Noninvasive PET quantitative myocardial blood flow with regadenoson for assessing cardiac allograft vasculopathy in orthotopic heart transplantation patients

Abstract

Background Risk stratification and early detection of cardiac allograft vasculopathy (CAV) is essential in orthotopic heart transplantation (OHT) patients. This study assesses the changes in myocardial blood flow (MBF) noninvasively in OHT patients using quantitative cardiac PET with regadenoson. Methods Twelve patients (Group 1) (8 males, 4 females, mean age 55 ± 7 y) with no history of post OHT myocardial ischemia were enrolled after 5.4± 2.0 y after OHT. Fifteen patients (Group 2) (9 males, 6 females, mean age 71 ± 9 y) with intermediate pretest probability but not documented evidence for coronary artery disease (CAD) were also included to serve as control. Global and regional MBFs were assessed using dynamic 13N-NH3 PET at rest and during regadenoson-induced hyperemia. The coronary flow reserve (CFR) was also calculated as the ratio of hyperemic to resting MBF. Results Mean regadenoson-induced rate-pressure products were similar in both groups, while there was an increase in resting rate-pressure product in Group 1 patients. Both mean and median values of resting MBF were higher in Group 1 than Group 2 patients (1.33±0.31 and 1.01±0.21 mL/min/g for Groups 1 and 2, respectively, P<.001), while mean hyperemic MBF values were similar in both Groups (2.68±0.84 and 2.64±0.94 mL/min/g, P=NS) but median hyperemic MBF values were lower in Group 1 than Group 2 patients (2.0 vs. 2.60 mL/min/g, P=.018). Both mean and median CFR values demonstrated a significant reduction toward the Group 1 compared to Group 2 patients (2.07±0.74 vs. 2.63±0.48, P = .025). Conclusions This study suggests that the MBF in OHT patients may be abnormal at resting state with diminished CFR. This hints that the epicardial and microvascular coronary subsystem may be exacerbated after OHT leading to the gradual progression of CAV.

The role of non-invasive imaging modalities in cardiac allograft vasculopathy: an updated focus on current evidences

“…5 ). In a comparison study among PET, IVUS and ICA, 82 Rb-dipiridamole PET test demonstrated that the reduction in MBF and the concurrent increase in coronary resistance were highly suggestive of CAV, with > 96% specificity [ 77 ]. Moreover, myocardial flow reserve quantification using 13 NH 3 was inversely related to the volume of coronary plaques as estimated by IVUS, also when ICA was negative [ 78 ].…”

Quantitative myocardial perfusion response to adenosine and regadenoson in patients with suspected coronary artery disease

“…13 NH 3 is another excellent PET perfusion tracer with high extraction. Although there are a few cardiac PET studies in which regadenoson has been used together with 15 O-water 27 or 13 NH 3 PET, [28][29][30] there are no previous comparisons of the hyperemic effect of regadenoson versus adenosine or dipyridamole using an ideal PET perfusion tracer.…”

Quantitative Assessment of Myocardial Ischemia With Positron Emission Tomography

“…Stress MBF alone showed its role in detecting CAD 82,84 and was a potent outcome predictor of hypertrophic cardiomyopathy 85 . Elevated rest MBF was observed in patients with orthotopic heart transplantation, 86 and abnormal rest MBF was associated with major adverse cardiovascular outcomes such as unstable angina, non-ST and ST-elevation myocardial infarction, and stroke 87 …”

“…Stress MBF alone showed its role in detecting CAD 82,84 and was a potent outcome predictor of hypertrophic cardiomyopathy. 85 Elevated rest MBF was observed in patients with orthotopic heart transplantation, 86 and abnormal rest MBF was associated with major adverse cardiovascular outcomes such as unstable angina, non-ST and ST-elevation myocardial infarction, and stroke. 87 Also, because of the nature of tissue compartment models, absolute quantification like MBF in a physical unit of flow (/min) does not depend on accurate measurement of administrated activity because activity values are all cancelled out during kinetic modeling computation.…”