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Cardiomyopathies

Introduction and epidemiology

According to ESC, cardiomyopathies are defined by structural and functional abnormalities of the ventricular myocardium that are unexplained by coronary artery disease or abnormal loading conditions. This definition does not include diseases of the myocardium secondary to coronary artery disease or hypertension.

However, terms like “ischaemic cardiomyopathy” and “hypertensive cardiomyopathy” are used clinically to describe myocardial damage following chronic ischaemia and hypertension, respectively, despite not being true cardiomyopathies according to the ESC definition.

Types

• Main cardiomyopathies
  • Dilated cardiomyopathy
  • Hypertrophic cardiomyopathy
  • Restrictive cardiomyopathy
  • Arrhythmogenic right ventricular cardiomyopathy
  • Left ventricular non-compaction cardiomyopathy
• Other cardiomyopathies
  • Tachycardia-induced cardiomyopathy
  • Takotsubo cardiomyopathy
  • Ischaemic cardiomyopathy
  • Hypertensive cardiomyopathy
  • Peripartum cardiomyopathy

Dilated cardiomyopathy

Introduction and epidemiology

Dilated cardiomyopathy (DCM) is a form of cardiomyopathy characterised by dilation of all four heart chambers, in the absence of ischaemia heart disease, hypertension, valvular disease, and congenital heart disease. The ejection fraction is <45% and the left ventricular end-diastolic volume is >117% of forecasted based on body surface area.

DCM is the most common cardiomyopathy, affecting 1/250. The prognosis is poor with a 5-year survival rate of 50%.

Etiology

• Idiopathic
• Familial (genetic) – mutations in cytoskeletal, sarcomeric, nuclear, etc. proteins
• Secondary
  • Myocarditis
  • Pregnancy (peripartum DCM)
  • Alcohol
  • Infiltration (sarcoidosis, amyloidosis)
  • Cardiotoxic drugs

Pathomechanism

Dilation of the chambers causes systolic heart failure.

Clinical features

Patients can be asymptomatic. Symptomatic patients have features of right and/or left-sided heart failure, including fatigue, weakness, exercise intolerance, chest pain, palpitations, and tachycardia.

Diagnosis and evaluation

X-ray shows enlargement of the cardiac silhouette, and possibly signs of pulmonary congestion. Echocardiography shows dilation of all four chambers, decreased EF, and secondary mitral and tricuspid regurgitation.

MRI is the gold standard for evaluation, as it can measure the volumes of the chambers. It’s also helpful in the evaluation of myocarditis, a common cause.

Treatment

There is no specific treatment for DCM. If there’s an underlying disease, it should be treated. Treatment for heart failure is often necessary. Implantation of ICD is important to prevent sudden cardiac death by V-fib. Heart transplant is the only curative treatment.

Hypertrophic cardiomyopathy

Introduction and epidemiology

Hypertrophic cardiomyopathy (HCM) is a form of cardiomyopathy characterised by left ventricular hypertrophy in the absence of a provoking disease like hypertension or aortic stenosis. The hypertrophy is often asymmetric.

Hypertrophic obstructive cardiomyopathy (HOCM) is a subtype of HCM characterised by obstruction of the left ventricular outflow tract due to excessive hypertrophy of the ventricular septum.

It’s a common cause of sudden cardiac death, especially in athletes. It may also progress into left ventricular dilation. It’s the second most common CMP, affecting 1/500.

Etiology

HCM is a genetic disorder, most commonly caused by mutations in sarcomeric proteins like myosin. Inheritance is autosomal dominant with varying penetrance.

Pathomechanism

HCM causes diastolic dysfunction and increased filling pressure. During systole, there is a narrowing of the LV outflow tract and increased ejection speed. This increased ejection speed decreases the pressure in this region, causing the anterior leaflet of the mitral valve to be pulled in that direction. This is called systolic anterior motion (SAM) of the anterior cusp of the mitral valve, which can intermittently obstruct the outflow tract, causing a sudden decrease in CO. This phenomenon occurs more frequently during exercise.

HCM predisposes to development of arrhythmias, including fatal ones.

Clinical features

Many are asymptomatic. Possible symptoms include dyspnoea, angina pectoris, and syncope (due to LVOT obstruction.

For some affected people, sudden cardiac death is the first manifestation of HCM.

Diagnosis and evaluation

ECG shows signs of left ventricular hypertrophy and strain. Echocardiography shows left ventricular hypertrophy, a septum which is thicker than the posterior wall, normal LV chamber size. SAM may also be visualised.

MRI is the gold standard for the evaluation. 1^st degree relatives should be screened for the condition.

Treatment

There’s no specific treatment. Strenuous physical activity should be avoided to prevent sudden cardiac death. In case of significant LVOT obstruction, medical treatment is indicated, but it’s not certain whether medical treatment is indicated for HCM without significant LVOT obstruction. Medical treatment includes beta blockers, CCBs, and antiarrhythmic drugs.

Prevention of SCD by ICD implantation is generally indicated but depends on the patients calculated risk.

Procedures to reduce the size of the septum may also be used, and include surgical septal myectomy, and the use of alcohol to ablate the septum. Heart transplant is a last-line option.

Other cardiomyopathies

Restrictive cardiomyopathy

Restrictive cardiomyopathy (RCM) is a rare form of cardiomyopathy characterised by reduced myocardial compliance, leading to increased LV filling pressure, but with normal systolic function. It causes diastolic heart failure. Constrictive pericarditis is an important differential diagnosis. There is no specific treatment.

Arrhythmogenic right ventricular cardiomyopathy

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a rare form of cardiomyopathy characterised by thinning of the right ventricular wall, which predisposes to arrhythmias. An epsilon wave, a wave at the end of a widened QRS complex, is typical. Antiarrhythmic treatment and ICD implantation may be used.

Left ventricular non-compaction

Left ventricular non-compaction (LVNC) is a rare form of cardiomyopathy characterised by failure of intrauterine compaction of the myocardium, leading to a thickened endo-myocardium with trabeculae and deep recesses.

Takotsubo cardiomyopathy

Takotsubo cardiomyopathy, also referred to as Takotsubo syndrome, stress cardiomyopathy, and broken heart syndrome, is a form of cardiomyopathy characterised by transient hypo/dys/akinesia and ballooning of the apical segments of the left ventricle in response to severe stress, like a partner’s death.

It’s an acute condition which can cause severe heart failure, but it’s transient and usually completely reversible condition. It’s an important differential diagnosis in the evaluation of ACS. Echocardiography shows ballooning and reduced movement in the LV apex.