[The excitation-conduction system of the heart in primary mitral valve prolapse (electrophysiological study)].

Forty patients (mean age 40 yrs) with primary mitral valve prolapse (MVP) and 20 healthy controls were subjected to electrophysiologic investigation. The following measurements were performed: 1) intracardiac conduction time, 2) effective and functional refractory periods of the right atrium, a-v node and right ventricle, 3) Wenkebach point, 4) retrograde Wenkebach point. Disturbances of intracardiac conduction were detected in 13 (32.5%) patients with MVP (in 8 patients within proximal part of the conduction system, in 5 patients distally). Patients with MVP were more sensitive to ajmaline. Conduction time in the proximal part was significantly increased only in these patients. The incidence of retrograde conduction was more frequent in the patients with MVP than in the controls. In 12 (30%) patients with MVP, constant conduction time and high value of retrograde Wenkebach point were found. Mean values of effective and functional refractory periods of the right ventricle and effective refractory period of the a-v node were not significantly different in both groups. In patients with MVP, mean values of effective and functional refractory periods of the right atrium were significantly lower and functional refractory period of the a-v node significantly higher than in the controls. In 8 (20%) patients with MVP and in 2 (10%) controls, longitudinal division of the a-v node was found. Atrial hyperreactivity was detected in 14 (35%) patients and in 3 (15%) controls. In conclusion, MVP is often accompanied by electrophysiologic abnormalities, such as disturbed intracardiac conduction, retrograde preexcitation, shortening of atrial refractory periods, longitudinal division of the a-v node and atrial hyperreactivity.