What is the diagnostic workup for a patient with orthopnea (shortness of breath when laying down)?

Diagnostic Workup for Orthopnea (Shortness of Breath When Lying Down)

The diagnostic workup for orthopnea should begin with cardiac evaluation, particularly focusing on heart failure, as this is the most common cause of positional dyspnea when lying flat.

Initial Assessment

• Evaluate for specific symptoms associated with orthopnea, including:

  • Number of pillows needed to sleep comfortably (pillow orthopnea)
  • Presence of paroxysmal nocturnal dyspnea (waking up gasping for air)
  • Peripheral edema, especially in lower extremities
  • Fatigue and exercise intolerance 1

• Physical examination should focus on:

  • Vital signs including blood pressure and heart rate
  • Jugular venous distention
  • Pulmonary rales/crackles
  • S3 heart sound (indicates ventricular dysfunction)
  • Peripheral edema 1

First-Line Diagnostic Tests

• Chest X-ray - Essential component to detect:

  • Cardiomegaly
  • Pulmonary venous congestion
  • Interstitial edema
  • Pleural effusions
  • Upper lobe venous diversion 1

• 12-lead ECG - To evaluate for:

  • Cardiac rhythm abnormalities
  • Evidence of prior myocardial infarction
  • Left ventricular hypertrophy
  • Note: A completely normal ECG makes heart failure with systolic dysfunction unlikely (<10%) 1

• Laboratory tests:

  • Complete blood count (to assess for anemia)
  • Basic metabolic panel (electrolytes, renal function)
  • Natriuretic peptides:
    • BNP < 100 pg/mL or NT-proBNP < 300 pg/mL: heart failure unlikely
    • BNP > 400 pg/mL or NT-proBNP > 2000 pg/mL: heart failure likely
    • Intermediate values require additional testing 1

Second-Line Diagnostic Tests

• Echocardiography - Most useful method for evaluating:

  • Left ventricular systolic function (ejection fraction)
  • Diastolic dysfunction
  • Valvular abnormalities
  • Restrictive mitral pattern (sensitivity 89%, specificity 93% for heart failure) 1

• Point-of-care ultrasonography (POCUS) - Can improve diagnostic accuracy when added to standard evaluation:

  • Allows immediate bedside assessment
  • Can detect pleural effusions, pulmonary congestion, and cardiac abnormalities
  • Improves correctness of diagnosis in patients with acute dyspnea 1

• CT chest - Consider when:

  • Chest X-ray is inconclusive
  • Pulmonary causes need further evaluation
  • Pulmonary embolism is suspected 1

• Pulmonary function tests - If respiratory causes are suspected:

  • Spirometry to evaluate for obstructive or restrictive patterns
  • Diffusion capacity studies 1, 2

Specialized Testing Based on Clinical Suspicion

• For suspected cardiac causes:

  • Stress echocardiography - If ischemia is suspected
  • Cardiac MRI - For myocardial characterization when cardiomyopathy is suspected
  • Coronary CT angiography - To evaluate coronary artery disease 1

• For suspected pulmonary vascular disease:

  • CT pulmonary angiography - To evaluate for pulmonary embolism
  • Right heart catheterization - Gold standard for diagnosing pulmonary hypertension 1

Algorithm for Orthopnea Evaluation

1. Initial evaluation: History, physical exam, chest X-ray, ECG, and natriuretic peptide testing 1

2. If natriuretic peptides elevated or chest X-ray shows congestion:

   • Proceed to echocardiography to confirm heart failure and characterize type (systolic vs. diastolic) 1

3. If initial cardiac evaluation is negative:

   • Consider pulmonary causes with CT chest and pulmonary function testing 1

4. If both cardiac and primary pulmonary causes are ruled out:

   • Consider less common causes:
     • Diaphragmatic dysfunction
     • Neuromuscular disorders
     • Obesity hypoventilation syndrome
     • Hepatopulmonary syndrome 3, 4

Common Pitfalls to Avoid

• Failing to recognize multifactorial causes - Up to one-third of dyspnea cases have multiple contributing factors 1

• Overlooking non-cardiac causes - While heart failure is the most common cause of orthopnea, other conditions can present similarly 5

• Relying solely on natriuretic peptides - BNP/NT-proBNP may be less reliable in:

  • Obesity (falsely low values)
  • Renal dysfunction (falsely elevated)
  • Acute settings (may lag behind clinical presentation) 1

• Missing valvular heart disease - Careful auscultation and echocardiography are essential to detect valvular causes of orthopnea 1