Abstract
The assessment of the left main coronary artery (LMCA) by coronary angiography has several limitations. The fractional flow reserve (FFR) is useful for the functional evaluation of LMCA stenoses. The instantaneous wave-free ratio (iFR), a resting index, was developed to simplify functional coronary assessment. However, its performance for LMCA stenoses has yet to be explored. The iFR was measured at rest, and the FFR was measured under maximal hyperemia. We calculated that a sample size of 90 lesions would have provided 90% power at a 5% significance level to detect an Area Under the Curve (AUC) < 0.7 for the iFR to identify FFR-positive stenoses. A total of 91 measurements were performed on angiographically intermediate LMCA stenoses at three centers. The comparison between the iFR and the FFR showed a significant correlation (r = 0.67, p < 0.001). At receiver operating characteristic (ROC) analysis, the iFR revealed a good diagnostic performance when compared to the FFR (AUC = 0.84; p < 0.001). A classification agreement between the iFR and the FFR was recorded in 81% of cases. The left ventricular ejection fraction (LVEF) was an independent predictor of the discrepancy between the FFR and iFR values (p = 0.040). The present study is the first demonstrating that the assessment of LMCA stenoses with the instantaneous wave-free ratio is a reliable adenosine-free alternative to classic fractional flow reserve. If confirmed in larger populations, these findings could be of relevance for real world daily practice.
Highlights
The quantitative evaluation of coronary angiography has limitations
Our results demonstrate that (1) the measurement of instantaneous wave-free ratio (iFR) is reliable in patients with left main coronary artery (LMCA) disease; (2) the iFR has good correlation and classification match with fractional flow reserve (FFR); (3) the diagnostic performance of the iFR is similar in stable coronary artery disease (CAD) or acute coronary syndrome (ACS) patients; (4) the adjustment of iFR results by the left ventricular ejection fraction (LVEF) improves its diagnostic performance to identify FFR-positive stenoses; (5) the presence of a
Our results demonstrate that (1) the measurement of iFR is reliable in patients with LMCA disease; (2) the iFR has good correlation and classification match with FFR; (3) the diagnostic performance of the iFR is similar in stable CAD or ACS patients; (4) the adjustment of iFR results by the LVEF improves its diagnostic performance to identify FFR-positive stenoses; (5) the presence of a further stenosis downstream of the target intermediate stenosis has an impact on both pressure indices
Summary
The quantitative evaluation of coronary angiography has limitations. More so with intermediate stenoses [1,2]. The short length, the frequent overlapping with side branches, the lack of a reference segment, the sometimes unavoidable “contrast streaming” at the ostium due to difficult catheter positioning, and the singular reverse tapering, such that its caliber often increases from the ostium to the distal section, make a precise angiographic evaluation of LMCA disease very difficult, even for experienced cardiologists [6]. The fractional flow reserve (FFR), calculated as the distal to proximal (aortic) pressure ratio during hyperemia, is currently the gold standard for the functional assessment of coronary stenoses’ severity, as its use has been associated with a clinical benefit in several studies [7,8,9]. The not infrequent presence of additional stenoses of downward vessels may have an impact on pressure measurements
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