Nonuniform flow dynamics in the aorta of normal children: A simplified approach to measurement using magnetic resonance velocity mapping

Purpose: To determine regional flow dynamics in the normal aorta (Ao) in children. Understanding flow dynamics in children is important in cardiovascular energetics, in designing improved aortic reconstructions by crafting the surgery to mimic normal aortic flow, and in Doppler flow calculations. The objective of this study was to determine regional flow dynamics in the normal Ao in children. Materials and Methods: We performed magnetic resonance velocity mapping on 13 subjects (ages 7.2 +/- 6.2 years) with normal Aos to determine flow dynamics in four equal quad-rants in the ascending (AAo) and descending aorta (DAo) aligned along the long axis of the Ao. Statistical significance was set at P <.05. Results: In the AAo, the left posterior quadrant displayed significantly less blood flow (16% +/- 5%) than the other quadrants (26-29%) over the cardiac cycle. In the DAo, both anterior quadrants carried significantly less blood flow (20% and 21%) than the posterior quadrants (27% and 32%). At maximum flow (15% +/- 5% into the cardiac cycle for the AAo: 27% +/- 15% for the DAo), there was significantly more flow in the right posterior quadrant (28% +/- 2%) than other quadrants (22-23%) in the AAo. In the DAo, both posterior quadrants had significantly higher flow rates (27% and 30%) than the anterior quadrants (21% and 22%). Maximum velocity in both the AAo and the DAo occurred in the left posterior quadrant in 10/13 at 16-24% into the cardiac cycle. At end-systole. a short flow reversal was noted in the posterior quadrants in the AAo In 11 / 13: in the DAo, this occurred in the anterior quadrants in 10/13. Conclusion: Flow dynamics in the normal Ao In children are not symmetrical: the flow distributions are asymmetric in both the AAo and the DAo throughout systole, including flow reversal related to the dicrotic notch. These results may help improve Ao surgery.