Most Appropriate Investigation
The most appropriate initial investigation is B) ECHO (echocardiography). This patient presents with a classic constellation of heart failure symptoms—orthopnea, bilateral lower extremity edema, nocturia, hypertension, and hypoxemia with clear lung fields—which mandates immediate cardiac assessment 1.
Clinical Reasoning
Why ECHO is the Priority
Orthopnea is a classic symptom of left ventricular dysfunction and elevated pulmonary capillary wedge pressure, and the American Heart Association recommends obtaining ECHO immediately to assess ventricular function, valvular disease, and pulmonary pressures in patients with suspected heart failure 1.
Hypoxemia (O2 sat 87%) with clear lungs strongly suggests cardiac rather than primary pulmonary pathology, as this pattern indicates impaired cardiac output and pulmonary vascular congestion without alveolar infiltrates 1.
The combination of bilateral lower extremity edema, orthopnea, nocturia, and hypertension represents the classic tetrad of congestive heart failure requiring urgent echocardiographic evaluation 1.
Why Other Options Are Inappropriate Initially
Sleep Study (Option A):
- While obstructive sleep apnea (OSA) can coexist with heart failure and cause bilateral leg edema 2, 3, 4, the American Heart Association advises not to assume nocturia is purely urological and to consider sleep study only after cardiac status is clarified and stabilized 1.
- The acute hypoxemia and orthopnea suggest decompensated heart failure requiring immediate cardiac assessment before pursuing sleep disorder evaluation 1.
Chest CT (Option C):
- The European Respiratory Society states that CT has no role in the initial workup of suspected heart failure 1.
- The clinical presentation points to cardiac pathology, not parenchymal lung disease requiring CT characterization 1.
Chest X-ray (Option D):
- While CXR may show pulmonary congestion, the European Respiratory Society notes that chest X-ray cannot definitively diagnose heart failure or quantify its severity 1.
- ECHO provides superior diagnostic information about ventricular function, valvular abnormalities, and hemodynamics that directly guide management 1.
Critical Clinical Pitfalls to Avoid
Do not delay cardiac evaluation by pursuing sleep studies first—the hypoxemia and orthopnea indicate potential acute decompensation requiring immediate assessment of cardiac function 1.
Do not dismiss nocturia as purely urological—it is a common symptom of heart failure due to nocturnal fluid redistribution and should prompt cardiac evaluation 1.
Recognize that clear lung fields do not exclude heart failure—early or predominantly right-sided heart failure can present with peripheral edema and hypoxemia before pulmonary crackles develop 1.
Complementary Initial Workup
While ECHO is the priority investigation, the European Society of Cardiology suggests simultaneously obtaining ECG and BNP as complementary cardiac markers 1, and the American College of Cardiology recommends checking basic metabolic panel, renal function, and HbA1c to identify contributing factors like chronic kidney disease or diabetes 1.