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Four-dimensional aortic blood flow patterns in thoracic aortic grafts
H G Bogren1, M H Buonocore, D M Follette
1Department of Radiology, University of California-Davis, Medical Center, Sacramento, USA.
Insights
Magnetic resonance imaging reveals abnormal blood flow and significant energy loss in thoracic aortic grafts, particularly in atherosclerotic aneurysms. These findings highlight potential complications and areas for improved patient management.
Area of Science:
- Cardiovascular imaging
- Biomedical engineering
- Fluid dynamics
Background:
- Thoracic aortic grafts are crucial for managing aortic diseases.
- Understanding blood flow dynamics within these grafts is essential for assessing their function and potential complications.
Purpose of the Study:
- To investigate blood flow patterns in patients with thoracic aortic grafts using time-resolved, cardiac-gated, three-directional velocity data.
- To characterize flow abnormalities and associated energy losses in different types of aortic aneurysms and pseudoaneurysms.
Main Methods:
- Utilized magnetic resonance velocity-encoded phase contrast sequences to acquire detailed blood flow data.
- Analyzed flow patterns, including inflow/outflow jets and vortices, in 12 patients with various thoracic aortic pathologies.
Main Results:
- Observed flow abnormalities in all grafts, with more pronounced issues in atherosclerotic aneurysms compared to traumatic pseudoaneurysms.
- Identified persistent blood flow in vortices and prolonged transit times from the ascending to descending aorta.
- Quantified significant energy losses, potentially up to 33% of cardiac output in severe cases.
Conclusions:
- Thoracic aortic grafts can exhibit significant blood flow derangements and energy dissipation.
- Atherosclerotic aneurysms are associated with more severe flow abnormalities, including extensive vortex formation.
- These findings underscore the importance of advanced imaging techniques for evaluating graft performance and patient outcomes.
Abstract:
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.
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