Dilated Cardiomyopathy

Dilated cardiomyopathy: is the commonest (90%) of the cardiomyopathies (‘heart muscle disease of unknown cause’); characterised by hypertrophy and dilatation of all four chambers of the heart. This condition may occur at any age as slow, progressive CHF.

Aetiology: although the cause in a specific case is unknown, certain pathogenetic pathways are suspected to contribute in many cases:

• Genetic defect: in ~20% cases there seems to be a degree of familial incidence

• Alcohol toxicity: attributable possibly to direct toxicity of alcohol or a metabolite (esp. acetaldehyde)

• Peripartum cardiomyopathy: designation given to a globally dilated heart discovered within several months before or after delivery

• Postviral myocarditis: occasional cases in which endomyocardial biopsy specimens have documented the progression of myocarditis to dilated cardiomyopathy

Others include nutritional deficiency (e.g. thiamine) and some chemotherapeutic agents (e.g. Adriamycin); these causes all give a similar disease pattern.

Morphology:

Grossly the heart may show:

• Cardiomegaly (up to 3 normal)

• Heart is dilated and flabby

• Poor contractile function and stasis can lead to mural thrombi

• Patchy fibrous scarring of myocardium and endocardium.

Histologically the heart may show:

• 25% have no significant alterations

• The remainder have diffuse myocyte hypertrophy and variable interstitial myocardial fibrosis

Clinical features:

The disease is characterised by forward failure with reduced cardiac output. There may be mitral incompetence which is due to dilatation of the left ventricle.

Death from progressive heart failure is likely to occur within a year or two (only ~ 25% of patients survive beyond 5 years) unless heart transplantation is performed.

Category: Pharmacology Notes