The Natural History of Nonobstructive Hypertrophic Cardiomyopathy.

OBJECTIVE:To describe the survival of a large nonobstructive hypertrophic cardiomyopathy (NO-HCM) cohort and to identify risk factors for increased mortality in this population. PATIENTS AND METHODS:Patients were identified from the Mayo Clinic HCM database from January 1, 1975, through November 30, 2006, for this retrospective observational study. Patients with resting or provocable left ventricular outflow tract gradients were excluded. Echocardiographic, clinical, and genetic data were compared between subgroups, and survival data were compared with expected population rates. RESULTS:A total of 706 patients with NO-HCM were identified. During median follow-up of 5 years (mean, 7 years), there were 208 deaths. Overall survival was no different than expected compared with age- and sex-matched white US population mortality rates (P=.77). Independent predictors of death were age at diagnosis, "burned out" HCM, and history of transient ischemic attack or stroke; use of an implantable cardioverter defibrillator (ICD) was inversely related to death. After exclusion of patients with an ICD, there was no difference in survival compared with age- and sex- matched individuals (P=.39); age, previous transient ischemic attack/stroke, and burned out HCM were predictors of death. CONCLUSION:In this cohort, patients with NO-HCM had similar survival rates as age- and sex-matched white US population mortality rates. Although use of an ICD was inversely related to death, no differences in overall survival were seen after those patients were excluded. Burned out HCM was independently associated with an increased risk of death, identifying a subset of patients who may benefit from more aggressive therapies.