The role of non-invasive fractional flow reserve derived from coronary CT angiography in assessing the hemodynamic relevance of myocardial bridging

Abstract

Objective To evaluate the role of non-invasive fractional flow reserve (FFR) derived from coronary CT angiography (CCTA) in assessing the hemodynamic relevance of myocardial bridging (MB). Methods A total of 60 patients without obstructive coronary artery disease but with CCTA-confirmed MB of the left anterior descending coronary artery and 30 patients with negative CCTA findings as control group were retrospectively included in this study. The 60 patients with MB were divided into 2 groups (superficial and deep MB group) according to the depth of MB. Age and sex were matched among three groups. The location, length, depth, and degree of systolic compression of the MB were measured. The FFRCT values(including systolic and diastolic phases) were measured at three points (segments 1 to 2 cm proximal to a MB, mid-tunneled segment and segments 1 to 2 cm distal to the MB) by cFFR software. Patients with FFRCT<0.75 were deemed to have hemodynamic relevance (abnormal group). χ2 test, ANOVA test, Mann-Whitney U test, Kruskal-Wallis H test and logistic regression model were used for statistical analysis. Results The FFRCT values decreased from diastolic phase to systolic phase in deep MB group [0.90 (0.81-0.94) vs. 0.93 (0.91-0.97), Z=-2.172, P=0.03]. Compared to control group, the FFRCT values decreased in both diastolic phase and systolic phase in superficial MB group as well as deep MB group [systole 0.92 (0.90-0.94) control vs. 0.84 (0.77-0.88) superficial vs. 0.67 (0.50-0.88) deep, H=37.193, P<0.001; diastole 0.93 (0.89-0.94) control vs. 0.85 (0.73-0.92) superficial vs. 0.81 (0.65-0.87) deep, H=26.508, P<0.001]. Abnormal FFRCT values (<0.75) were found in 28 (47.7%) MB patients (9 superficial vs. 19 deep). The length (OR=1.067, 95% CI:1.016-1.122, P=0.010) and depth (OR=2.028, 95%CI:1.129-3.644, P=0.018) of MB were associated with the abnormal FFRCT values. Conclusions The FFRCT values of coronary artery distal to MB were lower than that without MB. Abnormal FFRCT values are more prevalent in deep MB. MB length and depth demonstrate moderate predictive value for an abnormal FFRCT value. Key words: Myocardial bridging; Tomography, X-ray computed; Fractional flow reserve