Ventricular fibrillation induced by rapid atrial rates in patients with hypertrophic cardiomyopathy

Aims To describe the mechanisms of induction of ventricular fibrillation (V F) by rapid atrial rates in patients with hypertrophic cardiomyopathy (HCM) . Methods Electrophysiological studies, management and follow-up in three pat ients with HCM with VF induced by atrial pacing. Results In one patient, spontaneous sinus tachycardia triggered VF. In anot her patient. VF occurred after verapamil infusion during rapid atrial fibri llation, and in the remaining patient there was no clinical VF. In all thre e patients, short runs of atrial pacing (cycle length 272-380 ms) induced V F, and QRS widening preceded fibrillation in all patients. Marked ventricul ar electrogram fragmentation was documented in one patient during atrial pa cing and in another patient during late ventricular extrastimuli. Hypotensi on was associated with sinus tachycardia in one patient. The two patients d eveloping clinical VF underwent atrioventricular (AV) junctional ablation; a ventricular defibrillator was implanted in one, and a mode-switching dual -chamber pacemaker in the other. No arrhythmic events occurred during 34- a nd 35-month follow-up, respectively. In the other patient, postatrial fibri llation pauses caused syncope, and he is asymptomatic 52 months after impla ntation of a dual-chamber pacemaker. Conclusions Rapid atrial rates can trigger VF in some patients with HCM, pr obably through a combination of electrophysiological and ischaemic mechanis ms. AV junctional ablation may prevent VF in selected cases. (Europace 2000 ; 2: 327-332) (C) 2000 The European Society of Cardiology.