[Frequent arrhythmias in Wolff-Parkinson-White syndrome]

The real knowledge of the natural history in preexcitation syndrome is not possible, Circus movement reciprocal atrioventricular tachycardia is seen en 60% of the patients. Mostly of them are orthodromic. In this group, A-H increases in duration. H-V become normal and the delta wave disappears in the electrophysiologic study during the tachycardia. In the antidromic group, A-delta decreases and H deflexion cannot be recognized. Pre-excitation with atrial flutter is a rare but very dangerous situation when atrial impulses are conducted by the anomalous bundle, because the very high ventricular rate with 250 mseg R-R intervals. The same happens in patients with atrial fibrillation, observed in 5% of the patients with WPW syndrome; this arrhythmia may provoke multiform ventricular tachycardia, ventricular fibrillation and sudden death. Sudden death occurs in 0.1% of asymptomatic patients with WPW in 1% in those with reciprocal tachycardias and in 5.6% of the patients with atrial fibrillation and R-R intervals of 250 mseg of less.