt 1):1714-20 . Paroxysmal supraventricular tachycardia (SVT) is a benign form of tachycardia that generally does not require costly evaluation. The purpose of this study was to describe a new sign permitting delineation of the mechanism of SVT by analysis of the P wave in lead V1 and the left atrial electrogram, which may be registered by the esophageal electrode. Among 146 patients with SVT, 72 had a ventriculoatrial interval greater than 70 msec. The P wave in lead V1 during SVT was discernible in 69 of them. The precession of the left atrial electrogram on the P wave in lead V1 was always associated with reentry through a left lateral (n = 37) or posteroseptal (n = 4) accessory atrioventricular (AV) connection. When the P wave in lead V1 preceded or occurred simultaneously with the left atrial electrogram, reentry was through either the AV node or a right-sided accessory AV connection. On the other hand, although the P wave in lead V1 was more frequently negative in reentry through a right-sided connection and positive in reentry through a left-sided connection, the polarity was not specific enough to identify the reentry. The precession of the left atrial electrogram recorded by the esophageal electrode on the P wave in lead V1 during SVT was a specific criterion of reentry through a left accessory AV connection, and this technique could be useful for preliminary localization of the accessory connection before electrophysiologic study. 

    Value of esophageal pacing in evaluation of supraventricular tachycardia. Brembilla-Perrot B, Spatz F, Khaldi E, Terrier de la Chaise A, Le Van D, Pernot C. Division of Cardiologie A, CHU Brabois, Vandoeuvre-Les-Nancy, France. Am J Cardiol 1990;65(5):322-30. Esophageal stimulation was performed in 40 patients who had spontaneous paroxysmal supraventricular tachycardias (SVTs). The purpose of this study was to look for the most sensitive stimulation protocol and criteria that would help to define the mechanism of reentry. In 20 patients (group I) atrial pacing up to second-degree atrioventricular block was performed under control conditions and isoproterenol, and SVT was induced in 14 patients (70%), 11 in the control state and 3 while receiving isoproterenol. In 20 patients (group II) atrial pacing and programmed atrial stimulation using 1 and 2 extrastimuli delivered at 2 cycle lengths (600 and 500 ms) was performed in the control state and while receiving isoproterenol. SVT was induced in all patients, in 13 patients in the control state and in 7 while receiving isoproterenol. Programmed stimulation always induced SVT and was the only method capable of tachycardia induction in 14 patients. The mechanism of SVT could be established in 91%. The measurement of the ventriculoatrial interval was the most useful sign to define the site of reentry. Occurrence of a bundle branch block helped to delineate the mechanism in 4 patients. When a positive P wave in V1 preceded the esophageal atrial electrocardiogram, it suggested that there was reentry through a left-sided accessory atrioventricular connection in 6 patients. SVT could always be induced by programmed atrial stimulation in the control state and under isoproterenol. The location of the P wave in V1 compared to the ventriculogram and the esophageal electrocardiogram helped to define the mechanism of tachycardia.

    Use of the esophageal lead in the diagnosis of mechanisms of reciprocating supraventricular tachycardia. Gallagher JJ; Smith WM; Kasell J; Smith WM; Grant AO; Benson DW Jr Pacing Clin Electrophysiol, Jul 1980, 3(4) p440-51. Recent studies have emphasized the role of concealed accessory pathways in reciprocating supraventricular tachycardia. Diagnosis has generally required multicatheter electrophysiologic study. We recorded esophageal electrograms during study in 16 patients with reciprocating tachycardia due to reentry using an accessory atrioventricular pathway, and in 12 patients with reciprocating tachycardia due to reentry in the AV node. The interval from onset of ventricular depolarization to earliest atrial activation (V-AMIN), earliest atrial activity on the esophageal lead (V-AESO), and high right atrium (V-HRA) was measured. No patient with RT due to an accessory atrioventricular pathway had a V-AMIN or V-AESO less than 70 ms, or a V-HRA less than 95 ms. In contrast, 11 of 12 patients with reentry in the AV node had V-AESO intervals less than 70 ms. Esophageal recording during reciprocating tachycardia provides a simple screening procedure available to all practicing physicians to exclude the diagnosis of accessory atrioventricular pathways in the genesis of paroxysmal supraventricular tachycardia. 

    Effect of intravenous propranolol or verapamil on infant orthodromic reciprocating tachycardia. Silberbach M, Dunnigan A, Benson DW Jr. Variety Club Children's Hosp, U of Minnesota. Am J Cardiol 1989;63(7):438-42. The effects of intravenous verapamil (0.15 mg/kg) and propranolol (0.2 mg/kg) with regard to atrioventricular (AV) conduction and tachycardia termination during paroxysmal atrial tachycardia were compared in 2 groups of infants (verapamil n = 14, propranolol n = 18, mean age 80 +/- 21 days, range 1 to 364). Using transesophageal recording techniques, tachycardia cycle length, AV intervals and ventriculoatrial intervals were measured before and after drug administration. Both intravenous propranolol and verapamil significantly prolonged tachycardia cycle length and AV interval (cycle length--propranolol 230 +/- 30 to 262 +/- 33 ms, p less than 0.05, verapamil 223 +/- 38 to 245 +/- 32 ms, p less than 0.05; AV interval--propranolol 98 +/- 26 to 126 +/- 38 ms, p less than 0.05, verapamil 96 +/- 19 to 109 +/- 24 ms, p less than 0.05). Neither drug prolonged the ventriculoatrial interval. Tachycardia terminated after intravenous verapamil in 11 of 14 infants (79% efficacy rate). Tachycardia terminated in 0 of 18 after intravenous propranolol (0% efficacy rate). In 8 infants an atrial deflection was recorded on the esophageal electrocardiogram at the time of tachycardia termination after intravenous verapamil, which suggested that tachycardia terminated by block occurring in the AV node. In 2 infants a ventricular deflection was recorded at the time of tachycardia termination after verapamil, which suggested that block occurred in the accessory connection. Both drugs prolonged tachycardia cycle length by prolonging AV conduction to a similar degree.

    Noninvasive evaluation of supraventricular tachycardias. Shenasa M, Nadeau R, Savard P, Lemieux R, Curtiss EI, Follansbee WP. U. of Pittsburgh School of Med.Cardiol Clin 1990 Aug;8(3):443-64. In this article we discuss the role of noninvasive methods in evaluation of supraventricular tachycardias. The limitation of Holter monitoring and exercise testing is discussed. A significant portion of the article is devoted to the role of esophageal recording, body surface potential mapping, and phase image analysis, areas that are often underutilized but that have potential in the diagnosis of supraventricular tachycardias.

    Early detection of myocardial ischemia in hypertensive patients using exercise esophageal electrocardiography. Mittal SR, Sharma D, Garg D. J.L.N. Medical College and Hospital, Ajmer, India. Int J Cardiol 1990 Feb;26(2):236-7. Effects of submaximal exercise were studied on the unipolar esophageal electrocardiogram recorded at ventricular level in 15 patients with essential hypertension who complained of chest discomfort on effort but had negative exercise stress tests using standard leads and lead CM5. Six patients developed horizontal or downsloping depression of the ST segment in the esophageal lead. The ischemic response might result from subcritical coronary stenosis in face of the increased myocardial oxygen demand of hypertrophied myocardium.

    Estimation using unipolar transesophageal recording of the interatrial conduction time in patients with paroxysmal atrial flutter and fibrillation. Simoncelli U, Marchetti A, Sorgato A, Rusconi C. Minerva Cardioangiol 1991 Jun;39(6):219-25. Twenty-three consecutive subjects (age 46.7 +/- 21, range 13-78) addressed to our attention for symptoms attributed to documented or suspected supra ventricular arrhythmias underwent transesophageal electrophysiologic study. On the basis of the preliminary investigations 15 proved free from organic heart disease, 2 were affected with ischemic heart disease (secondary angina), 6 with hypertensive cardiomyopathy. In each patient the sensibility, specificity and positive predictive value of the following reports regarding the occurrence of paroxysmal fibrillation and flutter (Ffap) were evaluated: a) echo reports of left atrial enlargement; b) ECG signs of atrial enlargement; c) interatrial conduction time (TCIA) assessed with unipolar transesophageal recording. As TCIA we adopted the time interval intercurrent from the first low-voltage deflection of the esophageal P wave (far field) and the apex of the intrinsecoid deflection of the same wave. TCIA proved significantly longer in the 12 patients affected with Ffap compared with those free from documented paroxysmal or inducible arrhythmias or affected with paroxysmal junctional reciprocating tachycardias: 76.6 +/- 11 vs 51.8 +/- 11.7; p less than 0.001. A TCIA greater than 63 msec characterizes with satisfactory sensibility and specificity the occurrence of Ffap: sens. 75%, spec. 91%, positive predictive value 90%. Echo and ECG reports of atrial enlargement behave as highly specific but not sufficiently sensitive indexes of the occurrence of Ffap: sens. 42%, spec. 100%, pos. pred. val. 100% and sens. 17%, spec. 100%, pos.pred.val. 100% resp. We concluded that TCIA is an index correlated with and predictive of the occurrence of Ffap in patients symptomatic for cardiopalmus or neurologic symptoms in the absence of other arrhythmias detectable with Holter monitoring which are able to produce clinical symptoms.

    Transesophageal electrocardiography and atrial pacing in acute cardiac care: diagnostic and therapeutic value. Twidale N, Roberts-Thomson P, Tonkin AM Flinders Medical Centre, Bedford Park, SA. Aust N Z J Med 1989 Feb;19(1):11-5. The utility of transesophageal electrocardiography using a bipolar 'pill electrode' was assessed in 17 consecutive patients with tachycardia presenting to our casualty department. Standard 12-lead electrocardiography showed regular narrow QRS tachycardia in 12 patients, and five patients had wide QRS tachycardia. Esophageal atrial electrogram recordings were obtained in 14 patients (82%), and these were helpful in determining the mechanism of tachycardia in 11 patients (78%). Of these 11, seven patients fulfilled criteria for atrioventricular junctional (AVJ) tachycardia based on measurement of the minimum interval between the onset of ventricular depolarisation and earliest atrial (esophageal) activity. One of these patients had presented with a wide QRS tachycardia. The other four patients were diagnosed as having ventricular tachycardia (VT) following diagnosis of AV dissociation. Atrial overdrive pacing, via the pill electrode, successfully reverted four of the nine patients (44%) with narrow QRS tachycardia but no patient with VT. Esophageal recording during tachycardia is a simple, relatively non-invasive technique which is helpful in suggesting the mechanism of tachycardia both in patients with narrow and wide QRS tachycardia, and may have a therapeutic role in patients with AVJ tachycardia.

    Electrophysiologic study of concealed accessory A-V pathway. Guo CY, Sun RL, Chen X. Chung Hua Nei Ko Tsa Chih 1989 Feb;28(2):85-8, 126. The presence of concealed accessory A-V pathways (CAP) was demonstrated in 14 out of 18 (78%) patients with supraventricular tachycardia (SVT) and narrow QRS complexes. Such a high percentage of CAP mediated AVRT is a quite unique finding. The importance of a standard programmed electrical stimulation protocol in documenting CAP is emphasized. Careful atrial mapping and premature ventricular stimulation during SVT are very helpful for diagnosis and localization of CAP. We considered that a V-A interval of 75 ms or more on intracardiac electrogram or a R-P interval of 85 ms or more on esophageal electrogram is a good criterion for AVRT utilizing an accessory pathway.

    The pill electrode. New technology as an adjunct to nursing assessment of patient arrhythmias. Quaal SJ, Phillips B, Howery T, Jadvar H. Prog Cardiovasc Nurs 1989 Jan-Mar;4(1):10-7 . The value of esophageal electrocardiography (ECG) in differential diagnosis of complex arrhythmias has been well known for the past half century. However, until recently, the technique was not widely used primarily because of the patient discomfort associated with esophageal placement of nasogastric tubes containing the ECG electrodes. With the advent of the pill electrode and development of appropriate recording methodology, interest in and use of esophageal electrocardiography has increased dramatically. In this article, the authors review the historic development of the pill electrode, recording technique, and current case studies in which the technique of pill electrode esophageal ECG monitoring facilitated differential diagnosis of complex arrhythmias.

    Atrio-ventricular conduction in patients with permanent right-ventricular stimulation. I. Possibilities of evaluation by the method of transesophageal electrocardiogram. Ciemniewski Z, Zajac T, Kargul W, Giec L.Kardiol Pol 1990 Feb;33(2):73-8. We analyzed 214 patients with permanent, VVI mode stimulation divided in 5 groups. Group I 89 patients (pts) with sick sinus syndrome (sss) (mean age 60 +/- 14 yrs), group II 21 pts with sss and atrioventricular (a-v) conduction disturbances (mean age 54 +/- 19 yrs), group III 72 pts with a-v block, but without intraventricular conduction disturbances (mean age 68 +/- 11 yrs), group IV 20 pts with a-v block and registered bundle branch block (mean age 67 +/- 7) and group V 12 pts after His bundle ablation (mean age 51 +/- 20 yrs). In all pts we recorded leads I, II, III, V1, V6 and oesophageal (oe) on Mingophon 7 (Siemens-Elema) with paper speed 50 mm/s. All recordings were performed during basic and magnetic rate of the pulse generator. We could analyzed ventriculo-atrial (v-a) conduction in group I-IV respectively in 89.9%, 95.3%, 84.7%, 100%, 83.3% and in all population in 89.2% cases. In 23 pts (10.8%) we could not analyzed v-a conduction due to atrial flutter or fibrillation. V-a conduction was present in groups I-IV in 61.2%, 35%, 21.4%, 45% and 10% cases respectively. Conclusions: 1. In group patients with sick sinus syndrome and VVI stimulation ventriculo-atrial conduction was recorded in most cases. 2. Ventriculo-atrial conduction was recorded in part of the population with atrio-ventricular block. 3. Frequency of ventriculo-atrial conduction phenomenon is dependent on degree of a-v block. 4. Transesophageal recording of ventriculo-atrial conduction phenomenon in patients with implantable VVI pacemaker is simple, noninvasive and useful method for clinical practice.

    Atrio-ventricular conduction in patients with permanent right-ventricular stimulation. II. Atrio-ventricular conduction time in patients with normal and impaired atrio-ventricular conduction. Ciemniewski Z, Zajac T, Kargul W, Giec L. Kardiol Pol 1990 Feb;33(2):79-83. We analyzed transesophageal ECG recordings of 79 patients (42 men and women aged 17-85 mean 61 +/- 16 yrs) with present ventriculo-atrial conduction phenomenon during permanent VVI stimulation. All measurements we performed on basic and magnetic rate of the pulse generator. V-a conduction time was defined as mean (from 5 measurements) time from spike of the pulse generator to the first deflection of P wave recorded from esophagus and expressed in miliseconds. We compared v-a conduction time (v-act) on basic and magnetic rates of a stimulator and between groups with normal (group A, 49 pts) and prolonged a-v conduction time (group B, 30 pts). Group B was divided on group B-1 (19 pts without bundle branch blocks) and B-2 (11 pts with bundle branch blocks during observations). V-act during magnetic rate (cycle 596 +/- 70 ms) was significantly longer than during basic rate (cycle 834 +/- 66 ms) (191 +/- 48 ms vs 185 +/- 44 ms, p 0.05). V-act in patients with a-v block (group B) was significantly longer than in patients with normal a-v conduction (group B) (219 +/- 45 ms vs 190 +/- 47 ms, p 0.02). The longest v-act was observed in group B-2 (236 +/- 32 ms). Conclusions: 1. Ventriculo-atrial conduction time could be measured in patients with permanent VVI stimulation using esophageal ECG recording. 2. Shortening of the stimulation cycle prolonges ventriculo-atrial conduction time. 3. Ventriculo-atrial conduction time is longest in group with atrio-ventricular conduction disturbances, especially in group with registered bundle branch block.

    Holter monitoring with a pill-shaped esophageal electrode. Sorgato A, Marchetti A, Simoncelli U, Rusconi C. G Ital Cardiol 1991 Jun;21(6):661-8. This study analyzes the possibility of using an oesophageal lead in the ambulatory ECG monitoring in order to improve the diagnostic effectiveness of the method by reliable identification of atrial activity. The oesophageal Holter monitoring was performed on 19 patients (pts) (8 F and 11 M, aged 34 to 79 years). These patients posed precise diagnostic problems unsolved by previous conventional Holter recordings. The oesophageal Holter recording was carried out with a Spacelabs recorder, model 90205 with two channels. One electrode was positioned in the standard lead CM5 and the second in the oesophagus using an Esodyn 2 electrode with a dynamic configuration made by C.B-Bioelettronica (Calenzano, Florence). The oesophageal lead was connected with the recorder by filter model EHF-4. The electrode was swallowed by the patient and the best position regulated on the P diphasic deflection of the highest amplitude. The monitoring allowed correct identification of the P wave over a 24-hour period. The arrhythmia which required the oesophageal Holter monitoring was recorded again in 15 of 18 patients examined. In each of these cases it was possible to solve the diagnostic question. The following arrhythmias were found: constant time correlation between the P deflection and the QRS in accordance with a supraventricular tachycardia with intraventricular conduction delay (4 pts); A-V dissociation in accordance with a ventricular tachycardia (2 pts); pause caused by atrioventricular block 2:1 (1 pt), second degree sinus-atrial block (1 pt), blocked premature atrial beats (4 pts); premature ventricular and premature atrial beats with intraventricular conduction delay (3 pts).

    Diagnostic approach to cardiac arrhythmias. Levy S. Cardiology Division, University of Marseille, France. J Cardiovasc Pharmacol 1991;17 Suppl 6:S24-31. The diagnostic approach to cardiac arrhythmias should be logical and starts with the clinical history, which provides two types of information: (a) the presence of symptoms, and (b) the clinical context, including the presence of an underlying heart disease. Clinical history and examination are helpful in the choice of pertinent invasive or noninvasive tests. The tolerance of the arrhythmia is not helpful in determining the type of arrhythmia because ventricular tachycardia, for example, may be well tolerated or even asymptomatic. The electrocardiogram (ECG) in sinus rhythm may be suggestive of the origin or etiology of arrhythmia as the presence, for example, of the Wolff-Parkinson-White pattern. An essential step in the diagnostic approach to arrhythmia is the ECG documentation. Ambulatory Holter monitoring, radiotelemetry, intermittent recorders, exercise testing, and electrophysiological testing will help in this endeavor. The latter is particularly useful in paroxysmal circus movement tachycardias. Once the tachycardia is recorded, a number of clues, including the regularity of the RR interval and the width of the QRS complex, may facilitate the diagnosis. In tachycardias with wide QRS complexes, preexcitation has to be excluded. The first step is then to look for atrioventricular dissociation, which is diagnostic of ventricular tachycardia. Other diagnostic clues (QRS duration, axis deviation, QRS morphology) may be useful. In case of difficulty because of preexisting bundle branch block or aberrancy, esophageal, right atrial, or His bundle recordings are indicated. If the tachycardia is not well tolerated, prompt termination with electrical DC shock should be performed.

    Left origin of the atrial esophageal signal as recorded in the pacing site. Bagliani G, Meniconi L, Raggi F, Corea L. Foligno General Hospital, Italy. Pacing Clin Electrophysiol 1998 Jan;21(1 Pt 1):18-24. Clear atrial depolarizations from inside the esophagus have always been recorded in electrocardiology, but their precise origin is still under discussion. Though atrial signals are recorded along most of the esophagus, pacing of the atria is possible only in a short tract, probably where the esophagus is in contact with the posterior left atrium wall. In order to ascertain which portion of atria gives rise to the esophageal atrial signal recorded in the atrial pacing segment, we examined 37 patients with normal P waves on the standard ECG by inserting esophageal and endocavitary catheters. The interval between the earliest start of the P wave and the bipolar atrial deflection, was measured both through the esophagus (PA-Eso) and the Hisian region (PA-His) (the latest depolarization of interatrial septum). The former was longer than the latter (P < 0.001) in 36 of 37 patients, showing that the esophagus recorded atrial signal, at the site of effective pacing, originates outside the interatrial septum. As the atrial depolarization recorded through the esophagus is significantly delayed compared with the Hisian region recording, a pure left origin of the esophageal signal can be hypothesized. This is supported by the well-known delayed depolarization, during sinus rhythm, of the left atrium posterior wall compared with the right atrium and interatrial septum. Measuring the interval between the standard ECG P wave and atrial depolarization recorded through esophagus in the site of effective pacing, provides a reliable noninvasive estimate of interatrial time conduction.

    Esophageal PP intervals for analysis of short-term heart rate variability in patients with atrioventricular block before and after insertion of a temporary ventricular inhibited pacemaker. Hsiao HC, Chiu HW, Lee SC, Kao T, Chang HY, Kong CW. Veterans Genl Hosp, Taiwan, ROC. Int J Cardiol 1998 May 15;64(3):271-6. Heart rate variability (HRV) analysis is a useful method for assessment of the activities of autonomic nervous system. The RR intervals in ECG is measured for this purpose. However, RR intervals are not suitable for HRV analysis in atrioventricular block (AV) block patients with ventricular inhibited (VVI) pacemaker, as the intervals will be fixed by the ventricular pacemaker. Thus we used an esophageal lead to detect PP intervals for analysis of HRV. The aim of this study was to evaluate the short-term HRV by using an esophageal electrode to detect the atrial signal and PP intervals in AV block patients. Fifteen AV block patients before and after temporary VVI pacemaker and 15 subjects with normal AV conduction (control group) were enrolled in this study. The atrial signals from esophageal lead, ECG and intraatrial lead were recorded. The duration was 10 min. We compared correlation coefficient of PP intervals from different leads in AV block patients and the control group. We also compared the PP interval's variability parameters between the control group and AV block patients, before and after insertion of a temporary ventricular inhibited pacemaker. The esophageal PP intervals were excellently correlated with intraatrial AA intervals (r=0.98+/-0.01). The HRV using esophageal PP intervals with time domain demonstrated a significant decrease in patients with AV block (standard deviation of all PP intervals (SDNN) (s)=0.022+/-0.014; percentage difference between adjacent PP intervals that are greater than 50 ms (pNN-50) (%)=0.052+/-0.038; square root of the mean of squares of differences between duration of neighboring PP intervals (r-MSDD) (s)=0.322+/-0.082) but this returned to normal after insertion of a temporary ventricular inhibited pacemaker (SDNN (s)=0.035+/-0.009; pNN-50 (%)=2.540+/-1.682; r-MSDD (s)=0.542+/-0.190). However, the ratio of low frequency/high frequency (LF/HF) still increased (LF/HF=4.120+/-1.802). The result of this short-term HRV analysis suggested that withdrawal of vagal tone or increased sympathetic activity in AV block patients compared with the control group. This appearance was normalized after insertion of a temporary VVI pacemaker. however, abnormal sympathovagal balance still remained.

    Heart rate variability in patients with atrioventricular block. Hsiao HC, Chiu HW, Lee SC, Kao T, Chang HY, Kong CW.Veterans Genl Hosp-Taipei. Chung Hua I Hsueh Tsa Chih (Taipei) 1997 Aug;60(2):81-5. BACKGROUND: Heart rate variability (HRV) analysis has been an established method for assessment of the activities of autonomic nervous system. Conventionally, the RR intervals from the surface electrocardiogram (ECG) are used for HRV analysis, however, analysis of the RR intervals may not be suitable in patients with atrioventricular (AV) node dysfunction, particularly in patients with certain degree of AV block. We used an esophageal electrode to detect PP intervals for HRV analysis in these patients. METHODS: Seven AV block patients and 13 subjects with normal AV conduction (control group) were enrolled in this study. The signals from esophageal lead, surface lead and intraatrial lead were recorded. Correlation coefficient of heart beat intervals from different leads was analyzed. Then we compared the HRV parameter recorded by esophageal lead between AV block patients and the control group. RESULTS: The AA intervals in intraatrial ECG and the PP intervals in surface ECG were poorly correlated (r = 0.489) in the AV block patients. However, intraatrial ECG was correlated well with esophageal ECG (r = 0.968). HRV with time domain decreased significantly in patients with AV block. The standard deviation of NN intervals (SDNN), pNN-50 and r-MSSD in the control group and the AV block patients were 0.035 +/- 0.006 vs. 0.021 +/- 0.016 seconds (p = 0.002), 3.210 +/- 3.120 vs. 0.050 +/- 0.040% (p = 0.027) and 0.577 +/- 0.181 vs. 0.318 +/- 0.084 seconds (p = 0.009), respectively. CONCLUSIONS: The esophageal lead recording is a non-invasive, easy and safe method to detect HRV of AV block patients whose vagal activity is abnormal. 

    Heart Rate Variability. Malik M, Camm AJ. St. George's Hosp Med School, London. Clin Cardiol 13, 570-576, 1990. Reduced heart rate variability carries an adverse prognosis in patients who have survived an acute myocardial infarction. This article reviews the physiology, technical problems of assessment, and clinical relevance of heart variability. The sympathovagal influence and the clinical assessment of heart rate variability are discussed. Methods measuring heart rate variability are classified into four groups, and the advantages and disadvantages of each group are described. Concentration is on risk stratification of postmyocardial infarction patients. The evidence suggests that heart rate variability is the single most important predictor of those patients who are at high risk of sudden death or serious ventricular arrhythmias.Back

    Atrial late potentials in patients with paroxysmal atrial fibrillation detected using a high gain, signal-averaged esophageal lead. Villani GQ, Piepoli M, Cripps T, Rosi A, Gazzola U. General Hospital, Piacenza, Italy. Pacing Clin Electrophysiol 1994 17(6):1118-23.  High gain, signal-averaged ECGs using conventional surface lead technique and a transesophageal lead technique were performed in 45 idiopathic paroxysmal atrial fibrillation patients and in 33 normal controls. Both techniques showed increased P wave duration in patients compared with the controls (P < 0.001), but higher P wave amplitudes were obtained using the transesophageal technique compared with surface leads (patients: 169.8 +/- 81.7 microV vs 15.8 +/- 7.3 microV; P < 0.0005; controls: 163.5 +/- 22.1 microV vs 18.5 +/- 5.2 microV; P < 0.0005). The signal-averaged transesophageal lead, but not the surface recordings, identified the presence of atrial late potentials evidenced by lower root mean square voltages in the terminal portion of the P wave: in last 10 seconds, 4.4 +/- 1.3 microV versus 8.5 +/- 3.0 microV; P < 0.001; in last 20 seconds, 7.0 +/- 2.3 microV versus 16.0 +/- 7.9 microV; P < 0.001; in last 30 seconds, 12.5 +/- 5.3 microV versus 23.8 +/- 12.8 microV; P < 0.001, in patients with respect to controls. The criterion P wave duration > or = 110 msec had 85% sensitivity, 100% specificity, and 100% positive predictive value in identifying the patients; the combined criteria P wave duration > or = 110 msec and root mean square for the last 10 msec < or = 6.5 showed 80% sensitivity, 100% specificity, and 100% predictive value. The signal-averaged transesophageal lead produces a higher amplitude signal, which reveals fractionation of atrial activation in atrial fibrillation and allows identification of individuals predisposed to this arrhythmia.

    Wave recognition and use of the intraoperative unipolar esophageal electrocardiogram. Jain U. University of California at San Francisco.J Clin Anesth 1997 Sep;9(6):487-92. STUDY OBJECTIVES: To evaluate the automated determination of onset and offset times and amplitudes of all the PQRST waves from simultaneously recorded surface electrocardiogram (SECG) and unipolar esophageal ECG (EsECG). The occurrence of ST segment deviation is also examined. DESIGN: Prospective, observational study. SETTING: University hospital. PATIENTS: 30 patients undergoing coronary artery bypass graft (CABG) surgery. INTERVENTIONS: SECG and two-lead unipolar EsECG were recorded after induction of anesthesia and before cardiopulmonary bypass (CPB). MEASUREMENTS AND MAIN RESULTS: The amplitudes of the P and T waves and the ST segment deviation were measured. EsECG had more noise than SECG. Slight movement of the esophageal electrodes occasionally caused substantial changes in the wave amplitudes and ST segment deviation in the unipolar EsECG. The maximum P wave amplitude in EsECG was, on average, 97% greater than the maximum P wave amplitude in SECG, ST segment deviation in EsECG was observed in the absence of ST segment deviation in SECG and vice versa. CONCLUSIONS: The recognition and measurement of all the PQRST waves can be improved and automated by simultaneous use of EsECG and SECG. The P wave amplitude is greater in EsECG than in SECG, which may faciliate the identification of supraventricular versus ventricular arrhythmias. ST segment deviation in the unipolar EsECG may not be suitable for the routine detection of ischemia.

    A noninvasive pre-atrial activity recording by signal averaging using esophageal electrode. Kao T, Yu BC, Kong CW, Chen CY, Chiang BN. Institute of Medical Engineering, Yang-ming Medical College, Taipei. Pacing Clin Electrophysiol 1988;11(8):1168-75. A noninvasive method employing the technique of signal averaging has been developed for recording sinoatrial (S-A) activity (pre-P wave). Recordings were obtained in man at the time of right heart catheterization. A bipolar esophageal electrode was utilized to record the prominent P waves that were used for triggering in the averaging process. After summing 150 beats, which had coefficients of correlation 0.97 or larger, deflections of small amplitude (less than 40 microV) were obtained preceding the atrial activity. Direct catheter recordings were also taken for comparison. With the new noninvasive method, the sinoatrial conduction time (SACT) estimated for patients with sick sinus syndrome (SSS) was 106 +/- 24 ms (101 +/- 20 ms for the same group measured directly). The SACT for healthy subjects used as the control group was 55 +/- 18 ms. There was good correlation between the pre-atrial activity recorded noninvasively by the esophageal electrode method and invasively from the direct catheter method. The linear correlation coefficient between these two techniques was 0.89 (P less than 0.001) in 17 patients.

    Heart rate variability. Is it influenced by disturbed sinoatrial node function? Sosnowski M, Petelenz T. Silesian Heart Center, Katowice, Poland. J Electrocardiol 1995 Jul;28(3):245-51. Analysis of heart rate variability (HRV) is commonly used to assess the influences of the autonomic nervous system on the heart; however, its relation to the sinoatrial node function has not been clearly defined. In this study, the authors performed HRV investigations in 150 patients (51 women and 99 men; mean age, 49 years; range, 17-80 years) in whom clinical observation and electrophysiologic transesophageal studies proved sinoatrial node dysfunction (SAND) and in 50 healthy control subjects (19 women and 31 men; mean age, 37 years; range, 15-60 years). All examined subjects underwent transesophageal left atrial overdrive pacing for the evaluation of sinus node recovery. The HRV analysis was based on 1-minute esophageal electrocardiographic recordings. Two time-domain HRV variables were measured: variability range ([VR]) the difference between the longest and the shortest sinus cycle length, divided by basic sinus cycle length) and beat-to-beat variability ([DSCL]--the maximum difference between any two consecutive sinus cycle lengths) during a 1-minute recording. Because of the known effects of age and basic sinus cycle, statistically adjusted means of VR and DSCL were compared. In patients suffering from SAND, DSCL was significantly higher than in the control subjects (198 +/- 206 vs 98 +/- 89 ms, respectively), as was VR (30.3 +/- 23.3% vs 20.9 +/- 121.1%).

    Evaluation of rate-responsive pacemakers by transesophageal Holter monitoring of spontaneous atrial rate. Bongiorni MG, Soldati E, Paperini L, Pozzolini A, Levorato D, Arena G, Pistelli P, Quirino G, Biagini A, Contini C. CNR, Institute of Clinical Physiology, Pisa, Italy. Pacing Clin Electrophysiol 1990 Dec;13(12 Pt 2):1755-60. One of the most important problems in rate responsive (RR) pacing is the clinical experimental evaluation of the reliability of various sensors. In particular, it is difficult to test their sensitivity and specificity during daily activity of the patients. Atrial rate, when present and normal, is the most physiological marker of metabolic requirements, but sometimes it is impossible to analyze the P wave in ventricular paced rhythm during routinely performed tests (e.g., ergometric test and 24-hour Holter monitoring). During various physical activities, we monitored atrial electrograms on an esophageal lead on the first channel of a standard Holter tape recorder; on the second channel a surface ECG lead was recorded. We selected 10 patients with high grade heart block and normal sinus node function paced in RR-VVI mode. RR pacing was obtained using various sensors (body activity, blood temperature, spike-T interval, minute ventilation). The good quality of recording allowed an easy evaluation of atrial and ventricular rates. In four cases an appropriate increase in heart rate was documented; sensitivity threshold and/or rate response slope were reprogrammed when indicated. The pacing rate of one patient did not parallel the atrial rate during walking only. In three cases, we observed a delay in the ventricular rate increase, with ventricular rate decreasing at peak exercise despite further atrial rate increase. In the last two patients, we observed inappropriate pacing response; pacing rate increased later and to a lower level than the atrial one. This new method is applied easily and appears reliable to evaluate the response of RR pacemakers to individual metabolic needs.

    Telemetric monitoring of esophageal ECG. Bagger H. Ugeskr Laeger 1991 Nov 18;153(47):3321-2   Recording of the esophageal ECG is important in differentiating between different types of tachycardia. A method is described by which the (CardioCommand) pill electrode can be re-used. The electrode is introduced through the nose and connected to a telemetric monitor. In this way the esophageal ECG can be monitored continuously in order to characterize transient, self-limiting tachycardias. Monitoring has been performed for up to four days without problems.

    Recording the bundle of His potential using an esophageal electrode. Lukoshiavichiute AI, Grutsite VR, Kasparavichius IIa. Kardiologiia 1986 Jun;26(6):34-8. A noninvasive method for recording His bundle potential is reported that includes amplification of ECG in bipolar esophagosternal leads. A total of 106 patients were examined, with the His potential recorded in 78 (73.6%) of those. The method was validated by simultaneously recorded intracardiac electrograms in 6 patients and by atrial pacing in 3 patients. The advantages and limitations of this method are discussed.

    Lead configurations in esophageal electrocardiography. Jadvar H, Jenkins JM. Med Instrum 1987 Jun;21(3):158-65. (Published erratum appears in Med Instrum 1987 Aug;21(4):243.) There are many clinical situations that present the need for special purpose electrocardiography using standard equipment. These include monitoring cardiac activity from temporary myocardial leads implanted following cardiac surgery, detecting signals from intracardiac catheter leads, and noninvasive atrial recording from the esophagus. It is often difficult to connect nonstandard leads and access the individual amplifiers. In this article, we present the case for an esophageal electrode such as the Pill Electrode (CardioCommand). We describe several configurations for connecting this electrode to electrocardiographs and comment on the merits and shortcomings of each method.

    Bipolar esophageal electrocardiography by using standard limb leads. Liu X, Lu Z, Zhao H, Zhang C, Cai L.Tongji Medical University, Wuhan. J Tongji Med Univ 1997;17(1):32-5. The ear-xiphisternum distance (EXD, the distance from the low edge of the ear to the xiphisternal basis in supine position) was used as a reference value for esophageal catheter insertion. ECGs recorded in the esophagus with bipolar electrocardiography using standard limb lead (ESLL) and conventional unipolar lead (ECUL) were compared. 112 patients with sinus rhythm and 76 patients during paroxysmal supraventricular tachycardia (PSVT) whose P-wave and QRS complex did not overlap were studied. The results suggested that in sinus rhythm the amplitude of the P-wave in ESLL was larger and the T-wave was smaller than in ECUL. During PSVT, the P-wave was much clear and higher in each lead of ESLL than that in ECUL. The ideal range of esophageal ECG recording was situated between the end of EXD and 6.5 cm proximal to it.

    Activation sequence of the left atrium studied by esophageal leads. Deng ZW, Huang ZZ, Liang YR. Chung Hua Hsin Hsueh Kuan Ping Tsa Chih 1989;17(1):23-5. The intracardiac electrogram recorded in upper, middle and lower right atrium showed a positive, biphasic and negative P wave, respectively. This concept has been widely used in positioning the electrode in transesophageal atrial pacing (TEAP). However, in examination of the P wave figure in the unipolar lead along the esophagus by each two cm distance in 100 normal adults, we found that 32 subjects did not fulfill the above-mentioned criteria partially or completely. In order to study the underlying mechanism of such phenomenon, 190 patients undergone TEAP were examined by simultaneous recording of 2 unipolar esophageal leads (interelectrode distance 2-3 cm) with surface ECG. The patients were classified into 3 groups according to the morphology relation between the upper and lower esophageal P waves: Group A consisting of 155 cases (81.6%) in which the fashion of P wave changes was consistent with the usual criteria; Group B 17 cases (8.9%) was not consistent with the criteria; Group C 18 cases (9.5%) was in a reversed manner. The PEP-PED interval (measured from the peak of P wave in proximal esophageal lead to that in distal esophageal lead) was used as an indicator of left atrium activation sequence in vertical direction. Its value in these three groups was 6.3 +/- 10.1, -6.8 +/- 6.9 and -15.7 +/- 7.3 ms, respectively (P < 0.001), suggesting in the latter two groups the left atrium activation was directed upward.

    Primary studies on transesophageal atrial activation mapping. Deng ZW. Chung Hua I Hsueh Tsa Chih 1989 Feb;69(2):66-8. A method of transesophageal atrial activation sequence determination was created by using simultaneous recording with two unipolar esophageal leads and V1, as well as by the bipolar esophageal lead. Based on the assumption that the peak of P wave in the uni-polar esophageal lead (PE) reflects roughly the activation time of the left posterior atrium wall, and so as to the peak of P wave in V1 (PV1) for the right anterior atrium wall, four items were used as indicators of atrial activation sequence: 1. PV1-PE interval; 2. PEp-PED interval (measured from the peak of P wave in the proximal to that in the distal esophageal lead); 3. Morphology of the bipolar esophageal P wave (PEB); 4. PEp-PED-PV1 sequence; In 190 cases having undergone transesophageal atrial pacing with sinus rhythm, PV1-PE measurement was 28.0 +/- 13.9 ms and PEp-PED was 3 +/- 12 ms. During atrioventricular reciprocating tachycardia in 17 cases with type-A preexcitation and 18 cases with left-sided concealed accessory pathway, PV1-PE was -63.3 +/- 19.0 and -63.7 +/- 27.5 ms, with PEp-PED -17.1 +/- 22.0 and 16.4 +/- 16.7 ms respectively. Transesophageal atrial activation sequence determination is helpful in raising the diagnostic accuracy for arrhythmia.

    Simplified esophageal electrocardiography using bipolar recording leads. Hammill SC, Pritchett EL. Ann Intern Med 1981 Jul;95(1):14-8. Diagnosing cardiac arrhythmias is easier if the P wave can be identified clearly. Esophageal electrocardiography with a unipolar recording lead attached to the V1 terminal of an ECG machine has been used in the past to show P waves. We used both bipolar and unipolar recording leads and standard ECG equipment to record the esophageal ECG and then compared the results obtained with both leads. Twenty-two cardiac rhythms were evaluated in 15 patients. The unipolar lead recorded a P wave that was smaller than the QRS complex (0.83 +/- 0.47 mV and 1.28 +/- 0.79 mV, respectively, p less than 0.01) and was obscured when the two depolarizations were nearly simultaneous. The bipolar lead recorded a P wave that was larger than the QRS complex (0.93 +/- 0.62 mV and 0.33 +/- 0.3 mV, respectively, p < 0.001) and was never obscured. The unipolar lead recorded a P-to-QRS ratio that was smaller than that recorded by the bipolar lead (0.8 +/- 0.5 and 3.3 +/- 1.8, respectively, p < 0.001). A bipolar esophageal lead can be recorded simply at the bedside using a standard ECG machine and is superior to the conventional unipolar lead.

    Limitations of esophageal electrocardiography in recording atrial rhythms after orthotopic heart transplantation. Ellenbogen KA, Arrowood JA, Cohen MD, Szentpetery S. McGuire VA Med Ctr, Richmond. J Heart Transplant 1987;6(3):167-70. Esophageal electrocardiography is a commonly used tool for the differential diagnosis of arrhythmias. A 39-year-old man who underwent orthotopic heart transplantation developed a narrow complex tachycardia. Esophageal electrocardiography showed a junctional tachycardia (recording native atrial activity alone), whereas atrial intracavitary electrograms showed the correct diagnosis of atrial flutter. Esophageal recording in patients who undergo orthotopic heart transplantation is a useful technique for recording native atrial activity. For arrhythmia diagnosis in these patients it is frequently necessary to record donor atrial activity with intracavitary electrograms. The limitations of esophageal electrocardiography should be recognized by physicians who care for these patients.

    Problems in the diagnosis and clinical assessment of atrial dissociation. Snezhitskii VA, Volkov VN, Radevich PA, Simonenko IA, Kul'sha LK, Madekina GA. Ter Arkh 1995;67(9):73-5. At registration of ECG esophageal leads in two patients with ischemic heart disease an extra atrial rhythm was recorded missed by standard ECG. Similar cases from the literature are considered.

    Intraoperative esophageal electrocardiography for dysrhythmia analysis and therapy in pediatric cardiac surgical patients.Greeley WJ, Kates RA, Bushman GA, Armstrong BE, Grant JW. Anesthesiology 1986 Dec;65(6):669-72.

    Intraoperative esophageal electrocardiography. Kates RA.Mt Sinai J Med 1984 Sep;51(5):573-7.

    Another solution to monitoring the electrocardiograph in patients with extensive burn injury [letter]  Roth JV   Anesthesiology (United States), May 1998, 88(5) p1416.

    Evaluation of extrasystoles by esophageal electrocardiography. Hardebeck CJ. Am J Cardiol 1987 May 1;59(12):1230.

    A method of esophageal electrogram recording for diagnostic atrial and ventricular pacing. Prochaczek F, Jerzy G, Stopczyk MJ. Pacing Clin Electrophysiol 1990 Sep;13(9):1136-41. Silesian Medical Academy, Poland. This study evaluates improvement of the electrogram sensed via an esophageal catheter with the sensing electrode adjacent to the stimulating electrode with and without a specialized artifact suppression system. In 100 patients (65 men and 35 women) aged 16-60 years (mean 48 years), esophageal recordings of left atrial activity were obtained during simultaneous transesophageal atrial pacing. Transesophageal ventricular pacing was performed in an additional 34 patients. Without the suppression system, ventricular paced activity, recorded from the esophagus, was not suitable for interpretation. About 10% of the atrial electrogram response could be recorded and evaluated during atrial pacing. With the stimulus artifact suppression system, interpretable recordings were obtained 100% of the time during atrial and ventricular recordings. The method described allows use of transesophageal diagnostic testing where previously only the intracardiac route was possible.