American Board of Internal Medicine (ABIM) Certification Practice Exam

What is the preferred stress test for patients with LBBB or a paced rhythm?

1. Traditional exercise stress test

2. Vasodilator study using adenosine or dipyridamole

3. Nuclear stress test with dobutamine

4. Holter monitoring during exercise

The correct answer is: Vasodilator study using adenosine or dipyridamole

In patients with left bundle branch block (LBBB) or a paced rhythm, the preferred stress test is a vasodilator study using agents such as adenosine or dipyridamole. This preference stems primarily from the fact that traditional exercise stress testing can produce inaccurate results in these patients due to the altered conduction pathways. LBBB and pacing can obscure the electrocardiographic (ECG) changes typically associated with myocardial ischemia, leading to potentially misleading findings. The vasodilator agents work by inducing a hyperemic response in the coronary circulation, allowing for the assessment of perfusion abnormalities without relying on the heart's electrical conduction system. This is particularly advantageous in patients where exercise-induced stress may not elicit clear ischemic changes. While a nuclear stress test with dobutamine can also be a valid alternative, it is more commonly reserved for patients who are unable to undergo exercise testing due to various physical limitations rather than specific conduction abnormalities. In contrast, traditional exercise stress tests are not ideal in this scenario due to the potential for misinterpretation of results linked to the changes in the ECG trace. Vasodilator studies therefore provide a safer, more reliable method for evaluating the cardiac health of patients with LBBB or paced rhythms, ensuring