Hypertrophic cardiomyopathy: the importance of arrhythmic events in patients at risk for sudden cardiac death.

Objective: To evaluate, in patients with hypertrophic cardiomyopathy and risk for SCD who underwent implantable cardioverter-defibrillator (ICD) implantation: a- the occurrence of arrhythmic events; b- the occurrence of clinical events and their correlation with arrhythmic events; c- the occurrence of ICD shock therapy and clinical and functional correlations; d- clinical and functional predictors of prognosis.

Methods: Twenty six patients with hypertrophic cardiomyopathy and risk factors for SCD undergoing ICD implantation from May, 2000 to January, 2004 (mean follow-up = 20 months) were studied. Fourteen patients (53.8%) were females and the mean age was 42.7 years. ICD was indicated for primary prevention of sudden cardiac death in 16 patients (61.5%), and for secondary prevention in 10 patients (38.5%). Twenty patients (76.9%) presented syncope prior to ICD implantation; half of them were related to ventricular fibrillation or sustained ventricular tachycardia, 15 (57.7%) had a history of familial sudden death, 12 patients (46.2%) had nonsustained ventricular tachycardia on the 24-hour Holter monitoring, and five (19.2%) had an interventricular septal thickness greater than 30 mm.

Results: Four shock therapies were recorded by the ICD in potentially lethal arrhythmias (three patients with sustained ventricular tachycardia and one patient with ventricular fibrillation) during the follow-up. One death occurred, probably due to a thromboembolic stroke. Four patients had recurrence of syncope with no arrhythmic event recorded by the ICD. The statistical analysis showed a significant difference in early ICD shock therapy in patients whose interventricular septal thickness was greater than 30 mm.

Conclusion: 1- occurrence of arrhythmic events in 50% of the patients; most of them (62%) were ventricular tachycardia, whether sustained (31%) or nonsustained (31%); in the remaining patients paroxysmal supraventricular tachycardia was observed. 2- recurrent syncope in the minority of the patients (16%), however not associated with the presence of arrhythmic events. 3- the presence of an interventricular septal thickness greater than 30 mm in the echocardiogram was associated with early shock therapy (p = 0.003). 4- absence of clinical or functional predictors.