Is there an indication of hypertrophic cardiomyopathy (HCM) in this case?

Diagnostic Criteria for Hypertrophic Cardiomyopathy

To determine if HCM is present, you need imaging evidence of left ventricular wall thickness ≥15 mm in any segment on echocardiography or CMR, in the absence of another cause of hypertrophy (such as hypertension, aortic stenosis, or infiltrative disease). 1

Primary Diagnostic Threshold

The diagnosis requires 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. 1

Lower Diagnostic Thresholds in Specific Contexts

• Wall thickness of 13-14 mm can establish the diagnosis when:

  • The patient is a first-degree family member of someone with confirmed HCM 1
  • A pathogenic or likely pathogenic sarcomere gene variant has been identified 1

• In children, use body surface area-adjusted z-scores: 1

  • Z-score >2.5 for asymptomatic children without family history
  • Z-score >2 for children with definitive family history or positive genetic testing

Essential Exclusion Criteria

You must rule out other causes of LV hypertrophy before diagnosing HCM: 1

• Long-standing systemic hypertension (hypertensive cardiomyopathy)
• Aortic stenosis or other left-sided obstructive lesions
• Infiltrative diseases: cardiac amyloidosis, Fabry disease, Danon cardiomyopathy 1
• Storage diseases: glycogen and lysosomal storage diseases 1
• Athletic remodeling ("athlete's heart") 1
• RAS-MAPK signaling disorders (Noonan syndrome, LEOPARD syndrome) 1

Morphologic Patterns Supporting HCM Diagnosis

While not required for diagnosis, these features are commonly seen in HCM: 1

• Basal anterior septum and anterior free wall hypertrophy (most common pattern) 1
• Asymmetric septal hypertrophy 2
• Focal or segmental hypertrophy limited to 1-2 LV segments 1
• Apical hypertrophy (best detected by CMR with contrast) 1

Features That Support But Don't Confirm HCM

These findings are part of the phenotypic expression but are NOT diagnostic or required: 1

• Systolic anterior motion (SAM) of the mitral valve 1
• Hyperdynamic LV function 1
• Hypertrophied and apically displaced papillary muscles 1
• Myocardial crypts 1
• Elongated mitral valve leaflets 1
• Myocardial bridging 1
• Right ventricular hypertrophy 1

Imaging Modalities for Diagnosis

Transthoracic echocardiography is the first-line imaging test for suspected HCM. 1

CMR imaging is indicated when: 1

• Echocardiography is inconclusive for diagnosis 1
• Apical hypertrophy or apical aneurysm is suspected 1, 3
• Precise characterization of hypertrophy distribution is needed for treatment planning 1
• Differentiation from infiltrative diseases is required 1

CMR with late gadolinium enhancement identifies myocardial fibrosis, which is common in HCM but not required for diagnosis. 1

Genetic Considerations

Approximately 30-60% of HCM patients have an identifiable pathogenic sarcomere gene variant, most commonly in MYH7 or MYBPC3. 1

Important caveats: 1

• Genotype-positive individuals without LV hypertrophy should be considered "at risk" but do not yet have clinically evident HCM
• Up to 40% of patients have no identifiable genetic cause or affected family members ("nonfamilial" HCM)
• Normal wall thickness does not exclude future development of HCM in genetically affected individuals

Common Diagnostic Pitfalls

Avoid these errors: 1

• Diagnosing HCM in the presence of adequate alternative explanations for hypertrophy (hypertension, aortic stenosis)
• Missing apical HCM by relying solely on echocardiography without CMR 1
• Assuming SAM or LVOT obstruction is required for diagnosis 1
• Concluding HCM is absent in young family members with normal studies, as late-onset hypertrophy can occur well into adulthood 4