Abstract
Introduction
Lateral wall 13N-ammonia perfusion defects may worsen during stress despite preserved stress myocardial blood flow (MBF) and myocardial flow reserve (MBFR). Their clinical significance after heart transplant (HT) is uncertain.Methods
Study retrospectively screened 266 HT recipients undergoing 13N-ammonia PET between 2021-2023 with normal or presumed normal variant lateral wall defects. PET findings were compared with coronary angiography and intravascular ultrasound. Phase-specific perfusion was assessed post hoc in patients with lateral wall defects.Results
Among 236 HT recipients, 80 (34%) demonstrated a lateral perfusion defect with preserved circumflex territory stress MBF and/or MBFR. Lateral perfusion defects were not associated with differences in demographics, comorbidities, hemodynamics, angiographic cardiac allograft vasculopathy, stress MBF, MBFR, or all-cause mortality. Most defects were partially reversible or reversible and localized to the basal lateral wall. These patients exhibited greater stress-induced LVEF augmentation, greater reduction of end-systolic volume with stress, and lower transient ischemic dilatation ratios. Among 79 patients with lateral wall defects undergoing phase-specific analysis, 73 (92.4%) defects resolved or improved at end-systole. Median summed stress score decreased from 3 [2-4] on phase-averaged images to 0 [0-1] at end-systole, and median summed difference score decreased from 2 [0.5-3] to 0 [0-0], while defects remained evident at end-diastole.Conclusion
Lateral wall defects with preserved circumflex flow were not associated with cardiac allograft vasculopathy or all-cause mortality. Their frequent improvement at end-systole suggests that cardiac motion and phase-dependent partial volume activity recovery may contribute, but this theory requires further validation.