[Mitral valve prolapse. Results of electrophysiological studies].

Classically, the frequency of latent left-sided Kent bundles and ventricular tachycardia (VT) is increased in mitral valve prolapse (MVP). To verify this hypothesis, 23 patients with clinical and echocardiographic (M mode and 2D) signs of MVP underwent electrophysiological studies for dizziness or syncope (12 cases) or palpitations (11 cases). In addition to the standard electrophysiological studies, analysis of sinoatrial and atrioventricular conduction, they underwent programmed ventricular pacing (St V2): coupled and then paired St V2 in sinus rhythm and during ventricular pacing (100-150/min) under basal conditions (15 patients), after injection of 2 mg Atropine (6 patients), and 10 micrograms of Isoproterenol (4 patients). These manoeuvres showed that symptoms of dizziness were due to increased vagal tone in 6 cases (associated with paroxysmal nodal tachycardia--PNT--in 3 cases), to sinoatrial block in 2 cases (associated with atrial tachycardia in 1 case), to suprahisian conduction defects in 3 cases (associated with atrial tachycardia in 1 case) and to VT in 1 case. Palpitations were due to VT in 1 case, atrial tachycardia in 1 case and PNT in 9 cases. Our analysis showed a high incidence of PNT (10 cases) with normal inter critical ECG. These arrhythmias were due to intranodal reentry in 7 cases (70%), to a latent left-sided Kent bundle in 2 cases and to a paraseptal Kent bundle in 1 case. These PNT were characterised by induction during exercise (6 cases) and by their association with flutter-type reentry (5 cases).(ABSTRACT TRUNCATED AT 250 WORDS)