Aetiology, diagnosis, investigation, and management of the cardiomyopathies

Introduction

Cardiomyopathies are myocardial disorders that are not secondary to coronary disease or hypertension or to congenital, valvular, or pericardial abnormalities.1

Classification is based on morphological and functional abnormalities, although overlap between groups is considerable. The four main types of cardiomyopathy are hypertrophic, dilated, restrictive, and arrhythmogenic right ventricular. Most heart muscle disorders affect mainly left ventricular structure and function, but the right ventricle is affected in arrhythmogenic right ventricular cardiomyopathy.

Methods

I performed a literature search of all papers published in English in 1996 using Medline and the keywords cardiomyopathy and heart muscle disease. I searched the sections on cardiomyopathies and inflammatory disorders in volumes 10 and 11 (1995 and 1996) of Current Opinion in Cardiology and the supplement on the cardiomyopathies of the British Heart Journal (December 1994). Current Opinion in Cardiology lists the world literature annually and reviews subjects in which knowledge has advanced during the previous year. Earlier publications have been assimilated into current knowledge, and comprehensive coverage can be found in textbooks such as Diseases of the Heart.2

I selected papers on the basis of quality, relevance, and interest. The recent literature is extensive and has concentrated on understanding the molecular biology and pathogenesis of the disease rather than its drug treatment.

Epidemiology and prevalence

Reliable data are scarce.3 Electrocardiographic and echocardiographic screening of defined populations showed that the prevalence of hypertrophic cardiomyopathy was between 1 in 500 and 1 in 5000 in the United States.4 Dilated cardiomyopathy accounts for between 1 in 50 and 1 in 25 cases of heart failure, most being secondary to coronary disease, hypertension, and valvular disease.