FFRCT and stress perfusion CMR are equally reliable alternatives To invasive FFR measurement in functional significance of intermediate-grade coronary artery stenosis

Purpose: The management of intermediate-grade coronary artery stenoses (CAS) is challenging, often requiring additional invasive work-up with fractional flow reserve (FFR) to guide revascularization. To correlate the FFR estimates derived from computed tomography (FFRCT) and stress perfusion cardiac magnetic resonance (CMR) with invasive FFR, the standard in predicting functional significance of intermediate-grade CAS (i.e.40-70% diameter narrowing).
Methods & Materials: Thirty-seven patients (mean age 61±9 years;25 males) who underwent coronary CT angiography, adenosine first-pass CMR, quantitative coronary angiography and FFR in the work-up for intermediate-grade CAS (n=39) were retrospectively evaluated. Blinded FFRCT analysis was computed on each intermediate-grade CAS. Adenosine myocardial perfusion indices (MPI) parameters were evaluated on semi-quantitative CMR in both the subendocardial myocardium supplied by the CAS and in remote (presumed normal) myocardium. Stress subendocardial MPI in RISK segments (RISK) and the correction by including remote subendocardial MPI (RISKcorr) were analyzed and correlated to the FFR and FFRCT values. Differences in correlations with FFR between CMR parameters and FFRCT were tested with z statistics and considered statistically significant different at 0.05 level.
Results: The average FFR value was 0.85±0.10(0.60-0.99 range), 28% lesions (n=11) were ≤0.80. FFR value correlated poorly with the RISK MPI (r=0.151;p=0.36), but equally strongly with FFRCT (r=0.675;p<0.001) and the RISKcorr MPI (p-value RISKcorr model versus FFRCT=0.01).
Conclusion: Assessment of the functional significance of intermediate-grade CAS estimated from FFRCT and stress perfusion CMR correlates strongly with invasive FFR. Both techniques may be used as equally reliable alternatives to guide patient selection for revascularization.