FRACTIONAL FLOW RESERVE (FFR) IN EVALUATION OF CORONARY ARTERY STENOSES: COMPARATIVE STUDY BETWEEN CORONARY COMPUTED TOMOGRAPHY ANGIOGRAPHY (CCTA) AND CONVENTIONAL CORONARY ANGIOGRAPHY (CCA)

Abstract

Coronary revascularization is often performed on an ad hoc basis from semi-quantitative measures of percent luminal diameter narrowing of the artery visualized at the time of invasive coronary angiography (ICA). This practice stems from the research of Gould et al., who elegantly demonstrated the relationship between stenosis and ischemia, as determined by myocardial blood flow reserve, wherein flow to the myocardium is compromised as the luminal diameter progressively narrows. This diminution in flow is most evident at hyperemic states and begins as early as 40% narrowing of vessel diameter, with more predictable reductions in hyperemic flow for stenoses > 70% (Taylor et al., 2013). However, the relationship between coronary stenosis and myocardial ischemia is more complex, with ensuing studies demonstrating an unreliable relationship between stenosis and ischemia. One example of this was highlighted in the nuclear substudy of the COURAGE (Clinical Outcomes Utilizing Revascularization and Aggressive Drug Evaluation) trial; in this study in patients with ≥ 70% stenosis, only 32% exhibited severe ischemia and 40% manifested no or mild ischemia according to myocardial perfusion scintigraphy (Shaw et al., 2008).