Temporal changes in CT-derived fractional flow reserve in patients after heart transplantation

Background: Adding functional information by CT-derived fractional flow reserve (FFRct) to coronary CT angiography (CCTA) and assessing its temporal change may provide insight into the natural history and physiopathology of cardiac allograft vasculopathy (CAV) in heart transplantation (HTx) patients. We assessed FFRct changes as well as CAV progression over a 2-year period in HTx patients undergoing serial CT imaging. Methods: HTx patients from Erasmus MC and Mount Sinai Hospital, who had consecutive CCTAs 2 years apart were evaluated. FFRct analysis was performed for both scans. FFRct values at the most distal point in the left anterior descending (LAD), left circumflex (LCX), and right coronary artery (RCA) were measured after precisely matching the anatomical locations in both analyses. Also, the number of anatomical coronary stenoses of > 30% was scored. Results: In total, 106 patients (median age 57 [interquartile range 47–67] years, 67% male) at 9 [6–13] years after HTx at the time of the baseline CCTA were included. Median distal FFRct values significantly decreased from baseline to follow-up for the LAD from 0.85 [0.79–0.90] to 0.84 [0.76–0.90] (p = 0.001), LCX from 0.92 [0.88–0.96] to 0.91 [0.85–0.95] (p = 0.009), and RCA from 0.92 [0.86–0.95] to 0.90 [0.86–0.94] (p = 0.004). The number of focal anatomical stenoses of > 30% increased from a median of 1 [0–2] at baseline to 2 [0–3] at follow-up (p = 0.009). Conclusions: The distal coronary FFRct values in post-HTX patients in each of the three major coronary arteries decreased, and the number of focal coronary stenoses increased over a 2-year period. Temporal FFRct change rate may become an additional parameter in the follow-up of HTx patients, but more research is needed to elucidate its role. Clinical relevance statement: CT-derived fractional flow reserve (FFRct) is important post-heart transplant because of additional information on coronary CT angiography for cardiac allograft vasculopathy (CAV) detection. The decrease and degree of reduction in distal FFRct value may indicate progression in anatomic CAV burden. Key Points: CT-derived fractional flow reserve (FFRct) is important for monitoring cardiac allograft vasculopathy (CAV) in heart transplant patients. Over time, transplant patients showed a decrease in distal FFRct and an increase in coronary stenoses. Temporal changes in FFRct could be crucial for transplant follow-up, aiding in CAV detection.