Magnitude of left ventricular hypertrophy and risk of sudden death in hypertrophic cardiomyopathy.

Background: Sudden death is a possible consequence of hypertrophic cardiomy opathy. Quantification of the risk of sudden death, however, remains imprec ise for most patients with this disease. Methods: We assessed the relation between the magnitude of left ventricular hypertrophy and mortality in 480 consecutive patients with hypertrophic ca rdiomyopathy. The patients were categorized into five subgroups according t o maximal wall thickness: 15 mm or less, 16 to 19 mm, 20 to 24 mm, 25 to 29 mm, and 30 mm or more. Their ages ranged from 1 to 89 years (median, 47). Results: Over a mean follow-up period of 6.5 years, 65 of the 480 patients (14 percent) died: 23 suddenly, 15 of heart failure, and 27 of noncardiac c auses or stroke. The risk of sudden death increased progressively and in di rect relation to wall thickness (P=0.001), ranging from 0 per 1000 person-y ears (95 percent confidence interval, 0 to 14.4) for a wall thickness of 15 mm or less to 18.2 per 1000 person-years (95 percent confidence interval, 7.3 to 37.6) for a wall thickness of 30 mm or more and almost doubling from each wall-thickness subgroup to the next. The cumulative risk 20 years aft er the initial evaluation was close to zero for patients with a wall thickn ess of 19 mm or less but almost 40 percent for wall thicknesses of 30 mm or more. As compared with the other subgroups, patients with extreme hypertro phy were the youngest (mean age, 31 years), and most (41 of 43) had mild sy mptoms or no symptoms; of the 12 patients who were less than 18 years old a t the initial evaluation, 5 died suddenly. Conclusions: In hypertrophic cardiomyopathy, the magnitude of hypertrophy i s directly related to the risk of sudden death and is a strong and independ ent predictor of prognosis. Young patients with extreme hypertrophy, even t hose with few or no symptoms, appear to be at substantial long-term risk an d deserve consideration for interventions to prevent sudden death. The majo rity of patients with mild hypertrophy are at low risk and can be reassured regarding their prognosis. (N Engl J Med 2000;342:1778-85.) (C)2000, Massa chusetts Medical Society.