[Paroxysmal atrial fibrillation: main cause of syncope in hypertrophic cardiomyopathy].

The aim of this retrospective study was to determine the mechanism of syncope in idiopathic hypertrophic cardiomyopathy (HCM). An electrocardiographic study was undertaken in 43 patients with HCM: 27 (Group I) had a history of syncope and 16 (Group II) had no history of syncope but were investigated for conduction defects (n = 7) or unsustained ventricular tachycardia (VT) (n = 9). The stimulation protocol used programmed atrial pacing with 1 and 2 extrastimuli and ventricular pacing using up to 3 extrastimuli delivered at 2 sites. The following results were obtained: sustained atrial fibrillation (AF) (> 1 min) was induced in 21 patients in Group I (78%), 4 in Group II (25%); VT was induced in 3 patients in Group I (11%), and 3 in Group II (19%); infra-Hisian block was detected in 1 patient in Group I. The mechanism of syncope was elucidated in 23 patients in Group I (85%): one atrioventricular block 1 sinus node dysfunction, 18 atrial fibrillations, 2 associations of AF-VT and 1 VT. The authors conclude that the prevalence of inducible AF was higher in patients with HCA and syncope than in controls and HCM without syncope: this was the only detectable difference in 67% of patients with unexplained syncope. Paroxysmal AF could therefore explain malaise or syncope in up to 2/3 of cases of HCM.