Virtual Fractional Flow Reserve in Heart Transplant Recipients with and without Graft Vasculopathy

Abstract

Cardiac graft vasculopathy (CAV) remains the Achilles' heel of long-term survival after heart transplantation (HTx). The severity and extent of CAV is graded with conventional coronary angiography(COR) which has several limitations. Recently virtual fractional flow reserve (vFFR) derived from COR has emerged as a new diagnostic computational tool to functionally evaluate the extent of coronary artery disease. The present study assessed the usefulness of vFFR to detect CAV in HTx recipients. In HTx pts referred for annual check-up, undergoing surveillance COR and normal LV systolic function, the extent of CAV was graded according to the ISHLT guidelines. Three-dimensional coronary geometries were constructed offline and generic boundary conditions for computational fluid dynamics analysis were applied to calculate vFFR. In 49 HTx pts with a mean age of 53.3 ± 11.0 years, 8.6 ± 7.1 years post HTx, a total number of 171 vessels(59 LAD, 60 Cx, 52 RCA) were analyzed. Mean vFFR in all HTx pts was 0.85 ± 0.15, median 0.89 [IQR 0.80, 0.95]. HTx pts with previous history of ischemic cardiomyopathy(ICMP) had significantly lower vFFR as compared to those with non-ICMP. Use of vFFR reclassified 33% of patients compared to the anatomical ISHLT criteria. A vFFR ≤ 0.80 was present in 24 pts (42 vessels). Despite a CAV score of 0, a pathological vFFR ≤ 0.80 was detected in 6 pts (25.0 %). Finally, pts with a vFFR ≤ 0.80 had significantly higher need for revascularization (Figure 1) vs those with normal vFFR (HR 9.18, 95% CI 1.18 to 71.2, p=0.03). The impairment of coronary flow assessed by vFFR in a subgroup of pts without CAV according to standard ISHLT criteria, suggests the presence of a diffuse vasculopathy undetectable by conventional COR. Similar to coronary atherosclerosis, a pathological vFFR bears prognostic information as evidenced by a higher need for revascularization when vFFR is low. Therefore, we speculate that vFFR may be a helpfull tool in risk stratification post HTx.