The FFR grey zone* refers to intermediate coronary lesions being arterial narrowing of moderate severity—typically 40–70% stenosis with FFR values ranging from 0.7 to 0.85, indicating a region of clinical uncertainty concerning the actual level of ischemia in patients with stable coronary artery disease (CAD).

Coronary artery disease (CAD) is a widespread heart condition marked by the accumulation of atherosclerotic plaque within the artery lumen. This buildup restricts blood flow, leading to decreased oxygen delivery to the myocardium. CAD stands as the leading cause of significant morbidity and mortality both in the United States and globally.

What are the 4 stages of CAD?

The staging system describes patients based on either the total plaque volume or percent atheroma volume, which is the proportion of arterial walls occupied by plaque. Stages are defined as normal (no plaque), mild, moderate, and severe plaque.