Long-term survival after cardiac arrest in hypertrophic cardiomyopathy

Patients with hypertrophic cardiomyopathy (HCM) and aborted cardiac arrest are generally regarded as a high-risk subgroup susceptible to future major cardiac events and an unfavorable prognosis. However, outcome over extended time periods after major arrhythmic events is unresolved in such HCM patients.

This study sought to more completely define the natural history of HCM.

Of 916 HCM patients in the Minneapolis Heart Institute registry, 39 experienced either cardiac arrest (n = 21) or an appropriate shock from a prophylactically implanted cardioverter-defibrillator (ICD) (n = 18), and were assessed prospectively.

Age at initial arrhythmic event was 34 +/- 17 years (range 8 to 68; 67% <40 years). Of the 39 study patients, 32 (82%) survived after their initial cardiac event (for 9.4 +/- 7.6 years; up to 30 years), including 14 patients for >or=10 years (36%) and 4 patients >or=20 years (10%). Of the 32 survivors, 15 (47%) have not experienced subsequent events, and 17 (53%) had >or=1 additional cardiac arrest or appropriate ICD intervention. Annual HCM-related mortality was 1.4%, similar to general HCM populations, and 88% of patients were free of HCM-related death over the follow-up period. Survival from potentially lethal arrhythmias was associated with no or only mild heart failure symptoms in 29 of 32 patients (91%) at most recent evaluation.

In HCM, long-term survival up to 30 years may follow cardiac arrest with or without ICD intervention. Disabling heart failure symptoms were uncommon after these arrhythmic events, at last follow-up. These novel observations regarding the natural history of HCM underscore the unpredictability of the arrhythmogenic substrate, which may remain dormant over extended periods of time.