Lifetime Clinical Course of Hypertrophic Cardiomyopathy: Outcome of the Historical Florence Cohort Over 5 Decades.

Background: The current understanding of the clinical course and long-term outcome of patients with hypertrophic cardiomyopathy (HCM) has been extrapolated from cohorts with relatively short follow-up, usually <10 years. Extended assessments more closely reflecting HCM lifetime burden are not available.

Objectives: The purpose of this study was to report the lifetime clinical course of HCM.

Methods: We analyzed the clinical course of HCM patients diagnosed at our center from 1970 to 1992 and followed annually to the present. Cumulative incidence functions were used to estimate the incidence of HCM-related mortality (including heart failure [HF]/stroke related, sudden cardiac death [SCD]) and non-HCM related.

Results: A total of 202 patients (age 41 ± 17 years; 63% male) were followed 27 ± 6 [range: 3-50] years. Overall, 97 (48%) survived and 105 (52%) died during the particularly long follow-up; 69 deaths were related to HCM, including 53 HF related, 11 fatal embolic strokes, and 16 SCDs. Annual overall HCM-related mortality was 1.3%/y, increasing from 0.7% during the first decade to 1.8% in the second/third decade ( < 0.01), mainly driven by increase in HF-/stroke-related events (from 0.6% to 1.3%). The SCD mortality rate was similar in the 2 periods (0.1% vs 0.44%,  = 0.10). Of the 69 HCM deaths, 29 (42%) occurred before the widespread availability of effective contemporary treatment strategies and are considered potentially preventable.

Conclusions: In this unique HCM cohort followed for up to 50 years, often before contemporary therapies became widely implemented for HCM, HF frequently progressed over time, while arrhythmic SCD events were less common and remained constant over time. Despite spanning different management eras over 5 decades, HCM-related mortality remained relatively low (1.3%/y).