Best investigation for pulmonary embolism ___:
**Core Concept**
Pulmonary embolism (PE) is a life-threatening condition caused by a blockage in one of the pulmonary arteries, typically resulting from a dislodged blood clot from the deep veins of the legs or pelvis. Accurate diagnosis of PE requires a combination of clinical assessment, imaging studies, and laboratory tests.
**Why the Correct Answer is Right**
The best investigation for pulmonary embolism is a computed tomography pulmonary angiography (CTPA), which provides high-resolution images of the pulmonary arteries and can detect clots as small as 1-2 mm. CTPA is non-invasive, widely available, and has a high sensitivity and specificity for diagnosing PE. It also allows for the assessment of other pulmonary abnormalities, such as infarction or chronic thromboembolic disease.
**Why Each Wrong Option is Incorrect**
**Option A:** Chest X-ray is not sensitive or specific for diagnosing PE and may show nonspecific signs such as atelectasis or pleural effusion.
**Option B:** Ventilation-perfusion scan (V/Q scan) is less sensitive than CTPA and may require additional testing to confirm or rule out PE.
**Option C:** Pulmonary angiography is an invasive procedure that carries a higher risk of complications than CTPA and is typically reserved for situations where CTPA is inconclusive or not available.
**Clinical Pearl / High-Yield Fact**
When interpreting CTPA images, it's essential to look for the "Westermark sign," a characteristic pattern of oligemia (reduced blood flow) in the lung periphery, which is highly suggestive of PE.
**Correct Answer: CTPA (Computed Tomography Pulmonary Angiography)**