NITROGEN-13-AMMONIA AND PET TO DETECT ALLOGRAFT CORONARY-ARTERY DISEASE AFTER HEART-TRANSPLANTATION - COMPARISON WITH CORONARY ANGIOGRAPHY

The diffuse nature of allograft coronary artery disease (CAD) suggests that global myocardial blood flow (MBF) may decrease with time after transplantation; therefore the diagnosis of this disease remains probl ematic. Methods: To investigate whether PET detects a fall in allograf t MBF over time, PET scans (108) were obtained from 43 heart transplan t recipients. Thirty-five patients underwent two serial PET scans 1 yr apart. MBF was measured by PET using N-13-ammonia as a tracer. Corona ry angiography was performed parallel with PET imaging and compared wi th perfusion rates measured by PET scans. Results: MBF measured by PET decreased sequentially with time. The mean MBF was 73 +/- 21, 56 +/- 13, 51 +/- 11 and 51 +/- 27 ml/min/100 g of tissue in patients survivi ng 3 mo, 1, 2 and 3 yr after transplantation, respectively. Significan t MBF decrease occurred within 1 yr after transplantation. Sequential PET studies showed a decrease in MBF in 22 of 35 patients (63%). Mean MBF for the first and second scans was 65 +/- 18 and 54 +/- 16, respec tively. MBF decrease was more profound in patients (n = 11) angiograph ic evidence of CAD. There was a trend towards increased rejection and CMV infection rates in patients with decreased MBF. Conclusion: With t ime, PET detects a decrease in MBF in cardiac allografts. The frequenc y of MBF decrease detected by PET is concordant with the true incidenc e of allograft CAD, suggesting that sequential PET is a more sensitive modality for monitoring allograft CAD than angiography.