What lab work would you order for a patient with worsening fatigue and a history of congestive heart failure?

Laboratory Work for a Patient with Worsening Fatigue and History of Congestive Heart Failure

For a patient with worsening fatigue and a history of congestive heart failure, the initial laboratory evaluation should include complete blood count, urinalysis, serum electrolytes (including calcium and magnesium), blood urea nitrogen, serum creatinine, fasting blood glucose (glycohemoglobin), lipid profile, liver function tests, and thyroid-stimulating hormone. 1

Core Laboratory Tests

The following laboratory tests are essential for evaluating a patient with worsening heart failure:

1. Complete Blood Count (CBC)

   • Identifies anemia (present in 1/3 to 1/2 of CHF cases) 2
   • Detects infections that may exacerbate heart failure
   • Evaluates white blood cell count for inflammatory processes

2. Basic Metabolic Panel

   • Serum electrolytes (sodium, potassium, chloride, bicarbonate)
   • Calcium and magnesium (abnormalities can affect cardiac function)
   • Blood urea nitrogen (BUN) and creatinine (assess kidney function)
   • Glucose (diabetes is a comorbidity and risk factor)

3. Liver Function Tests

   • Evaluates hepatic congestion from right-sided heart failure
   • AST, ALT, bilirubin, and albumin

4. Thyroid-Stimulating Hormone (TSH)

   • Thyroid dysfunction can worsen or mimic heart failure symptoms

5. Lipid Profile

   • Evaluates cardiovascular risk factors
   • Guides statin therapy decisions

6. Urinalysis

   • Screens for proteinuria (indicating kidney damage)
   • Evaluates for urinary tract infection

Additional Important Tests

1. Natriuretic Peptides

   • BNP or NT-proBNP measurement is strongly recommended
   • Helpful for risk stratification and diagnosis confirmation
   • Particularly useful when clinical diagnosis is uncertain 1

2. Cardiac Biomarkers

   • Troponin to rule out acute myocardial injury
   • Especially important if symptoms worsened acutely

Specialized Tests Based on Clinical Suspicion

For selected patients with specific clinical presentations, consider:

• Hemochromatosis screening (if suspected iron overload)
• HIV testing (if risk factors present)
• Rheumatologic disease markers (if symptoms suggest autoimmune etiology)
• Amyloidosis testing (if unexplained thickened ventricular walls)
• Pheochromocytoma screening (if labile hypertension) 1

Imaging and Other Non-Laboratory Tests

While not laboratory tests, these are essential components of the evaluation:

• 12-lead ECG (to assess for arrhythmias, ischemia, or conduction abnormalities)
• Chest radiograph (PA and lateral views to assess for cardiomegaly and pulmonary congestion)
• Echocardiography (to assess ejection fraction, ventricular size, and valve function)

Common Pitfalls to Avoid

• Overlooking anemia: Anemia can worsen heart failure symptoms and is often undertreated 2
• Neglecting kidney function: Heart failure and kidney disease form a vicious cycle, each worsening the other 2
• Missing thyroid dysfunction: Can mimic or exacerbate heart failure symptoms
• Ignoring electrolyte abnormalities: Particularly important in patients on diuretics
• Failing to measure natriuretic peptides: Provides valuable diagnostic and prognostic information

By systematically ordering these laboratory tests, you can comprehensively evaluate the patient's worsening fatigue in the context of their heart failure history, identify potential exacerbating factors, and guide appropriate management decisions.