Abstract 15103: Ventricular Work is Increased in the Presence of Ascending Aortic Aneurysms
External ventricular work is a measure of energy lost to the circulation and is directly proportional to ventricular afterload. Given that afterload is correlated to left ventricular dysfunction, and highly abnormal 3D flow patterns are observed in patients with ascending aorta (AAo) aneurysms, this study investigates the hypothesis that energy losses via viscous dissipation (VD) are increased in AAo aneurysm patients. As velocity distribution is a proxy measure for spatial velocity gradients, and thus energy loss through VD, the 3D blood velocity field was imaged using 4D flow sensitive MRI of the AAo in 24 subjects. This included 12 healthy control subjects and 12 patients with aortic aneurysms (Sinus of Valsalva or mid ascending aorta diameter >4 cm). Discrete velocity measurements were extracted from systolic streamlines emitted at the aortic root and the velocity distribution for each subject was calculated as the standard deviation of the velocity field. In addition, since abnormal flow patterns can create larger spatial velocity gradients and velocity distributions, subjects were examined for the presence of abnormal helical flow using a 4-point grading scale, tracking streamline rotation during one cardiac cycle (1: 0-180°, 2:180-360°, 3:360-720°, 4:>720°). Intergroup comparisons were analyzed using a Wilcoxon rank-sum test. Aneurysm patients exhibited helical grade 3-4 flow profiles throughout the ascending aorta; distinctly different from the cohesive, grade 1 patterns observed in controls (p>0.001). At the time of max flow, the average velocity distribution for aneurysm patients was 0.434 m/s ± 0.108 vs 0.227 m/s ± 0.063 for the healthy subjects (p>0.001). Therefore, we conclude that the velocity distribution, an indicator of energy loss, is greater in aneurysmal aortas than in healthy controls. Since adverse cardiovascular outcomes are associated with increased afterload, this may be a mechanism for heart failure in this patient population.
- © 2012 by American Heart Association, Inc.