Lack of prognostic value of syncope in patients with Wolff-Parkinson-White syndrome Syncope in patients with Wolff-Parkinson-White syndrome may be considered a premonitory event heralding the future development of sudden death. Therefore, the clinical and electrophysiologic data of 101 patients with Wolff-Parkinson-White syndrome referred for invasive evaluation of known arrhythmias were reviewed to assess the incidence and clinical relevance of syncope. Thirty-six patients reported the occurrence of one or more syncopal episodes (group 1) and 65 patients had no syncope (group 2). These two groups did not differ significantly with regard to age, gender, incidence and characteristics of arrhythmia, clinical history, frequency of arrhythmic events and presence of associated cardiac disease. There were 10 patients in group 1 and 12 in group 2 who had ventricular fibrillation. There were no statistical differences between the two groups with respect to the effective refractory period of the right atrium, atrioventricular node, accessory pathway and right ventricle. Furthermore, no differences between the two groups were noted with respect to cycle length of circus movement tachycardia, mean heart rate during atrial fibrillation, and minimum RR interval during atrial fibrillation. In addition, the accessory pathway location was not significantly different between group 1 and group 2. The occurrence of syncope could not be predicted from any electrophysiologic finding and this symptom had a low sensitivity and specificity for recognition of dangerous rapid heart rates. Furthermore, the prognostic value of syncope was less accurate and predictive than the shortest RR interval during atrial fibrillation and the anterograde effective refractory period of the accessory pathway for aborted sudden death occurrence. 