American Board of Internal Medicine (ABIM) Certification Practice Exam

What percentage obstruction is indicative of obstructive coronary artery disease (CAD)?

1. 50%

2. 70%

3. 90%

4. 100%

The correct answer is: 70%

Obstructive coronary artery disease (CAD) is typically characterized by a significant reduction in the diameter of the coronary arteries, leading to restricted blood flow during periods of increased myocardial demand, such as exercise or stress. While various factors can contribute to the clinical significance of coronary artery blockages, a general consensus in cardiology suggests that a 70% stenosis is often used as a threshold for determining obstructive CAD. At 70% obstruction, not only is there a considerable reduction in blood flow at peak myocardial oxygen demand, but this level of narrowing is also associated with a higher risk of ischemic symptoms, such as angina, and the potential for adverse cardiovascular events. Consequently, identifying a blockage of this magnitude is crucial for clinical decisions regarding the need for interventions like angioplasty or coronary artery bypass grafting. Although higher degrees of obstruction (like 90% or 100%) indicate even more severe disease and may lead to critical ischemia at rest, the defining point for obstructive CAD in adults is most commonly represented by the 70% threshold. It's important to note that 50% stenosis, while indicative of potential coronary artery disease, generally does not qualify as "obstructive" in the same way as 70