Abstract Body (Do not enter title and authors here): Introduction/Background:
Positron emission tomography (PET) is a sensitive tool for the non-invasive assessment of cardiac allograft vasculopathy (CAV), a leading cause of long-term graft dysfunction in heart transplant patients. Early interventions to treat CAV are critical, however predicting which patients will go on to develop CAV is challenging. Whether PET myocardial perfusion imaging early after transplant can identify high risk patients is unknown. Towards this end, we sought to describe the prevalence of abnormal findings on baseline stress PET in early transplant patients.

Methods:
Patients < 4 years post-transplant who underwent stress PET myocardial perfusion imaging were retrospectively identified. The prevalence of abnormal quantitative and qualitative PET findings on their initial PET exam was determined. Abnormal stress flow was defined as <1.7 mL/min/g and abnormal flow reserve as <2.0. Patients were also classified by a validated PET CAV grading scheme.

Results:
We identified 213 patients with a mean age of 57.6 +/- 12.1 years and mean graft age of 2.3 +/- 0.8 years. Most patients had no prior angiographic CAV (90.6% CAV 0) with 8.5% having angiographic CAV 1, and 1% having angiographic CAV 2/3. The majority of patients were on tacrolimus (93%), mycophenolate (89%), aspirin (91%), and statin (93%). Within this population, there was a high prevalence of abnormal flow reserve (29.1%) with fewer patients having abnormal perfusion (12.7%) or abnormal stress myocardial blood flow (10.0%). A PET CAV grade 1 was identified in 17.4% of patients and a PET CAV grade 2/3 in 2.4%.

Conclusion:
A significant minority of patients early after transplantation who undergo stress PET myocardial perfusion imaging will have abnormalities on their initial baseline exam. Longitudinal studies are needed to determine whether abnormal non-invasive markers on PET can predict the onset of severe CAV and guide therapy.