Most Appropriate Investigation: Echocardiogram (ECHO)
The most appropriate initial investigation is an echocardiogram (ECHO) to assess for heart failure, which is the most likely unifying diagnosis given the constellation of orthopnea, bilateral lower extremity edema, hypertension, and hypoxemia with clear lung fields. 1
Clinical Reasoning
This patient presents with a classic heart failure syndrome:
Orthopnea is a hallmark symptom of left ventricular dysfunction and elevated pulmonary capillary wedge pressure, indicating cardiac pathology rather than primary pulmonary disease 1
Hypoxemia (O2 sat 87%) with clear lung fields strongly suggests cardiac rather than primary pulmonary pathology, as pulmonary edema may be interstitial rather than alveolar in early heart failure 1
Bilateral lower extremity edema combined with orthopnea and hypertension points directly to volume overload from cardiac dysfunction 1
Why ECHO is the Priority
The American Heart Association recommends obtaining ECHO immediately to assess ventricular function, valvular disease, and pulmonary pressures in patients with suspected heart failure 1. This single test will:
- Definitively assess left and right ventricular systolic and diastolic function 1
- Identify valvular abnormalities contributing to symptoms 1
- Estimate pulmonary artery pressures 1
- Guide immediate therapeutic decisions regarding diuretics, afterload reduction, and need for advanced heart failure therapies 1
Why Not the Other Options
Sleep Study (Option A)
While daytime sleepiness and nocturia could suggest obstructive sleep apnea, 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 bilateral edema, orthopnea, and hypoxemia make heart failure the immediate concern that must be addressed first 1. OSA evaluation can follow once cardiac function is optimized 2.
Chest CT (Option C)
The European Respiratory Society states that CT has no role in the initial workup of suspected heart failure 1. CT would be indicated if there were concern for pulmonary embolism, interstitial lung disease, or malignancy—none of which fit this clinical picture 1.
Chest X-ray (Option D)
While CXR may show cardiomegaly or pulmonary vascular congestion, the European Respiratory Society notes that chest X-ray cannot definitively diagnose heart failure or quantify its severity 1. ECHO provides far superior diagnostic and prognostic information 1.
Critical Clinical Pitfalls
Do not delay cardiac evaluation by pursuing sleep studies first in patients with clear signs of volume overload 1. While OSA is common in patients with cardiovascular disease and can contribute to bilateral edema and pulmonary hypertension 3, 4, the immediate priority is assessing cardiac function 1
Nocturia in this context is likely due to nocturnal mobilization of peripheral edema rather than a primary urological or sleep disorder 2. Treating the heart failure will often improve nocturia 2
The combination of obesity, bilateral leg edema, and hypoxemia can represent either heart failure, OSA with pulmonary hypertension, or both 3, 4. However, orthopnea specifically points to elevated left-sided filling pressures requiring immediate cardiac assessment 1
Complementary Testing
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 1. These can be ordered alongside the ECHO but should not delay echocardiographic evaluation 1.