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%).