7th March 2024

Background

Cardiomyopathies are heart muscle disorders with abnormalities of either systolic or diastolic function in which there is a primary abnormality of the heart muscle itself i.e., in the absence of coronary artery disease, hypertension, valvular heart disease or congenital heart disease. These disorders can be due to changes in the nature of the underlying intracellular make-up, deposition of pathological material in the intercellular space or abnormal function of cardiac muscle. 

The subclassification of cardiomyopathies remains an evolving field as we understand more about their pathologies, but a standard classification would include:

• Dilated Cardiomyopathy (DCM)
• Hypertrophic cardiomyopathy (HCM)
• Restrictive Cardiomyopathy (RCM)
• Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC)
• Unclassified – including Takotsubo cardiomyopathy and Left Ventricular non-compaction

Once classified as above, the cardiomyopathies can be subclassified as familial/genetic vs non-familial/non-genetic/acquired.

There is still ongoing discussion about these terms, particularly as some hypertrophic conditions can lead to restrictive physiology, which can lead to confusion regarding nomenclature. 

Symptomatology is largely related to the effect that the underlying pathology has on cardiac function. Conditions in which the underlying pathology is acquired as part of a multi-system disorder (such as HCM in the context of Friedrich’s ataxia) are likely to display a much wider range of symptoms, whilst those with intrinsic cardiac disease will show signs and symptoms purely of cardiac dysfunction related to the exact effect that the pathology has on the function heart.

All patients with a suspected cardiomyopathy should initially be investigated with:

• A full and thorough history with a focus on family history to elucidate any potentially inherited conditions. Specific questions should be asked about any history of sudden death or epilepsy in the family – often a misdiagnosis in the context of cardiogenic syncope
• Basic observations including temperature, heart rate, blood pressure, respiratory rate and oxygen saturation
• Blood tests including full blood count, renal function, liver function tests, NT pro-BNP, troponin, bone profile, cholesterol and HbA1C
• 12-lead ECG – at least 2 if the symptoms are acute to help rule out dynamic ECG changes
• Echocardiogram

Natriuretic peptides (BNP and NT-pro BNP) will be elevated almost without fail in cases with overt heart failure, as the release of these biomarkers is caused by elevations of intraventricular pressure.

There are some additional investigations pertinent to the individual classes of cardiomyopathy which will be discussed in the relevant sections.

Treatment will be related to either amelioration of the underlying disease process, treatment of impaired cardiac function, or aimed at prevention of further deleterious sequelae caused by the disease such as arrhythmia causing haemodynamic instability or sudden cardiac death.