Overview

Hypertrophic cardiomyopathy (HCM) is a cardiac condition defined as ‘unexplained’ left ventricular hypertrophy (LVH) in the absence of abnormal loading conditions (for example, hypertension).¹ A diagnosis of HCM has significant implications as HCM can lead to heart failure, stroke, or sudden cardiac death.

The condition is usually inherited in an autosomal-dominant manner; however, there are numerous genetic variants that lead to disorganised myocyte architecture and subsequent ventricular hypertrophy.¹ While HCM is often diagnosed because of clinical suspicion based on symptoms (which can include difficulty breathing), it can also be identified coincidentally or through family screening.

This module provides a broad overview of this rare — but increasingly-identified — condition, focusing on how to reduce the risk of mortality and morbidity.

HCM is usually inherited in an autosomal-dominant
manner

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Reference
1. Elliott PM, Anastasakis A, Borger MA et al. 2014 ESC Guidelines on diagnosis and management of hypertrophic cardiomyopathy: the Task Force for the Diagnosis and Management of Hypertrophic Cardiomyopathy of the European Society of Cardiology (ESC). Eur Heart J 2014; 35(39): 2733–79.

Probands

The term ‘proband’ refers to the first-identified affected member in a family, and these individuals can provide the opportunity to identify affected relatives.

Genetic testing can often be performed in probands to identify a variant that has caused the clinical phenotype. Once identified, predictive testing of other family members can be performed to identify those at risk of the clinical syndrome.⁴ It can also help with prognostication as data from the Sarcomeric Human Cardiomyopathy Registry (SHaRe) demonstrate genotype-positive HCM is associated with earlier onset of disease and greater morbidity.⁵

References
4 Lorenzini M, Norrish G, Field E et al. Penetrance of Hypertrophic Cardiomyopathy in sarcomere protein mutation carriers. J Am Coll Cardiol 2020; 76(5): 550–9.
5. Ho CY, Day SM, Ashley EA et al. Genotype and lifetime burden of disease in hypertrophic cardiomyopathy: insights from the sarcomeric human cardiomyopathy registry (SHaRe). Circulation 2018; 138(14): 1387–98.

Signs and symptoms

HCM is often diagnosed in the outpatient setting with common presentations including:

● Difficulty in breathing
● Exercise intolerance
● Chest pain
● Palpitations

LVOT obstruction
Symptoms can also be a result of left ventricular outflow tract (LVOT) obstruction — hypertrophic obstructive cardiomyopathy (HOCM) — because of a narrowing of the outflow tract and mitral valve abnormalities. LVOT obstruction is present in around 33% of people with HCM at rest and in around 60–70% with exercise provocation. Syncope on exertion can also relate to LVOT obstruction. If there is LVOT obstruction, clinical examination may uncover a systolic murmur that is exaggerated on Valsalva manoeuvre and diminished with squatting.

Arrhythmias
On palpation of the precordium, a displaced and forceful apex beat may present. The most common arrhythmia associated with HCM is atrial fibrillation (AF), which presents with an irregular rhythm and can be seen in up to 20% of patients with HCM by the sixth decade of life.

Congenital or metabolic problems causing LVH identified as HCM are often present in infancy, whereas amyloidosis is more likely to present in later life.

A detailed family history is important to help identify the mode of inheritance, and a history of unexplained sudden death should be explored further.

ECG

Simple investigations include an ECG, which will be abnormal in 80–90% of people with HCM and show voltage criteria for LVH or ST-segment/T-wave abnormalities.

Ambulatory ECG monitoring can identify paroxysmal arrhythmias, including AF or non-sustained ventricular tachycardia (an important part of risk stratification for sudden cardiac death).

Ambulatory ECG monitoring can identify
paroxysmal arrhythmias, including AF or
non-sustained ventricular tachycardia

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