Heart & Circulation

Cardiomyopathy: Symptoms, Causes, Diagnosis, and Treatment

A patient guide to cardiomyopathy — disease of the heart muscle. Covers dilated, hypertrophic, and restrictive types, common symptoms, causes including genetics and alcohol, diagnosis with ECG and cardiac MRI, and treatment options including medicines and ICDs.

14 min read

Cardiomyopathy: Symptoms, Causes, Diagnosis, and Treatment

Cardiomyopathy is a disease of the heart muscle — a condition in which the heart muscle itself becomes structurally or functionally abnormal, impairing the heart’s ability to pump blood effectively. It is one of the most important causes of heart failure, arrhythmias, and sudden cardiac death, and can affect people of all ages, including children and young adults.

Unlike coronary artery disease — which is caused by blockages in the arteries supplying the heart — cardiomyopathy arises from within the heart muscle itself. Understanding which type you have, and why it has developed, is central to getting the right treatment.

What Is Cardiomyopathy?

The heart is a muscular pump. In cardiomyopathy, that muscle becomes diseased — whether by becoming enlarged and weak, excessively thickened, or abnormally stiff. Each of these changes impairs how efficiently the heart pumps blood to the body and lungs.

Cardiomyopathy is classified into three main types based on the structural change in the heart muscle.

Types of Cardiomyopathy

Dilated Cardiomyopathy (DCM)

The most common type. The left ventricle (the main pumping chamber) becomes enlarged and weakened, losing its ability to contract powerfully. The ejection fraction — the percentage of blood pumped out with each beat — is reduced, typically below 40%.

Key features:

  • Enlarged, poorly contracting left ventricle
  • Reduced ejection fraction, classified as heart failure with reduced ejection fraction (HFrEF)
  • Risk of blood clot formation within the dilated chamber
  • Progressive heart failure symptoms: breathlessness, fatigue, ankle swelling

Common causes:

  • Genetic mutations (familial DCM — present in 30–40% of cases)
  • Prior viral myocarditis (inflammation of the heart muscle following infection)
  • Excessive alcohol use (alcoholic cardiomyopathy)
  • Chemotherapy — particularly anthracyclines (doxorubicin, epirubicin) and trastuzumab (Herceptin)
  • Peripartum cardiomyopathy (developing in late pregnancy or within five months of delivery)
  • Idiopathic (no identifiable cause found, in approximately a third of cases)

Hypertrophic Cardiomyopathy (HCM)

The second most common type and the most common inherited heart disease, affecting approximately 1 in 500 people. The heart muscle — particularly the interventricular septum (the wall between the two ventricles) — becomes abnormally thickened. This makes it harder for the heart to fill and, in some cases, creates obstruction to blood flowing out of the heart.

Key features:

  • Thickened heart muscle, typically the septum
  • Usually normal or elevated ejection fraction — the heart contracts well but fills poorly
  • Outflow obstruction in approximately two-thirds of people (hypertrophic obstructive cardiomyopathy, HOCM)
  • Risk of dangerous arrhythmias and sudden cardiac death, particularly in young people and athletes
  • Frequently runs in families; often first detected in adolescence or early adulthood

Causes:

  • Mutations in genes encoding sarcomere proteins (the contractile machinery of heart muscle cells) — identified in approximately 50–60% of cases
  • In many cases a genetic mutation is found and targeted family screening becomes possible

Restrictive Cardiomyopathy

The least common of the primary types. The heart muscle becomes abnormally stiff, limiting its ability to relax and fill properly between beats. Ejection fraction may be initially preserved, but the high filling pressures cause symptoms similar to heart failure.

Key features:

  • Stiff, non-compliant heart muscle
  • Impaired filling — high pressures behind the heart, causing fluid back-up into the lungs
  • Symptoms of heart failure despite relatively normal ejection fraction
  • Can be difficult to distinguish from constrictive pericarditis

Common causes:

  • Cardiac amyloidosis — accumulation of abnormal protein (amyloid) deposits in the heart muscle; cardiac transthyretin amyloidosis (ATTR-CM) is increasingly recognised in older adults with unexplained thickened heart walls and is now a focus of specific drug therapy
  • Haemochromatosis (iron overload)
  • Sarcoidosis (inflammatory disease affecting multiple organs)
  • Post-radiotherapy cardiac fibrosis

Other Types

  • Arrhythmogenic cardiomyopathy (ACM) — fatty or fibrous tissue replaces heart muscle, predominantly in the right ventricle, causing arrhythmias and risk of sudden cardiac death; strongly associated with mutations in desmosomal protein genes
  • Peripartum cardiomyopathy — dilated cardiomyopathy presenting in late pregnancy or within five months of delivery; many women recover fully with early treatment, but some develop persistent heart failure
  • Left ventricular non-compaction (LVNC) — a developmental abnormality producing an abnormal spongy appearance of the heart muscle; can cause heart failure and arrhythmias

Symptoms

Cardiomyopathy can be present for years before symptoms develop. When they appear, they reflect the heart’s reduced ability to pump efficiently.

Common symptoms include:

  • Shortness of breath — on exertion initially, progressing to breathlessness at rest in advanced disease; waking at night breathless (paroxysmal nocturnal dyspnoea); needing extra pillows to sleep (orthopnoea)
  • Fatigue and reduced exercise tolerance — persistent tiredness, inability to sustain physical activity
  • Palpitations — an awareness of the heartbeat; may represent atrial fibrillation, benign ectopic beats, or more dangerous ventricular arrhythmias
  • Dizziness or light-headedness — particularly on exertion or standing; may reflect low blood pressure or arrhythmia
  • Ankle and leg swelling — fluid accumulation (oedema) from heart failure
  • Chest pain or pressure — can occur in hypertrophic cardiomyopathy due to increased wall stress and impaired filling
  • Fainting (syncope) or near-fainting — particularly important in hypertrophic cardiomyopathy; may indicate a dangerous arrhythmia and warrants urgent assessment

In hypertrophic cardiomyopathy: symptoms often worsen with exertion or after meals. Some people experience exertional chest pain mimicking angina.

Seek emergency care immediately for sudden collapse, loss of consciousness, severe chest pain, or a rapid pounding heartbeat with dizziness.

Causes

Genetic Causes

  • Hypertrophic cardiomyopathy: most commonly caused by inherited mutations in sarcomere protein genes (MYH7, MYBPC3, and others); autosomal dominant pattern — a 50% chance of passing the mutation to each child
  • Dilated cardiomyopathy: familial in at least 30–40% of cases; multiple genes implicated (TTN, LMNA, SCN5A, and others); family screening is recommended after diagnosis
  • Arrhythmogenic cardiomyopathy: strongly genetic (PKP2 and other desmosomal protein genes)

Lifestyle and Acquired Causes

  • Excessive alcohol use — one of the most common reversible causes of dilated cardiomyopathy; alcoholic cardiomyopathy can improve significantly with abstinence
  • Viral myocarditis — inflammation of the heart muscle following viral infection (including enteroviruses, parvovirus B19); may progress to dilated cardiomyopathy
  • Chemotherapy and cardiotoxic medicines — anthracycline chemotherapy, trastuzumab, and certain other cancer drugs can cause dilated cardiomyopathy; risk is related to cumulative dose and is monitored with echocardiography during and after treatment

Infiltrative and Inflammatory Causes

  • Cardiac amyloidosis — accumulation of misfolded protein in the heart muscle; increasingly recognised in older adults with unexplained thickened heart walls and heart failure; tafamidis (for ATTR type) is now an approved treatment
  • Sarcoidosis — granulomatous inflammation affecting the heart; can cause arrhythmias, heart block, and heart failure
  • Haemochromatosis — iron overload causing restrictive cardiomyopathy; treatable with phlebotomy

Diagnosis

Cardiomyopathy is diagnosed using a combination of clinical assessment and investigations. If cardiomyopathy is suspected — from symptoms, family history, or an abnormal ECG — referral to a cardiologist is appropriate.

ECG (Electrocardiogram)

Often abnormal, though findings are non-specific and vary by type:

  • Hypertrophic cardiomyopathy: commonly shows ST changes, deep Q waves, and signs of left ventricular hypertrophy
  • Dilated cardiomyopathy: may show bundle branch block, ST changes, or atrial fibrillation
  • Arrhythmogenic cardiomyopathy: may show epsilon waves or right bundle branch block

Echocardiogram (Heart Ultrasound)

The most important initial investigation:

  • Measures the size and function of the heart chambers
  • Assesses ejection fraction (reduced vs preserved)
  • Measures wall thickness, identifying hypertrophy characteristic of HCM
  • Detects outflow tract obstruction in hypertrophic cardiomyopathy
  • Assesses valve function and filling pressures

Cardiac MRI

The gold standard for characterising heart muscle abnormalities:

  • Provides detailed assessment of wall motion, fibrosis, and infiltration
  • Gadolinium late enhancement identifies areas of scarring — important for risk stratification in HCM and DCM
  • Distinguishes between different causes (amyloid, sarcoidosis, myocarditis, HCM)
  • Used in arrhythmogenic cardiomyopathy diagnosis and monitoring

Blood Tests

  • BNP or NT-proBNP — markers of heart strain, elevated in heart failure caused by cardiomyopathy
  • Full blood count, renal and liver function, thyroid function
  • Iron studies and ferritin — to exclude haemochromatosis
  • Troponin — elevated in myocarditis and some restrictive cardiomyopathies
  • Specific tests for amyloidosis (TTR gene analysis, technetium pyrophosphate scintigraphy)

Genetic Testing

Genetic testing is increasingly used to:

  • Identify the underlying mutation in hypertrophic or dilated cardiomyopathy
  • Guide family screening
  • Assist risk stratification (some mutations in DCM, such as LMNA, carry higher arrhythmia risk)

If a pathogenic mutation is confirmed, first-degree relatives (parents, siblings, children) should be offered screening — each has up to a 50% chance of carrying the same variant.

Holter Monitor / Event Recorder

Continuous ECG recording over 24–48 hours or longer — detects arrhythmias not captured on a standard resting ECG. Important in HCM (arrhythmia risk assessment) and arrhythmogenic cardiomyopathy.

Exercise Stress Testing

  • Assesses functional capacity
  • In HCM: measures blood pressure response to exercise (an abnormal response signals higher risk)
  • Detects exercise-induced arrhythmias

Treatment

Treatment depends on the type of cardiomyopathy, its severity, and the underlying cause.

Medicines

For dilated cardiomyopathy with reduced ejection fraction: The same evidence-based heart failure medicines apply:

  • ACE inhibitors or ARBs (e.g. ramipril, candesartan) — reduce cardiac workload, protect heart function, and reduce fibrosis
  • Beta blockers (e.g. bisoprolol, carvedilol) — reduce heart rate, protect against arrhythmias, and improve ejection fraction over time
  • Mineralocorticoid receptor antagonists (MRAs) (e.g. spironolactone, eplerenone) — reduce fluid retention and cardiac fibrosis
  • SGLT2 inhibitors (e.g. dapagliflozin, empagliflozin) — proven to reduce hospitalisations and improve outcomes in heart failure
  • Diuretics — relieve fluid build-up and breathlessness (symptom control)

See also: Heart Failure: Symptoms, Causes, Diagnosis, and Treatment

For hypertrophic cardiomyopathy:

  • Beta blockers — reduce heart rate, improve filling time, and reduce outflow obstruction
  • Non-dihydropyridine calcium channel blockers (e.g. verapamil) — alternative for those who cannot tolerate beta blockers
  • Mavacamten — a novel cardiac myosin inhibitor approved specifically for obstructive HCM (HOCM); reduces outflow obstruction and improves symptoms and exercise capacity; available in Australia under specific criteria

For cardiac amyloidosis (ATTR type):

  • Tafamidis — a TTR stabiliser proven to reduce mortality and hospitalisation in ATTR cardiomyopathy; available in Australia under specific criteria
  • Other emerging agents (diflunisal, patisiran, RNA interference therapies) are available in specialist centres

For alcoholic cardiomyopathy:

  • Alcohol abstinence — the most important intervention; the heart muscle can recover substantially if alcohol use is stopped early

Implantable Cardioverter-Defibrillator (ICD)

An ICD is a device implanted under the skin that continuously monitors heart rhythm and delivers a shock to restore normal rhythm if a dangerous arrhythmia is detected.

ICDs are recommended for:

  • Dilated or other cardiomyopathies with severely reduced ejection fraction (typically below 35%) after at least three months of optimal medical therapy
  • Survivors of sudden cardiac arrest or sustained ventricular tachycardia
  • Hypertrophic cardiomyopathy with high estimated five-year risk of sudden cardiac death (calculated using an ESC risk model incorporating family history, degree of hypertrophy, and arrhythmia history)
  • Arrhythmogenic cardiomyopathy with significant structural involvement or sustained arrhythmias

Cardiac Resynchronisation Therapy (CRT)

In dilated cardiomyopathy with bundle branch block, where the two ventricles contract out of sync, CRT uses a specialised pacemaker to coordinate ventricular contraction. This improves ejection fraction, reduces symptoms, and reduces mortality. It is often combined with ICD function (CRT-D).

Septal Reduction for Obstructive Hypertrophic Cardiomyopathy

When symptoms persist in hypertrophic obstructive cardiomyopathy despite medicines, two procedures can reduce the outflow obstruction:

  • Surgical myectomy — surgical removal of excess septal muscle; the preferred option at specialist centres and in younger patients
  • Alcohol septal ablation — controlled injection of alcohol into a septal artery causing localised infarction of the obstructing muscle; an alternative for patients unsuitable for surgery

Lifestyle

  • Alcohol abstinence — essential in alcoholic cardiomyopathy; important across all types as alcohol worsens heart muscle function
  • Exercise — generally encouraged in dilated cardiomyopathy with appropriate guidance; cardiac rehabilitation programmes are highly recommended. In hypertrophic cardiomyopathy, competitive sport and high-intensity exercise are typically restricted due to arrhythmia risk; discuss your specific limits with your cardiologist
  • Salt and fluid restriction — as for heart failure, when fluid retention is present
  • Genetic counselling — for those with inherited cardiomyopathies; important for family planning and family screening decisions

Heart Transplantation

In advanced cardiomyopathy not responding to medical and device therapy, heart transplantation may be considered. Left ventricular assist devices (LVADs) can bridge patients to transplantation or serve as long-term destination therapy.

Relationship to Heart Failure

Cardiomyopathy is one of the most common causes of heart failure. When the heart muscle is diseased:

  • In dilated cardiomyopathy, the weakened ventricle cannot pump enough blood → heart failure with reduced ejection fraction (HFrEF)
  • In hypertrophic and restrictive cardiomyopathy, the stiff or poorly-filling ventricle leads to raised filling pressures → heart failure symptoms despite normal or preserved ejection fraction

The treatment overlap is substantial — medicines proven to reduce mortality in heart failure (ACE inhibitors, beta blockers, MRAs, SGLT2 inhibitors) are also the main pharmacological treatment for dilated cardiomyopathy.

See: Heart Failure: Symptoms, Causes, Diagnosis, and Treatment

Relationship to Arrhythmias

Cardiomyopathy significantly increases the risk of:

  • Atrial fibrillation (AF) — very common in both dilated and hypertrophic cardiomyopathy; the dilated, fibrotic atria provide the substrate for AF, which in turn worsens heart failure
  • Ventricular tachycardia and fibrillation — life-threatening arrhythmias that can cause sudden cardiac death; particularly important in arrhythmogenic cardiomyopathy and HCM
  • Sudden cardiac death — HCM is the most common cause of sudden cardiac death in young people and competitive athletes

In all types of cardiomyopathy, arrhythmia monitoring and individualised risk assessment are important parts of ongoing management.

See: Atrial Fibrillation: Symptoms, Risks, and Treatment

FAQ

Q: Can cardiomyopathy go away? Some types can substantially improve with treatment. Alcoholic cardiomyopathy often recovers significantly with abstinence. Peripartum cardiomyopathy recovers fully in around 50% of cases. Myocarditis-related cardiomyopathy can also resolve. However, genetic forms of HCM and many cases of DCM are lifelong conditions requiring ongoing management.

Q: Can I exercise with cardiomyopathy? This depends on the type and severity. For dilated cardiomyopathy, supervised exercise and cardiac rehabilitation are generally recommended and improve outcomes. For hypertrophic cardiomyopathy, competitive sport and high-intensity exercise are typically restricted due to arrhythmia risk. Always discuss your specific exercise plan with your cardiologist before changing your activity.

Q: Should my family be tested if I have cardiomyopathy? If a genetic cause is identified, first-degree relatives — parents, siblings, and children — should be offered clinical and, where appropriate, genetic screening. Even if no genetic cause is found, clinical screening of close family members is recommended for dilated and hypertrophic cardiomyopathy. Your cardiologist will guide the screening process.

Q: What happens at a cardiomyopathy specialist appointment? Your cardiologist will review symptoms, medications, and recent investigations. For HCM, this typically includes a repeat echocardiogram, a Holter monitor, and exercise testing to assess arrhythmia risk. For DCM, follow-up focuses on echocardiographic response to treatment, medication optimisation, and ICD review if applicable. Specialist cardiomyopathy centres provide multidisciplinary review including genetic counselling services.

Q: Is pregnancy safe with cardiomyopathy? Pregnancy places significant additional demands on the heart. Women with dilated cardiomyopathy or prior peripartum cardiomyopathy with incomplete recovery require pre-conception counselling and specialist cardio-obstetric monitoring throughout pregnancy. In hypertrophic cardiomyopathy, most women tolerate pregnancy well with appropriate monitoring. Individual risk varies — always discuss pregnancy planning with your cardiologist.

Further Reading

Educational only — not a substitute for professional medical advice. Always speak with your cardiologist or GP about your specific situation.