Author + information
- Alberto Ranieri De Caterina, MD∗ (, )
- Antonio Maria Leone, MD, PhD and
- Filippo Crea, MD, PhD
- ↵∗Department of Cardiology, Catholic University of the Sacred Heart, Largo Agostino Gemelli, 1, Rome, Italy 06100
We read with interest the paper on the FIRST (Fractional Flow Reserve and Intravascular Ultrasound Relationship) study, which compared the diagnostic accuracy of intravascular ultrasound (IVUS) with fractional flow reserve (FFR) in a vast population of 367 intermediate coronary lesions, angiographically defined as 40% to 80% luminal narrowing (1). In their conclusions, the authors mainly attributed the weak correlation between IVUS and FFR to the dependence of FFR on vessel size and propose different minimal lumen area (MLA) cutoffs on the basis of reference vessel diameter. We believe there is more to say.
The key concept that drives FFR-based evaluation is that it takes into account not just the severity of the lesion, but also the amount of myocardium subtended to it. In a similar population of 213 lesions, we have recently demonstrated that the myocardium at risk, assessed with the angiographic Jeopardy score, as well as the presence of collateralized chronic total occlusion in another vessel, were independent predictors of FFR ≤0.80 (2). Of note, the Jeopardy score showed closer correlations with FFR compared with 2-dimensional quantitative coronary angiography, such as MLA or cross-sectional stenosis. Conversely, vessel diameter provides only an indirect estimation of the amount of ischemic myocardium subtended to a stenosis and, for example, does not consider whether or not the myocardium is viable. In the present study, patients with previous myocardial infarction accounted for almost one-third of the total population.
The primary role of myocardium at risk explains certain unwritten rules of FFR. First, as also observed by the authors, the location of the lesion on the left anterior descendent (LAD) coronary artery, which generally perfuses a larger amount of myocardium compared with the left circumflex (LCX) and right coronary artery, is an independent predictor of positive FFR at multivariate analysis. Second, although the use of anatomical cutoffs considers a coronary vessel as a pipe in which a fixed stenosis reduces distal pressure and flow, FFR takes into account the complexity of coronary circulation distal to the stenosis, being influenced by the fundamental contribution of coronary collaterals, whose presence often is crucial to determine whether or not myocardium is subjected to ischemia. Finally, the importance of the amount of myocardium at risk explains why FFR is not just a diagnostic, but also a prognostic tool.
For all these reasons, as opposed to the authors, we do not hope that a FAME (Fractional Flow Reserve Versus Angiography for Multivessel Evaluation)-like trial comparing IVUS versus angiographic guidance would ever be designed. For intermediate coronary stenoses, we strongly suggest that functional rather than anatomical assessment should always guide revascularization, and we believe that the results of the FIRST study are in line with this message.
- American College of Cardiology Foundation
- Waksman R.,
- Legutko J.,
- Singh J.,
- et al.
- Leone A.M.,
- De Caterina A.R.,
- Basile E.,
- et al.