Abstract
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Objectives Cardiac allograft vasculopathy (CAV) is the major determinant of long-term survival after orthotopic heart transplantation (OHT). We aim to evaluate the efficacy of quantitative cardiac PET with regadenoson as a noninvasive way to assess the early stages of CAV by measuring changes in myocardial blood flow (MBF).
Methods Nine patients (5 female; mean age 52 y) were enrolled 4.5 ± 2.5 y after OHT (Group 1), with no history of post OHT myocardial ischemia were enrolled in the study. Eleven subjects (Group 2) with intermediate pretest probability but not documented evidence for coronary artery disease were also included (9 female, mean age 70 y). Myocardial blood flow (MBF) was assessed using dynamic (13)N-ammonia PET (20 mCi intravenously) at rest and during regadenososn-induced hyperemia, and coronary flow reserve (CPR) was calculated as the ratio of hyperemic MBF to resting MBF. Regional qualitative (13)N-ammonia PET was assessed using a 5-point scoring system. Rest left ventricular ejection fraction was similar in both groups (49% for Group 1 and 53% for Group 2).
Results Regadenoson induced rate pressure product was similar within both groups (10998 and 10920 for Group1 and Group 2, respectively). No reversible regional myocardial perfusion defects were observe. Resting MBF was similar (1.14±0.29 and 1.01±0.24 mL/min/g for Groups 1 and 2, respectively, NS), while regadenoson-induced hyperemia produced a trend in MBF (2.27±0.56 and 2.59±0.49 mL/min/g for Groups 1 and 2, respectively, p<0.07). CFR demonstrated a diminished trend toward the group after OHT (2.10±0.68 and 2.62±0.74 for Group 1 and 2, respectively, P<0.06).
Conclusions This preliminary study suggests that changes in MBF assessed by non invasive quantitative regadenoson cardiac PET may confirm the early changes in CAV after OHT and seems to confirm that this is a progressive process, diffusely involving the epicardial and microvascular coronary system.