What blood tests are ordered for Hypertrophic Cardiomyopathy (HCM)?

Blood Tests for Hypertrophic Cardiomyopathy (HCM)

Laboratory testing in HCM should focus on excluding phenocopies and secondary causes of left ventricular hypertrophy, as there is no specific blood test that diagnoses sarcomeric HCM. 1

Core Laboratory Tests for HCM Evaluation

Initial Diagnostic Workup

• Complete Blood Count

  • Hemoglobin (to exclude anemia) 1

• Basic Metabolic Panel

  • Renal function tests (BUN, creatinine) 1
  • Electrolytes
  • Fasting glucose (to exclude diabetes) 1

• Liver Function Tests

  • Liver transaminases (to exclude liver disease) 1

• Cardiac Biomarkers

  • Brain natriuretic peptide (BNP) 1
  • Troponin T 1

• Endocrine Testing

  • Thyroid function tests (TSH, free T4) 1

Specific Tests to Rule Out HCM Phenocopies

• Storage/Infiltrative Disease Testing

  • Alpha-galactosidase A enzyme level (to exclude Fabry disease) 1, 2
  • Immunoglobulin free light chain assay (to exclude amyloidosis) 1

• Muscle Disease Testing

  • Creatine phosphokinase (CPK) (to exclude muscle disease) 1

Additional Testing Based on Clinical Suspicion

• For Suspected Metabolic/Storage Disorders

  • Urine protein electrophoresis
  • Serum protein electrophoresis
  • Serum free light chains (if amyloidosis suspected)
  • Lysosomal enzyme testing (for storage diseases)

• For Suspected Mitochondrial Disorders

  • Lactate levels
  • Pyruvate levels

Genetic Testing Considerations

• Genetic testing is recommended for patients with confirmed HCM to enable cascade genetic screening of relatives 3

• Genetic testing should target:

  • Sarcomeric protein genes (MYBPC3, MYH7 most common) 4
  • Other genetic causes based on clinical suspicion 3

• Pre- and post-test genetic counseling by cardiovascular genetics experts is essential 3

Testing Algorithm

1. Initial Evaluation:

   • Complete standard laboratory panel (CBC, metabolic panel, liver function, cardiac biomarkers, thyroid function)

2. Secondary Evaluation:

   • If clinical features suggest specific phenocopies, order targeted tests:
     • For infiltrative disease: Alpha-galactosidase A, immunoglobulin free light chains
     • For muscle disease: CPK
     • For metabolic disorders: Additional metabolic workup

3. Genetic Evaluation:

   • Consider genetic testing for confirmed HCM cases
   • Ensure genetic counseling before and after testing

Important Considerations

• Blood tests primarily help exclude secondary causes rather than confirm HCM diagnosis 3, 1

• No single blood test can diagnose sarcomeric HCM - diagnosis relies primarily on imaging (echocardiography, cardiac MRI) showing increased left ventricular wall thickness ≥15 mm in adults 3

• Laboratory testing should be interpreted in context with imaging findings, family history, and clinical presentation 1

• Pitfall to avoid: Failing to consider phenocopies that may require specific treatment (e.g., Fabry disease, amyloidosis) 1, 2

• Regular monitoring: Consider periodic assessment of cardiac biomarkers (BNP, troponin) to evaluate disease progression 1