Abstract 15455: Increased Aortopulmonary Collateral Flow With Exercise is Associated With Improved Exercise Capacity.

Introduction: Aortopulmonary collateral (APC) flow is a common finding in the Fontan circulation. It has been suggested that these collaterals should be routinely embolised to reduce volume loading of the single ventricle. We aimed to assess the role of APC flow on the exercise capacity of patients with a Fontan circulation. Methods: As part of a Cross Sectional Study evaluating the Functional Outcomes of Fontan patients of Australia and New Zealand, patients with an extracardiac conduit or lateral tunnel Fontans were recruited. Patients with severe valve regurgitation or arch obstruction were excluded. Exercise capacity was measured by cardiopulmonary exercise testing. Each participant underwent a Cardiac MRI (Siemens 1.5T Aera) at rest and with supine exercise (Lode bicycle ergometer). Using standard MRI cine and flow assessment techniques ventricular volumes and flows were assessed. Cycling was briefly stopped (<30 seconds) for acquisition of data with breathhold during exercise stress. Collateral flow was derived from the difference between the ascending aortic and (total descending aorta and SVC flow). (AoA flow-(AoD+SVC flow). Results: Good quality data was obtained from 27 participants. Cardiac index increased from 3L/min/m2 on average at rest (+/-SD 0.81) to 4.4 L/min/m2(+/-SD 0.79; p=<0.001) at peak exercise and APC flow increased by 13% (+/-SD 47; p=0.06). APC during exercise flow corresponded to 13.3% of the ascending aortic flow on average (+/-SD 12.1). There was a nonsignificant positive correlation between APC flow at rest and % predicted VO2max (r=0.13; p=0.53). APC flow measured at peak exercise was associated with better exercise capacity (r=0.81, p=0.0016). There was no significant relationship between APC flow and ventricular volumes or cardiac index. Conclusion: Increased aortopulmonary collateral flow with exercise has a positive impact on the exercise capacity of patients with a Fontan circulation through augmentation of pulmonary blood flow and hence improved ventricular preload. [ABSTRACT FROM AUTHOR]