Latent sinoatrial conduction disturbances in symptomatic patients with Wolff-Parkinson-White syndrome.

Sinoatrial conduction abnormalities were studied in fourteen patients with Wolff-Parkinson-White (WPW) syndrome and frequent attacks of supraventricular paroxysmal tachycardia. Sinoatrial conduction time (SACT), obtained by the method of constant atrial pacing, was prolonged in all but two patients. The mean value was 277 +/- 56 ms (mean +/- SD). SACT was measured in the same way in sixteen patients without signs of pre-excitation or sinoatrial disease; SACT was significantly shorter (p less than 0.001) than in the WPW group of patients. The prolongation of SACT in patients with WPW syndrome was confirmed by measuring SACT by the alternative method of programmed atrial stimulation. SACT was found to be prolonged in eight patients (mean +/- SD = 239 +/- 47 ms). Whether our results should be attributed to WPW syndrome or frequent supraventricular tachycardias--both being a characteristic feature of our patients--remains uncertain. The results of this study, however, indicate that in symptomatic patients with WPW syndrome and frequent episodes of supraventricular tachycardia, sinoatrial conduction is frequently impaired. Slackening of the sinoatrial conduction is a possible predisposing factor for initiation of tachycardias in the WPW syndrome.