Four-dimensional aortic blood flow patterns in thoracic aortic grafts

Time-resolved cardiac gated three-directional velocity data obtained with magnetic resonance velocity-encoded phase contrast sequences were used to study blood flow patterns in thoracic aortic grafts. Twelve patients were studied 6 with traumatic descending aortic pseudoaneurysms, 3 with atherosclerotic aneurysms, and 3 with dissecting aneurysms. All grafts had an inflow jet; outflow jet; and/or vortices proximal, in, or distal to the graft. Flow abnormalities were generally mild in the descending aortic traumatic pseudoaneurysms seen in young people. The atherosclerotic aneurysms seen in elderly patients had the most abnormal flows with multiple vortices in and outside the graft. Blood persisted up to one and a half heartbeats in some vortices and took three to five heartbeats to flow from ascending to descending aorta compared with two to three in age-matched normal subjects. Rather large energy losses, probably up to 33% of the cardiac output in our worst case, may occur in thoracic aortic grafts.