What labs would you order for a new patient with a history of dilated cardiomyopathy, arrhythmia, moderate mitral insufficiency, Biventricular Implantable Cardioverter-Defibrillator (ICD) in place, chronic systolic congestive heart failure (CHF) New York Heart Association (NYHA) class 2, coronary artery disease (CAD), hypertension (HTN), idiopathic dizziness, and ischemic cardiomyopathy?

Laboratory Tests for a New Patient with Dilated Cardiomyopathy and Multiple Cardiac Conditions

For a new patient with dilated cardiomyopathy, arrhythmia, moderate mitral insufficiency, biventricular ICD, chronic systolic CHF (NYHA class 2), CAD, hypertension, idiopathic dizziness, and ischemic cardiomyopathy, a comprehensive laboratory evaluation should include complete blood count, urinalysis, serum electrolytes, renal and liver function tests, lipid profile, glucose/HbA1c, thyroid function, natriuretic peptides, and cardiac biomarkers. 1

Core Laboratory Tests

• Complete blood count (CBC) to identify anemia which can exacerbate heart failure symptoms and chest pain 1, 2
• Urinalysis to detect proteinuria or renal abnormalities that may contribute to fluid retention 1, 2
• Serum electrolytes including sodium, potassium, calcium, and magnesium to identify imbalances that may affect cardiac function or be caused by diuretic therapy 1
• Blood urea nitrogen (BUN) and serum creatinine to assess renal function, which is crucial for medication management and prognosis 1
• Liver function tests (bilirubin, AST, ALT, GGTP) to evaluate hepatic congestion and assess for underlying liver disease 1
• Fasting blood glucose and glycohemoglobin (HbA1c) to identify diabetes, which is both a risk factor and comorbidity in heart failure 1
• Lipid profile to assess cardiovascular risk factors and guide statin therapy for CAD 1
• Thyroid-stimulating hormone (TSH) to rule out thyroid disorders that can cause or exacerbate heart failure 1

Cardiac-Specific Biomarkers

• B-type natriuretic peptide (BNP) or N-terminal pro-BNP (NT-proBNP) to:
  • Establish disease severity and prognosis 1, 2
  • Support clinical decision-making regarding diagnosis 1
  • Guide medication titration 1, 2
• Cardiac troponin levels to assess for ongoing myocardial injury and risk stratification 1, 2

Additional Tests Based on Clinical Context

• Iron studies (serum iron, ferritin, transferrin saturation) to identify iron deficiency, which is common in heart failure and impacts symptoms 1, 2
• Fasting transferrin saturation to screen for hemochromatosis, especially in patients of Northern European descent 1
• Screening for HIV in high-risk patients, as it can cause cardiomyopathy 1

Tests for Specific Etiologies

• For patients with dilated cardiomyopathy without clear etiology, consider:
  • Tests for rheumatologic diseases if clinically suspected 1
  • Tests for amyloidosis if clinically suspected 1
  • Tests for pheochromocytoma if clinically suspected 1
  • Serum titers for Chagas disease antibodies in patients who have traveled to or immigrated from endemic regions 1

Non-Laboratory Tests to Consider

• 12-lead electrocardiogram to assess rhythm, conduction abnormalities, and evidence of ischemia 1
• Chest radiograph (posterior-anterior and lateral) to assess heart size and pulmonary congestion 1
• Echocardiography to reassess ventricular function, especially if clinical status has changed 1

Important Considerations and Pitfalls

• Renal function and electrolytes should be monitored regularly, especially after medication adjustments (ACE inhibitors, ARBs, diuretics, aldosterone antagonists) 1, 2
• BNP/NT-proBNP levels can be affected by:
  • Age (higher in elderly)
  • Renal dysfunction (falsely elevated)
  • Obesity (falsely low) 2
• In patients with biventricular ICD, monitor electrolytes closely as imbalances can trigger arrhythmias 1, 2
• For patients with idiopathic dizziness, consider additional testing for potential cardiac causes (e.g., arrhythmias) or non-cardiac causes (e.g., vestibular disorders) 1
• Patients with ischemic cardiomyopathy may have different laboratory profiles compared to those with idiopathic dilated cardiomyopathy, including higher rates of renal dysfunction and fasting hyperglycemia 3

Remember that laboratory testing is just one component of the evaluation, and findings should be interpreted in the context of the patient's clinical presentation and imaging results.