Abstract 15455: Unraveling the Mechanism of Ischemia in Pediatric Patients With R-AAOCA: Fixed and Dynamic Obstruction

Abstract

Introduction: Although rare, anomalous aortic origin of the right coronary artery (R-AAOCA) is associated with exercise-related sudden cardiac death and dynamic obstruction to coronary flow in the intramural segment has been proposed as the ischemia mechanism. We aim to describe fixed and dynamic obstruction mechanism of ischemia in select group of R-AAOCA patients undergoing invasive transcatheter stress FFR and iFR. Hypothesis: Ischemia in R-AAOCA involves a 2-tier mechanism involving both fixed and dynamic obstruction. Methods: Single institution retrospective study of R-AAOCA patients undergoing cardiac catheterization due to ischemic symptoms and negative perfusion defects on dobutamine stress CMRI. Coronary angiography was performed in all patients. Instantaneous wave-free ratio (iFR) and fractional flow reserve (FFR) were performed at baseline and under pharmacologic stress with adenosine (aFFR)/dobutamine (diFR) when the coronary ostium was engaged in a stable manner. Significant fixed obstruction was considered if aFFR<0.80 and dynamic if diFR <0.85. Results: A total of 14/446 (3%) R-AAOCA patients were included. In 10 patients, a Verrata pressure guide wire (Volcano, San Diego, CA) was able to be advanced to perform iFR and FFR. Fixed RCA obstruction was demonstrated in 4/10 patients (40%) and 2 of these (2/10, 20%) also had dynamic RCA obstruction (Table). All 4 patients were referred to surgery: 3 completed, 1 pending. In 4/14 (28%) patients, iFR and FFR were not performed due to inability to engage the RCA ostium, all of which found to be hypoplastic (1-1.5 mm) and slit-like at surgery. There were no procedural complications. Conclusions: In a small cohort of R-AAOCA patients, mechanisms for myocardial ischemia during stress suggest dynamic and fixed components. Our preliminary results provide important insight for risk stratification. Long-term follow-up will be important to validate the performance of iFR/FFR in R-AAOCA