Ambulatory monitoring of the sudden death of an adolescent with hypertrophic cardiomyopathy.

Sudden death is an important cause of mortality in hypertrophic cardiomyopathy. Several mechanisms have been proposed, but ambulatory monitoring of the event has rarely occurred. The case of an adolescent girl with congenital hypertrophic cardiomyopathy and arthrogryposis multiplex congenita is presented. Despite appropriate therapy and severe activity limitation, the patient's condition progressively worsened. The patient died suddenly in her sleep, one month after a myocardial myomectomy for subaortic stenosis. The fortuitous ambulatory electrocardiographic (ECG) monitoring of the event recorded polymorphic ventricular tachycardia degrading into ventricular fibrillation. Retrospective review of previous ambulatory ECG revealed the presence of nonsustained ventricular tachycardia, a predictive determinant for sudden death, and atrioventricular node dysfunction. However, the patient had never reported symptoms during the dysrhythmias. The pathological specimen showed an unexpected old apical infarction scar, suggesting that her preoperative cardiac status was worse than suspected. In summary, the mechanism of sudden death in this patient was revealed by ambulatory ECG monitoring, and the involvement of neural and myocardial factors are proposed.