Background: A previous study suggested that severe left-ventricular hypertrophy (maximum wall thickness > or = 30 mm) in patients with hypertrophic cardiomyopathy is associated with a risk of sudden cardiac death sufficient to warrant consideration for implantation of a cardioverter defibrillator (ICD). However, the prognostic significance of left-ventricular hypertrophy in relation to other clinical risk factors is poorly characterised.
Methods: We studied 630 patients consecutively referred to one hospital in London, UK (mean age 37 years [SD 16]; 382 male; mean follow-up 59 months). Patients underwent two-dimensional and doppler echocardiography, upright exercise testing, and Holter monitoring.
Findings: 39 patients died suddenly or had an appropriate ICD discharge; nine died from progressive heart failure; 11 from other cardiovascular causes and 23 from non-cardiac causes. There was a trend towards higher probability of sudden death or ICD discharge with increasing wall thickness (p=0.029, relative risk per 5 mm increment 1.31 [95% CI 1.03-1.66]). Of the 39 patients who died suddenly or had an ICD discharge, ten had a wall thickness of 30 mm or more. Patients with wall thickness of 30 mm or more had higher probability of sudden death or ICD discharge than patients with wall thickness less than 30 mm (p=0.049, 2.07 [1.00-4.25]. When considered together, the number of additional risk factors (one to three) was a better predictor of risk of sudden death or ICD discharge than wall thickness (p=0.0001, relative risk per additional factor 2.00 [1.43-2.79] vs p=0.058, 1.26 per 5 mm increment [0.99-1.60]). There was no relation between the pattern of hypertrophy and survival.
Interpretation: The risk of sudden death associated with a wall thickness of 30 mm or more in patients without other risk factors is insufficient to justify aggressive prophylactic therapy. Most sudden deaths occurred in patients with wall thickness less than 30 mm, so the presence of mild hypertrophy cannot be used to reassure patients that they are at low risk.