What is the best approach to evaluate a patient with dyspnea, considering their past medical history and potential respiratory or cardiac conditions?

Review of Systems for Dyspnea Evaluation

Begin by systematically eliciting the timing, quality, and associated symptoms of dyspnea, as these clinical descriptors directly guide diagnostic testing and narrow the differential diagnosis to specific cardiopulmonary pathologies. 1, 2, 3

Critical Historical Elements to Elicit

Timing and Pattern

• Duration: Determine if dyspnea is acute (<4 weeks) or chronic (>4-8 weeks), as this fundamentally changes the differential diagnosis 1, 3
• Onset: Sudden onset suggests pulmonary embolism or pneumothorax, while gradual progression indicates heart failure, COPD, or interstitial lung disease 2
• Exertional vs. rest: Dyspnea at rest indicates more severe disease with higher mortality risk 4
• Positional changes: Orthopnea and paroxysmal nocturnal dyspnea are highly specific for heart failure 2, 3

Quality of Dyspnea (Highly Discriminatory)

• "Chest tightness": Relatively specific for bronchoconstriction in asthma or COPD exacerbation 2, 3
• "Air hunger" or "inability to get a deep breath": Suggests restrictive mechanics from heart failure, pulmonary fibrosis, or dynamic hyperinflation 2, 3
• "Effort" or "suffocation": Nonspecific but may indicate panic disorder or hyperventilation syndrome 2, 3

Associated Cardiopulmonary Symptoms

• Cardiac: Chest pain (ischemia), palpitations (arrhythmias), lower extremity edema (heart failure), syncope (severe aortic stenosis or pulmonary hypertension) 2, 3
• Pulmonary: Cough (productive suggests pneumonia/COPD; dry suggests interstitial lung disease), wheezing (asthma/COPD), hemoptysis (pulmonary embolism, malignancy), pleuritic chest pain (pneumonia, pulmonary embolism, pneumothorax) 2, 3
• Constitutional: Fever (infection), weight loss (malignancy, heart failure), night sweats (tuberculosis, lymphoma) 2

Risk Factors and Past Medical History

• Smoking history: Quantify pack-years for COPD and lung cancer risk 2, 5
• Cardiac history: Prior myocardial infarction, heart failure, valvular disease, arrhythmias 2, 3
• Pulmonary history: Asthma, COPD, interstitial lung disease, prior pulmonary embolism 2, 3
• Occupational/environmental exposures: Asbestos, silica, organic dusts for interstitial lung disease 5
• Medication review: Beta-blockers (bronchospasm), amiodarone (pulmonary toxicity), chemotherapy (cardiomyopathy) 5
• Recent immobilization or surgery: Pulmonary embolism risk 2

Physical Examination Findings to Document

Vital Signs

• Tachypnea: >20 breaths/minute suggests respiratory distress 3
• Hypoxemia: SaO2 <90% indicates significant cardiopulmonary pathology 2
• Tachycardia: May indicate heart failure, pulmonary embolism, or anemia 3

Cardiovascular Examination

• Jugular venous distention: Elevated right atrial pressure from heart failure or pulmonary hypertension 2, 5
• S3 gallop: Highly specific for systolic heart failure 2
• Murmurs: Valvular disease (aortic stenosis, mitral regurgitation) 2
• Lower extremity edema: Bilateral suggests heart failure; unilateral suggests venous thrombosis 2, 3

Pulmonary Examination

• Decreased breath sounds: Pleural effusion, pneumothorax, or severe emphysema 2, 6
• Crackles: Bibasilar crackles suggest heart failure or interstitial lung disease; focal crackles suggest pneumonia 2, 3
• Wheezing: Asthma or COPD exacerbation 2
• Dullness to percussion: Pleural effusion or consolidation 2

Other Systems

• Clubbing: Interstitial lung disease, lung cancer, or cyanotic heart disease 5
• Cyanosis: Severe hypoxemia or right-to-left cardiac shunt 3
• Thyromegaly: Hyperthyroidism or hypothyroidism affecting cardiac function 2

Common Pitfalls to Avoid

• Do not rely on history and physical examination alone: Clinical assessment has high specificity (96%) but low sensitivity (59%) for cardiac causes—objective testing is mandatory 2
• Normal chest radiography does not exclude cardiac disease: Early heart failure and diastolic dysfunction may have normal chest X-rays 2
• Elderly patients may have diminished respiratory sensation: They may present with atypical symptoms or delayed breathlessness 3
• Consider multifactorial causes: More than 30% of chronic dyspnea cases have multiple contributing etiologies 1, 3
• Do not dismiss psychiatric causes prematurely: Panic disorder is a diagnosis of exclusion after cardiopulmonary pathology is ruled out 2, 3

Initial Diagnostic Testing Algorithm

After completing the review of systems, proceed immediately to first-line testing 1, 2:

1. Laboratory: Complete blood count (anemia, infection), basic metabolic panel (renal dysfunction, acidosis), BNP/NT-proBNP (BNP <100 pg/mL or NT-proBNP <125 pg/mL excludes heart failure) 2
2. Imaging: Chest radiography (pneumonia, heart failure, pleural effusion, pneumothorax, masses) 2
3. Cardiac: Electrocardiography (ischemia, arrhythmias, chamber enlargement) 2
4. Pulmonary: Spirometry (obstructive vs. restrictive patterns), pulse oximetry (hypoxemia) 2

If initial testing is nondiagnostic, proceed to second-line testing including echocardiography, pulmonary function tests, and chest CT 1, 2. Cardiopulmonary exercise testing is the definitive test for unexplained dyspnea when initial evaluations are nondiagnostic, as it categorizes abnormalities into oxygen delivery (cardiovascular), oxygen utilization (neuromuscular), or ventilatory disorders. 1