Vergara G, Furlanello F, Disertori M, Inama G, Guarnerio M, Bettini R, Cozzi F. Division of Cardiology and Arrhythmologic Centre, S. Chiara Hospital, Trento, Italy. Eur Heart J 1988 Oct;9(10):1119-25. Even today there is controversy as regards the best approach to asymptomatic or slightly symptomatic athletes with the WPW syndrome as regards fitness for sports activity, especially in some countries where the doctor is responsible for certifying sports fitness. This study concerns 84 asymptomatic or slightly symptomatic athletes (66 males, 18 females, mean age 21.7 years, range 12-44 years) who underwent a stimulation protocol the end-point of which was the induction of atrial fibrillation (or, if not possible, atrial tachyarrhythmia) in the basal state and during bicycle stress test with transesophageal atrial pacing. The 81 athletes in whom the end-point was reached were divided into two groups: Group I includes the 32 athletes with the shortest R-R interval between pre-excited beats less than or equal to 240 ms in the basal state and/or less than or equal to 210 ms during bicycle ergometer test, Group II includes the other 49 patients. The evaluation during exercise was not carried out in four athletes because of serious haemodynamic compromise due to the arrhythmia induced in the basal state. Only 21/32 athletes would have been included in Group I if only evaluated in the basal state. In 30/81 athletes (37%), there was discrepancy between the result of stimulation and the result of the usual non-invasive evaluation (Holter monitoring, ergometric stress test, ajmaline test). On average, 40 min are required for the performance of the study protocol except when the induced arrhythmia lasts more than 5 min.