[Mitral valve prolapse: do rhythm disorders have an electrophysiologic substratum?].
The mechanism of arrhythmias in mitral valve prolapse (MVP) is still unclear. The aim of this study was to determine if there were electrophysiological features common to patients with MVP. Eighteen patients with MVP documented on echo and angiocardiography underwent electrophysiological investigation. The series comprised 5 patients with ventricular arrhythmias and 5 with supraventricular arrhythmias, two of whom had ECG appearances of the Wolff-Parkinson-White, syndrome, and one a short PR interval. The RR interval, PR interval, intraatrial conduction (PA), atrio-hisian conduction (AH), intraventricular conduction (HV) the effective refractory periods of the atrium, AV node and ventricle, and the corrected sinus node recovery time were measured in the MVP group and in 20 presumed normal control subjects. There was a significant increase in the PR interval (p less than 0,05) at the expense of nodal conduction (AH) in the MVP group. In addition the Wenckebach point was significantly lower in this group. The other electrophysiological parameters in spontaneous rhythm and the atrial, AV nodal and ventricular refractory periods were the same in both groups. Sinus node function was comparable in both groups. In two patients without paiviously documented tachycardia, junctional tachycardia was initiated by provocative stimulation. However, no ventricular arrhythmias could be induced by pacing. A large number of preexcitation syndromes was observed in the MVP group (4/18), including one case of a latent Kent bundle, in patients with paroxysmal supraventricular tachycardias. On the other hand, the value of electrophysiological investigation seems to be limited for clarifying the mechanisms of the ventricular arrhythmias, probably because of their endomyocardial origin. Nevertheless, hemodynamic investigation showed abnormalities of left ventricular contraction in 4 of the 5 patients with ventricular arrhythmias.