What laboratory tests are recommended for the evaluation of cardiomyopathy?

Laboratory Tests for Cardiomyopathy Evaluation

The comprehensive laboratory evaluation for cardiomyopathy should include complete blood count, urinalysis, serum electrolytes (including calcium and magnesium), glycohemoglobin, blood lipids, renal and hepatic function tests, thyroid function tests, and biomarkers such as BNP/NT-proBNP and troponin T. 1

Core Laboratory Tests for All Cardiomyopathy Patients

• Complete blood count: Anemia can exacerbate chest pain and dyspnea and should be excluded, especially when there is a change in symptoms 1
• Renal function tests: Renal function may be impaired in severe left ventricular dysfunction; impaired GFR and proteinuria may indicate amyloidosis, Anderson-Fabry disease, or mitochondrial disorders 1
• Serum electrolytes: Including calcium and magnesium to identify electrolyte abnormalities that may contribute to cardiac dysfunction 1
• Liver function tests: Liver transaminases may be abnormal in mitochondrial disorders, Danon disease, and β-oxidation defects 1
• Fasting glucose and glycohemoglobin: May be elevated in some mitochondrial DNA disorders or low in fatty acid and carnitine disorders 1
• Lipid profile: To assess cardiovascular risk factors 1
• Thyroid function tests: Both hyperthyroidism and hypothyroidism can be primary or contributory causes of heart failure 1
• Cardiac biomarkers: BNP/NT-proBNP and troponin T are associated with higher risk of cardiovascular events, heart failure, and death 1
• Creatine phosphokinase (CPK): Elevated in metabolic disorders such as Danon disease and mitochondrial disorders 1

Additional Specialized Testing Based on Clinical Suspicion

For Suspected Infiltrative Cardiomyopathy

• Serum immunoglobulin free light chain assay: Should be considered if amyloidosis is suspected 1
• Serum and urine electrophoresis: To detect paraproteins in suspected amyloidosis 1
• Plasma/leucocyte alpha-galactosidase A: Low or undetectable levels are present in male patients with Anderson-Fabry disease; should be considered in men aged >30 years 1
• Fasting transferrin saturation: Useful to screen for hemochromatosis, particularly in individuals of Northern European descent 1

For Suspected Metabolic or Mitochondrial Disorders

• Plasma lactate: Elevated in some patients with mitochondrial disorders 1
• Additional metabolic testing: May include pyruvate, ammonia, ketones, free fatty acids, carnitine profile, urine organic acids, and amino acids, particularly in pediatric cases 1

For Suspected Infectious Causes

• HIV screening: Reasonable in high-risk patients, though clinical signs of HIV infection typically precede heart failure symptoms 1
• Serum titers for infectious organisms: Occasionally measured in patients with recent onset of heart failure, especially following a viral syndrome, though yield is low 1

Genetic Testing Considerations

• Genetic testing: Should be considered in patients with suspected familial cardiomyopathy, with multigene panel testing now standard practice 1
• Yield of genetic testing: Varies by cardiomyopathy type (30-60% for HCM, 10-40% for DCM, 10-50% for ARVC) 1
• Family screening: First-degree relatives of patients with dilated cardiomyopathy should be considered for ECG and echocardiogram evaluation 1

Important Clinical Pitfalls to Avoid

• Don't overlook non-cardiac causes: Thyroid disease, renal dysfunction, and diabetes mellitus can cause or exacerbate ventricular dysfunction 1
• Consider specific disease markers: BNP values are typically three to five times higher in cardiac amyloidosis compared to other causes of HCM with similar wall thickness 1
• Don't rely solely on initial testing: Serial evaluations may be necessary as some genetic cardiomyopathies can manifest later in life 2
• Don't neglect family screening: Up to 30% of idiopathic dilated cardiomyopathy cases may be familial 1
• Consider bone scintigraphy: Particularly with 99mTc-DPD in patients with suspected TTR-related amyloidosis 1

By following this comprehensive laboratory evaluation approach, clinicians can identify underlying causes of cardiomyopathy, assess disease severity, and guide appropriate management strategies to improve patient outcomes.