Relation between severity of left-ventricular hypertrophy and prognosis in patients with hypertrophic cardiomyopathy

Summary

Background

A previous study suggested that severe left-ventricular hypertrophy (maximum wall thickness ⩾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.

Introduction

Many clinical features have been suggested as markers of the risk of sudden death in patients with hypertrophic cardiomyopathy, including an adverse family history, syncope, non-sustained ventricular tachycardia, bloodpressure response on exercise, and left-ventricular wall thickness.1, 2, 3, 4, 5, 6, 7, 8, 9 We have shown that patients with two or more of these established risk factors have a risk of sudden death that warrants consideration for implantation of a cardioverter defibrillator (ICD).¹⁰ Spirito and colleagues have suggested that severe left-ventricular hypertrophy (wall thickness ⩾30 mm) alone is sufficient to warrant ICD therapy.⁸ However, this suggestion has profound clinical implications, not least because over 10% of reported patients have a wall thickness in this range. The aim of our study was to assess the influence of the extent and distribution of hypertrophy, and the presence of other risk factors, on the usefulness of wall thickness as a marker of risk of sudden death.