What are the diagnostic criteria for Hypertrophic Obstructive Cardiomyopathy (HOCM)?

From the Guidelines

Diagnosis of HOCM should be established by imaging, typically with 2D echocardiography or cardiovascular magnetic resonance (CMR), showing a maximal end-diastolic wall thickness of ≥15 mm anywhere in the left ventricle, in the absence of another cause of hypertrophy in adults, as recommended by the 2024 AHA/ACC/AMSSM/HRS/PACES/SCMR guideline 1.

Diagnostic Criteria

The clinical definition of HCM is considered a disease state in which morphologic expression is confined solely to the heart, characterized predominantly by left ventricular hypertrophy (LVH) in the absence of another cardiac, systemic, or metabolic disease capable of producing the magnitude of hypertrophy evident in a given patient 1.

• A maximal end-diastolic wall thickness of ≥15 mm anywhere in the left ventricle is diagnostic of HCM in adults.
• More limited hypertrophy (13-14 mm) can be diagnostic when present in family members of a patient with HCM or in conjunction with a positive genetic test identifying a pathogenic or likely pathogenic variant often in a sarcomere gene.
• For children, the diagnostic criteria are confounded by needing to adjust for body size and growth, and a body surface area adjusted z-score of ≥2 standard deviations above the mean has been used, but a threshold of a z-score >2.5 may be appropriate to identify early HCM in asymptomatic children with no family history.

Imaging and Diagnostic Tools

• 2D echocardiography or cardiovascular magnetic resonance (CMR) are the preferred imaging modalities for diagnosing HCM.
• Echocardiography can show asymmetric septal hypertrophy, systolic anterior motion of the mitral valve, and left ventricular outflow tract obstruction.
• Cardiac MRI provides additional structural details and can detect myocardial fibrosis using late gadolinium enhancement.

Genetic Testing and Family Screening

• Genetic testing is valuable for confirming the diagnosis and screening family members, as HOCM is often inherited in an autosomal dominant pattern with mutations commonly found in sarcomeric proteins.
• Family screening is essential since first-degree relatives have a 50% risk of inheriting the condition, and early detection can guide management strategies to prevent sudden cardiac death 1.

From the Research

Diagnosis of HOCM

The diagnosis of Hypertrophic Obstructive Cardiomyopathy (HOCM) involves several steps, including:

• History-taking and physical examination 2
• Genetic studies 2
• Transthoracic echocardiography 2, 3, 4
• Cardiac MRI 2, 3, 4
• Electrocardiogram (ECG) 5 The diagnosis is usually suspected on clinical examination and confirmed by imaging 6.

Imaging Techniques

Imaging techniques play a crucial role in the diagnosis and management of HOCM, including:

• Resting and stress imaging to provide comprehensive and complementary information 3
• Advanced imaging to guide certain treatment options, such as septal reduction therapy and mitral valve repair 3
• 3D reconstruction in echocardiography and CMR for more accurate morphological and volumetric assessment of the left ventricle 4
• Tissue characterization and scar burden quantification by late gadolinium enhancement on CMR to understand fibrotic processes in HOCM 4

Role of ECG

The ECG remains an essential tool in the diagnosis and management of HOCM, including:

• Early identification of the disease 5
• Differential diagnosis from phenocopies such as cardiac amyloidosis and glycogen storage diseases 5
• Risk stratification and development of targeted therapies 5
• Various clinical settings where its appropriate use and interpretation can make a difference 5