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Cardiac allograft vasculopathy (CAV) is a leading cause of morbidity after cardiac transplantation. Coronary angiography (ICA) with intravascular ultrasound (IVUS) is the gold standard test for CAV but has low sensitivity for early CAV. Fractional flow reserve (FFR) correlates with IVUS and is frequently abnormal in cardiac transplant recipients despite normal angiograms. We derived vessel quantitative flow ratio (QFR), an FFR-like parameter, retrospectively from ICA and hypothesized that QFR would predict subsequent CAV.
We reviewed 22 consecutive orthotropic heart transplantation recipients who underwent two separate routine coronary angiograms from January 2013 to April 2016. Coronary angiograms and IVUS were performed per local protocol at 1, 2, 3, and 5 years post-transplant. QFR was calculated using dedicated offline software (Medis, Leiden, the Netherlands), a validated algorithm not available for clinical use in the USA. CAV was assessed semi-quantitatively based on manual review of the ICA procedure report (0: none, 1: trivial, 2: non-obstructive CAV, 3: obstructive CAV). Median time from transplant to first included ICA was 2.1 years. QFR from the first ICA (QFR1) correlated well with the CAV score derived from the second ICA (CAV2) with a relative clustering of CAV at lower QFR1 values [Figure]. In an ROC analysis, an optimal QFR threshold of 0.88 yielded a sensitivity of 0.94 and a specificity of 0.67 (AUC 0.79) for at least non-obstructive subsequent CAV. We also found angiographically derived CAV severity poorly predicted subsequent CAV [Figure].
QFR is easily derived from invasive angiography and may predict subsequent early CAV in cardiac transplant patients. However, this finding is only exploratory, as QFR is not yet clinically available and needs to be assessed in a larger prospective cohort.