The need for adenosine administration to achieve maximal hyperaemia limits the widespread application of fractional flow reserve (FFR) in the real world. We previously demonstrated that Pd/Pa ratio registered during submaximal reactive hyperaemia induced by conventional non-ionic radiographic contrast medium (contrast medium induced Pd/Pa ratio: CMR) can be sufficient for the assessment of physiological severity of stenosis in the majority of cases. In this study we aimed to test the accuracy of CMR in predicting an FFR≤0.80 in comparison with other adenosine-free indexes, such as basal Pd/Pa and instantaneous wave-free ratio (iFR).Methods
450 patients with 532 intermediate coronary stenoses were prospectively and consecutively enrolled. FFR was measured after administration of adenosine, CMR was obtained after intracoronary injection of 6 ml of radiographic contrast medium, while Pd/Pa and iFR were measured at rest.
Pd/Pa was measured in all 532 lesions, while CMR in 405 and iFR in 95. Although we found a significant correlation between FFR and all measured indexes, the strongest correlation was between FFR and CMR (r=0.89, p<0.001; r=0.73, p<0.001 for correlation between FFR and Pd/Pa; r=0.67, p<0.001 for correlation between FFR and iFR). ROC curve analysis confirmed these data, showing an excellent accuracy of CMR cut-off of ≤0.83 in predicting a positive FFR (AUC 0.97 [95% CI: 0.95-0.99], specificity 0.99, sensitivity 0.82). Moreover CMR was superior than basal Pd/Pa≤0.92 (AUC 0.89 [95% CI: 0.86-0.92], specificity 0.84, sensitivity 0.80; p<0.001) and iFR ≤0.88 (AUC 0.92 [95% CI: 0.85-0.97], specificity 0.94, sensitivity 0.75; p=0.018) in predicting a positive FFR, and the two resting methods were not different (p=0.674).
in the present study we confirm in a much larger population our previously published data, showing that CMR is accurate in predicting the functional significance of coronary stenosis but also we demonstrate its superiority over other adenosine-free indexes (Pd/Pa and iFR), which moreover have the same power in predicting FFR. This finding support the use of CMR in clinical practice, limiting the use of adenosine to doubtful cases.