What is the initial approach for a patient presenting with shortness of breath (SOB) on exertion?

Initial Approach to Shortness of Breath on Exertion

Begin with immediate vital signs including oxygen saturation, respiratory rate, pulse rate, blood pressure, and temperature, followed by focused history targeting cardiac versus pulmonary causes, then proceed to transthoracic echocardiography as the primary diagnostic test for suspected cardiac etiology. 1, 2

Immediate Clinical Assessment

Vital Signs and Initial Monitoring

• Measure oxygen saturation via pulse oximetry immediately in all patients presenting with breathlessness 1
• Record pulse rate, respiratory rate, blood pressure, and temperature as part of the ABC assessment 1, 2
• Continuous pulse oximetry monitoring should continue until the patient is stable 1

Critical History Elements

Cardiac-specific symptoms to elicit:

• Orthopnea is a hallmark symptom indicating elevated pulmonary capillary pressure and pulmonary edema 3
• Paroxysmal nocturnal dyspnea suggests left ventricular dysfunction 1
• Peripheral edema indicates heart failure 1
• History of ischemic heart disease, diabetes mellitus, and hypertension represents high-risk profile for heart failure 3
• In elderly patients with established ischemic heart disease, dyspnea frequently substitutes for typical anginal symptoms 3

Pulmonary-specific symptoms:

• Chronic breathlessness on minor exertion (such as walking on level ground) in patients >50 years who are long-term smokers suggests COPD 1
• Wheezing during vigorous exercise may indicate exercise-induced bronchoconstriction 1, 2

High-risk features requiring immediate exclusion:

• Recent venous procedures or history of venous insufficiency raises concern for pulmonary embolism 2
• Massive hemoptysis with dyspnea requires urgent evaluation for pulmonary vascular pathology 4

Initial Laboratory Testing

Essential blood work:

• Complete blood count to exclude anemia as a cause 5
• Basic metabolic panel 5
• Brain natriuretic peptide (BNP) levels to help exclude heart failure 3, 5
• D-dimer testing if pulmonary embolism is suspected 2, 5
• Transferrin saturation >55% may indicate iron overload cardiomyopathy in appropriate clinical context 1

Initial Imaging Studies

Chest Radiography

• Obtain chest X-ray in all patients with dyspnea to assess for pulmonary edema, cardiomegaly, or pulmonary pathology 3, 5

Electrocardiography

• Perform ECG to identify arrhythmias, ischemia, or conduction abnormalities 1, 5

Transthoracic Echocardiography (Primary Cardiac Diagnostic Test)

TTE is mandated as the primary imaging modality when cardiac cause is suspected: 1

For suspected heart failure:

• Early TTE is mandated in all patients with suspected heart failure to confirm or exclude diagnosis, quantify chamber volumes, assess systolic and diastolic function, and identify etiology 1
• TTE identifies heart failure with preserved, mid-range, or reduced ejection fraction 1

For suspected valvular disease:

• TTE is the primary imaging modality for diagnosis and assessment of severity when SOB with suspected valvular heart disease based on history or examination (e.g., systolic murmur) 1

For suspected cardiomyopathy:

• TTE is fundamental for diagnosis and classification of hypertrophic, dilated, arrhythmogenic, or restrictive cardiomyopathies 1

TTE assessment should focus on:

• LV size, wall thickness, and systolic/diastolic function 1
• RV size and function 1
• Valve structure and function 1
• Pericardium 1

Spirometry

• Perform spirometry as part of initial testing to identify obstructive or restrictive lung disease 5
• Measure FEV1 unless patient is too breathless to perform test 1

Advanced Diagnostic Testing When Diagnosis Remains Unclear

Cardiopulmonary Exercise Testing (CPET)

CPET is the definitive test to distinguish between cardiac, pulmonary, vascular, and deconditioning causes when initial evaluation is inconclusive: 1, 2

Key CPET parameters:

• Peak VO2 (percent-predicted) to assess functional capacity 1
• VE/VCO2 slope and PETCO2 to identify ventilation-perfusion abnormalities suggesting pulmonary vasculopathy 1
• Peak exercise VE/MVV ratio to assess ventilatory limitation 1
• O2 pulse and heart rate-VO2 relationship for cardiac dysfunction 2
• SpO2 monitoring throughout exercise and recovery 1

Post-exercise spirometry:

• Measure FEV1 and peak expiratory flow at 1,3,5,7,10,15, and 20 minutes post-exercise 1
• Decrease in FEV1 >15% post-exercise suggests exercise-induced bronchoconstriction 1

CT Chest

• CT chest is the most appropriate imaging study for diagnosing suspected pulmonary causes when chest X-ray is nondiagnostic 5

Common Pitfalls to Avoid

Oxygen administration errors:

• In patients with COPD or risk factors for hypercapnic respiratory failure (age >50, long-term smoker, chronic breathlessness), target oxygen saturation of 88-92% rather than normal saturation 1
• Excessive oxygen therapy (PO2 >10 kPa or 75 mmHg) in COPD patients causes CO2 retention and respiratory acidosis 1
• If respiratory acidosis develops from excessive oxygen, step down to 28% or 35% Venturi mask or 1-2 L/min nasal cannula rather than discontinuing oxygen abruptly 1

Diagnostic errors:

• Do not assume asthma in patients >50 years with smoking history and chronic exertional breathlessness—treat as suspected COPD 1
• Chronic venous insufficiency is a noncardiac mimic of heart failure with preserved ejection fraction, making this differential particularly challenging 2
• Clinical presentation alone is adequate for diagnosis in only 66% of patients; one-third have multifactorial etiology requiring comprehensive testing 5