Biffi A, Ammirati F, Caselli G, Fernando F, Cardinale M, Faletra E, Mazzuca V, Verdile L, Santini M. Sports Science Institute-Italian Olympic Committee, Rome. Am J Cardiol 1993 Oct 15;72(12):922-6. The aim of this study was to verify the use of transesophageal atrial pacing in reproducing tachyarrhythmias in 22 top-level athletes symptomatic for palpitations, with no evidence of arrhythmias or cardiac anomalies by the standard noninvasive diagnostic techniques. The transesophageal stimulation protocol was divided in 2 sections: at rest and during exercise on the bicycle ergometer in the upright position. Although transesophageal pacing at rest did not induce any arrhythmias in 18 of 22 athletes, during exercise it induced tachyarrhythmias. This occurred in all 16 athletes who had palpitations during physical activity. Electrophysiologic characteristics of induced atrial tachyarrhythmia suggested reentry within the atrioventricular node in 9 of 18 athletes: atrial fibrillation in 5, atrial flutter in 2, orthodromic reciprocating tachycardia due to concealed anomalous pathway in 1, and automatic atrial tachycardia in 1. This study stresses the clinical importance of palpitations during physical exercise and shows that transesophageal pacing performed during exercise is an important diagnostic tool in reproducing the previously described symptoms and in detecting the underlying tachyarrhythmias.