Dilated cardiomyopathy

Definition

Dilated cardiomyopathy (DCM) is a primary myocardial disorder with dilatation and systolic dysfunction of the left or both ventricles that is not sufficiently explained by congenital heart disease, abnormal loading conditions (e.g. primary valve disease) or coronary artery disease. It is regarded as a common phenotypic response of the myocardium to diverse insults rather than a single disease entity.

Classification

• Genetic (primary): familial forms with autosomal dominant, X-linked, autosomal recessive, mitochondrial or polygenic inheritance.
• Acquired (secondary): infectious, toxic, tachycardia-mediated, endocrine, nutritional, systemic inflammatory, neuromuscular, peripartum.
• Modifying factors: conditions such as pregnancy can unmask a previously unnoticed DCM without being causal themselves.

Occurrence & epidemiology

The estimated lifetime prevalence is about 1 in 250. DCM can occur at any age but is most commonly diagnosed in adults younger than 50 years, and it is the most common cardiomyopathy in childhood. Men are affected more often.

Aetiopathogenesis

• Genetics: familial disease in about 30–40 % of cases; monogenic variants are identified in 25–40 % of these. The most commonly implicated genes are TTN (titin) and LMNA (lamin A/C).
• Infections: including coxsackievirus B, parvovirus B19, human herpesvirus 6, HIV, hepatitis B and C viruses, borreliosis, diphtheria, Chagas disease in endemic regions.
• Toxins: alcohol, cocaine, amphetamines, cardiotoxic cytostatic agents (e.g. anthracyclines), heavy metals, carbon monoxide, radiogenic.
• Tachycardia: persistent tachyarrhythmias, frequent ventricular ectopy or chronic right ventricular pacing can cause potentially reversible systolic dysfunction.
• Endocrine, metabolic, nutritional: hyper- and hypothyroidism, Cushing disease, acromegaly, phaeochromocytoma; thiamine, carnitine and selenium deficiency; iron overload (hemochromatosis); electrolyte disturbances.
• Systemic and inflammatory: rheumatoid arthritis, systemic lupus erythematosus, systemic sclerosis, sarcoidosis, granulomatosis with polyangiitis, giant cell and eosinophilic myocarditis, hypereosinophilic syndrome.
• Neuromuscular: dystrophinopathies (Duchenne, Becker), Emery-Dreifuss, limb-girdle and myotonic dystrophy, Friedreich ataxia.
• Peripartum.

Clinical features

• Usually insidious onset with gradually progressive symptoms; abrupt onset with acute myocarditis, takotsubo or tachycardia-mediated cardiomyopathy.
• Left ventricular dysfunction: exertional dyspnea, orthopnea, fatigue.
• Right ventricular involvement: peripheral edema, hepatomegaly, abdominal distension, raised jugular venous pressure.
• Examination: third or fourth heart sound, murmur of mitral or tricuspid regurgitation, displaced apex beat, pulsus alternans in severe disease.
• Arrhythmias: atrial and ventricular arrhythmias up to sudden cardiac death due to malignant ventricular tachyarrhythmias.

Diagnosis

• History: detailed family history (early-onset heart disease, heart failure, sudden death), also as a basis for genetic testing.
• Echocardiography: left ventricular dilatation with global hypokinesis and atrial enlargement; functional mitral and tricuspid regurgitation due to annular dilatation and papillary muscle displacement; sometimes regional wall motion abnormalities; contrast echo to exclude ventricular thrombus.
• Cardiac MRI: tissue characterisation; patterns of inflammation and late gadolinium enhancement point to specific causes (e.g. myocarditis, infiltrative disease).
• ECG and ambulatory ECG recording: normal or T-wave changes, left bundle branch block, prolonged AV conduction, atrial fibrillation; ectopy and non-sustained ventricular tachycardia are common.
• Chest X-ray: enlarged cardiac silhouette, splaying of the carina, interstitial edema, pleural effusions.
• Laboratory: natriuretic peptides usually raised; depending on the situation iron studies, thyroid function, viral serology and nucleic acid testing, troponin, liver and renal function.
• Ischemia testing: exclusion of obstructive coronary artery disease.
• Others: PET when cardiac sarcoidosis is suspected; endomyocardial biopsy in selected cases (e.g. suspected giant cell or eosinophilic myocarditis).

Keep learning in the app

Further reading (open access)

1. MSD Manual Professional: Dilated Cardiomyopathy
2. StatPearls: Dilated Cardiomyopathy

Cross-references