The electrocardiogram in patients with multiple accessory atrioventricular pathways.

The 12 lead electrocardiographic (ECG) findings were reviewed in 17 patients having two or more accessory pathways as documented during electrophysiologic study in all 17 patients and by intraoperative mapping in 8. Twelve patients had findings suggesting the presence of more than one atrioventricular (AV) pathway. These were 1) more than one P wave configuration during orthodromic circus movement tachycardia (four patients); 2) a "mismatch" between the location of the ventricular and atrial ends of the accessory pathway as assessed when comparing exclusive AV and ventriculoatrial conduction over the accessory pathway during antidromic and orthodromic circus movement tachycardia, respectively (seven patients); 3) atrial fibrillation showing more than one pre-excitation pattern (six patients); 4) a spontaneous change from orthodromic to antidromic circus movement tachycardia and vice versa (two patients); 5) a spontaneous change from one type of antidromic tachycardia to another (two patients); and 6) a change in pre-excitation pattern after administration of a drug that prolongs the anterograde refractory period of the accessory pathway (three patients). The retrospective nature of this study does not allow conclusions as to the true value of the ECG in predicting the presence of more than one accessory pathway. This issue needs to be evaluated in a prospective study.