American Board of Internal Medicine (ABIM) Certification Practice Exam

What is the preferred initial study to evaluate chronic thromboembolic pulmonary hypertension?

1. Chest X-ray

2. CT angiography

3. (V/Q) lung scan

4. Pulmonary function tests

The correct answer is: (V/Q) lung scan

The preferred initial study to evaluate chronic thromboembolic pulmonary hypertension (CTEPH) is a ventilation-perfusion (V/Q) lung scan. This imaging test is particularly valuable because it helps to identify areas of the lung that are receiving insufficient blood flow (perfusion), which is a hallmark of CTEPH. The V/Q scan compares ventilation, or how air is distributed in the lungs, to perfusion, or how blood flows through the lung's blood vessels. In cases of CTEPH, a V/Q scan typically shows mismatched results, where some areas are ventilated well but poorly perfused due to blocked or narrowed pulmonary arteries from chronic clotting. Recognizing these mismatches is crucial because they strongly suggest the presence of pulmonary emboli that have become organized, leading to the development of chronic hypertension in the pulmonary arterial system. By confirming perfusion defects where ventilation is normal, clinicians can direct further evaluation and management, possibly leading to the identification of candidates for surgical intervention, such as pulmonary endarterectomy. The result from a V/Q scan often influences the decision-making process for further diagnostic tests, including more invasive studies like pulmonary angiography, depending on its findings. While other options like chest X-ray, CT angi