Diagnostic Criteria for Hypertrophic Cardiomyopathy

Primary Diagnostic Threshold

The American College of Cardiology recommends a maximal end-diastolic LV wall thickness of ≥15 mm anywhere in the left ventricle in adults, measured by 2D echocardiography or cardiovascular magnetic resonance imaging, for the diagnosis of Hypertrophic Cardiomyopathy (HCM) 1, 2
The American Heart Association suggests that a wall thickness of 13-14 mm can establish the diagnosis when the patient is a first-degree family member of someone with confirmed HCM or when a pathogenic or likely pathogenic sarcomere gene variant has been identified 1, 2, 3

The American College of Cardiology recommends ruling out other causes of LV hypertrophy, such as long-standing systemic hypertension, aortic stenosis, infiltrative diseases, storage diseases, athletic remodeling, and RAS-MAPK signaling disorders, before diagnosing HCM 1, 2, 3, 4

The American Heart Association notes that basal anterior septum and anterior free wall hypertrophy is the most common pattern seen in HCM, and that focal or segmental hypertrophy limited to 1-2 LV segments can also be present 1, 2
Apical hypertrophy, best detected by CMR with contrast, can also be a feature of HCM 4, 5

The American College of Cardiology states that systolic anterior motion (SAM) of the mitral valve, hyperdynamic LV function, hypertrophied and apically displaced papillary muscles, myocardial crypts, elongated mitral valve leaflets, myocardial bridging, and right ventricular hypertrophy are features that support but do not confirm HCM 1, 2

The American Heart Association recommends transthoracic echocardiography as the first-line imaging test for suspected HCM, and CMR imaging when echocardiography is inconclusive or when apical hypertrophy or apical aneurysm is suspected 5, 6
CMR with late gadolinium enhancement can identify myocardial fibrosis, which is common in HCM but not required for diagnosis 4, 8, 9

The American College of Cardiology notes that approximately 30-60% of HCM patients have an identifiable pathogenic sarcomere gene variant, most commonly in MYH7 or MYBPC3, and that genotype-positive individuals without LV hypertrophy should be considered "at risk" but do not yet have clinically evident HCM 1

The American Heart Association warns against diagnosing HCM in the presence of adequate alternative explanations for hypertrophy, missing apical HCM by relying solely on echocardiography without CMR, assuming SAM or LVOT obstruction is required for diagnosis, and concluding HCM is absent in young family members with normal studies 1, 2, 3, 5, 6