Dilated cardiomyopathy is characterised by ventricular chamber enlargement and contractile dysfunction with normal left ventricular wall thickness. The right ventricle may also be dilated and dysfunctional. Dilated cardiomyopathy is the most frequent reason for heart transplantation.
It is a biochemical abnormality of cardiac muscle and is a diagnosis of exclusion, particularly excluding ischaemic and hypertensive heart disease, although the clinical effects may be identical.
- It is difficult to know the true prevalence but is estimated at around 2 in 10,000.
- Genetic inheritance arises in 30-48% of patients.
- Mutations in 60 genes have been associated with dilated cardiomyopathy.
- Genes that encode for sarcomeric, cytoskeletal, nuclear membrane, dystrophin-associated glycoprotein complex and desmosomal proteins are the principal genes involved.
- Usually occurs in adults aged 20-60 years.
- More common in males.
- Occurs more often in African-Americans than in Caucasians.
Finding an underlying cause can often be very difficult, especially as many patients have more than one underlying risk factor. Causes may include:
- Idiopathic cause
- Genetic cause - usually autosomal dominant with incomplete penetrance, although there are rare X-linked cases (including the rare Barth syndrome)
- Autoimmune - eg, rheumatoid arthritis, SLE
- Drug abuse - eg, cocaine, amfetamines and heroin
- Drugs - eg, phenothiazines
- Peripartum cardiomyopathy
- Infiltrative: haemochromatosis, amyloidosis, glycogen storage disease
- Chronic Chagas' cardiomyopathy
- HIV infection
- Other infectious disease - eg, adenovirus, Coxsackievirus, cytomegalovirus, toxoplasmosis, Lyme disease
- Clinical presentation ranges from symptomless forms to heart failure, stroke from thromboembolism, arrhythmias, and sudden cardiac death.
- It may present with the effects of emboli before other symptoms appear.
- Most cases of dilated cardiomyopathy present as congestive heart failure: dyspnoea, weakness, fatigue, oedema, raised JVP, pulmonary congestion, cardiomegaly, loud third and/or fourth heart sound.
- Fatigue, weakness, and exercise intolerance are often progressive.
- A viral prodrome with malaise, flu-like illness or chest pain from antecedent myocarditis may be present.
- Atrial fibrillation may develop.
- A family history should be used to identify affected relatives for clinical and genetic assessment.
Investigations may include the following:
- CXR: cardiomegaly, pulmonary oedema.
- ECG: may show only sinus tachycardia or an intraventricular conduction delay, left bundle branch block, or nonspecific changes in ST and T waves.
- Echocardiogram: marked dilation of the left ventricular cavity and reduced systolic and diastolic function. May also show mitral regurgitation, tricuspid regurgitation and mural thrombus.
- B-type natriuretic peptide (BNP) can be of clinical use in diagnosis, management, and prognosis of patients, especially those with heart failure.
- Investigations to determine the underlying cause may be required.
- Cardiac catheterisation: usually shows raised filling pressure.
- Coronary arteriography: usually shows normal vessels.
- Endomyocardial biopsies: some patients are shown to have specific heart muscle disorders - eg, myocarditis, amyloidosis, sarcoidosis or haemochromatosis.
Management is aimed at improving cardiac function, treating symptoms and preventing complications. The treatment is therefore the same as for treating heart failure.
- Loop diuretics and thiazide diuretics: for all symptomatic patients with fluid overload.
- Angiotensin-converting enzyme (ACE) inhibitors: for patients with reduced left ventricular ejection fraction. Angiotensin II receptor antagonists can be used as an alternative. ACE inhibitors and beta-blockers improve function even if patients are asymptomatic.
- Digoxin: for patients with inadequate response to ACE inhibitors and diuretics and for patients with atrial fibrillation and rapid ventricular rates.
- Beta-blockers: indicated for all patients as they have been shown to improve survival.
- Spironolactone: also shown to improve survival.
- Nitrates: for patients with diastolic dysfunction and pulmonary congestion.
- Warfarin: for patients with atrial fibrillation or history of systemic or pulmonary embolism.
- Biventricular pacing (using a cardiac resynchronisation device):
- Can improve symptoms in patients with class III and IV heart failure with marked QRS prolongation.
- Can improve survival and increase exercise tolerance.
- Implantable cardioverter defibrillator: reduces risk of sudden death in high-risk patients.
- Mitral annuloplasty or valve replacement can improve symptoms in patients with severe mitral regurgitation.
- In patients with recurrent ventricular tachycardia, catheter ablation may be beneficial.
- Response to medical therapy may be disappointing and, particularly in the young, heart transplantation or left ventricular assist devices may be required. Transplant has excellent functional results and survival rates of 80% at one year and 70% at five years.
- Research is underway into progenitor cell therapy following initial pilot trials of intracoronary stem cell infusion in acute myocardial infarction.
- Progression of the disease causes progressive heart failure.
- Associated conduction defects are often present, and there is also a risk of sudden cardiac death from ventricular arrhythmia.
- Prognosis is related to the severity of disease at initial presentation.
- Five-year survival for patients with dilated cardiomyopathy is about 30%. Mitral regurgitation or diastolic dysfunction is associated with a worse prognosis.
- Peripartum cardiomyopathy is associated with a high morbidity and mortality, and diagnosis is often delayed.
- Cardiac arrhythmia is often a potential trigger of sudden cardiac death.
- Accurate molecular genetic diagnosis is critical for achieving effective prognostic determination and appropriate cardiac care.
- Avoidance of excessive alcohol intake and abstinence from cocaine.
- Early diagnosis and management of any other potential cause.
Further reading and references
; Dilated cardiomyopathy. Lancet. 2010 Feb 27375(9716):752-62.
; Lamin A/C mutations in dilated cardiomyopathy. Cardiol J. 2014 May 20. doi: 10.5603/CJ.a2014.0037.
; Genetics in dilated cardiomyopathy. Biomark Med. 2013 Aug7(4):517-33. doi: 10.2217/bmm.13.77.
; European Society of Cardiology (2007)
; NICE Technology Appraisal, January 2006
; Catheter ablation of ventricular tachycardia in nonischemic heart disease. Circ Arrhythm Electrophysiol. 2012 Oct5(5):992-1000. doi: 10.1161/CIRCEP.112.971341. Epub 2012 Aug 31.
; Pathophysiology and epidemiology of peripartum cardiomyopathy. Nat Rev Cardiol. 2014 Apr 1. doi: 10.1038/nrcardio.2014.37.
; Dilated cardiomyopathy: a disease of the myocardium. Biol Pharm Bull. 201336(1):18-22.
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