Cardiomyopathies (Dilated, Hypertrophic, Restrictive)

The cardiomyopathies are diseases of the heart muscle in which the myocardium is structurally and functionally abnormal in the absence of disease sufficient to explain it from coronary obstruction, hypertension, valve disease, or congenital defect alone. They are conventionally grouped by phenotype into dilated, hypertrophic, and restrictive forms, each defined by a characteristic pattern of chamber size, wall thickness, and filling behaviour.

Definition

A cardiomyopathy is a myocardial disorder in which the heart muscle is structurally and functionally abnormal, classified by morphological and functional phenotype (dilated, hypertrophic, restrictive, and other forms) rather than solely by cause.

Scope

This topic covers the concept of a primary disease of heart muscle and the three classical morphological phenotypes — dilated, hypertrophic, and restrictive — together with their defining structural and physiological features and the genetic and acquired causes that underlie them. It is a reference entry on definition and classification, not a guide to management of any individual.

Core questions

• Is the dominant phenotype dilatation, hypertrophy, or restriction to filling?
• Is the disease primarily genetic, acquired, or mixed in origin?
• How does each phenotype alter contraction, filling, and the risk of arrhythmia?

Key concepts

• Dilated cardiomyopathy (ventricular dilatation, reduced systolic function)
• Hypertrophic cardiomyopathy (unexplained wall thickening)
• Restrictive cardiomyopathy (impaired filling, preserved or near-normal wall thickness)
• Phenotype-based classification
• Sarcomeric and other genetic causes
• Left ventricular outflow tract obstruction
• Risk of arrhythmia and sudden cardiac death

Mechanisms

In dilated cardiomyopathy the ventricle enlarges and contracts poorly, reducing systolic ejection. In hypertrophic cardiomyopathy the ventricular wall is abnormally thickened in a manner unexplained by loading conditions, often due to sarcomeric gene variants, and in some patients thickening of the septum produces dynamic obstruction of the left ventricular outflow tract. In restrictive cardiomyopathy the walls are stiff and resist filling, so diastolic pressures rise while wall thickness and systolic function may be relatively preserved. Modern classification groups these by morphological and functional phenotype, then sub-characterises by genetic and acquired aetiology, because a single phenotype can arise from many causes (Maron, 2006; Elliott, 2008; Arbelo, 2023). Several forms carry an elevated risk of ventricular arrhythmia and sudden cardiac death.

Clinical relevance

Cardiomyopathies are an important cause of heart failure, arrhythmia, and sudden cardiac death, including in young and otherwise healthy people, and several forms are inherited, which gives them relevance for family evaluation. Understanding the phenotypes aids interpretation of imaging and the cardiology literature. This entry is descriptive and is not a basis for individual diagnosis, risk stratification, or treatment.

Epidemiology

Hypertrophic cardiomyopathy is among the more common inherited cardiac conditions and is a recognised cause of sudden death in young athletes; dilated cardiomyopathy is a frequent cause of heart failure with reduced ejection fraction and a common indication for transplantation; restrictive forms are comparatively uncommon. Precise estimates vary with the definition and ascertainment method used (Maron, 2006; Arbelo, 2023).

History

The term cardiomyopathy came into use in the mid-twentieth century to denote heart-muscle disease distinct from coronary, valvular, and hypertensive causes. Classification evolved from purely morphological schemes toward systems that integrate phenotype with genetic and acquired aetiology, reflecting advances in cardiac imaging and genetics (Maron, 2006; Elliott, 2008). The 2023 ESC guideline consolidated a phenotype-led, aetiology-aware framework (Arbelo, 2023).

Debates

Should cardiomyopathies be classified by phenotype or by aetiology?

Influential statements differ in emphasis: some frameworks group conditions primarily by morphological and functional phenotype, while others foreground genetic and acquired aetiology. Contemporary guidance integrates both, classifying by phenotype and then characterising cause.

Seminal works

• maron-2006
• elliott-2008
• arbelo-2023

Frequently asked questions

What are the three classical types of cardiomyopathy?

Dilated cardiomyopathy (an enlarged, weakly contracting ventricle), hypertrophic cardiomyopathy (abnormal thickening of the heart muscle not explained by loading), and restrictive cardiomyopathy (stiff walls that resist filling). Other phenotypes, such as arrhythmogenic forms, are also recognised.

Are cardiomyopathies inherited?

Many are, at least in part. Hypertrophic cardiomyopathy and a substantial share of dilated cardiomyopathy have genetic causes, which is why family evaluation is part of how these conditions are approached, though acquired causes also exist.