Postprandial Changes in Thoracic Aortic Flow Detected by 4D Flow MRI May Influence Study Results

While there is a growing body of data using 4D flow MRI to distinguish between normal and abnormal blood flow values in the thoracic aorta, the extent of physiological variation or lack thereof is potentially undervalued. Physiological processes such as postprandial changes to hemodynamics might influence data, normal values, follow-up studies, and data compared between study sites.

To determine the influence of food intake on flow parameters in the thoracic aorta of young healthy volunteers by 4D flow MRI.

Prospective.

20 young healthy (10 male, 10 female) volunteers were recruited for this study.

3T/4D flow MRI (three-dimensional time-resolved phase-contrast spoiled gradient-echo with three-directional velocity-encoding). Technical parameters were chosen according to consensus recommendations, including the use of a respiratory navigator, included a 10 mm respiratory navigator window, retrospective ECG gating, VENC 180-200 cm/s, voxel size 2.5 × 2.5 × 2.0-2.5 mm³, temporal resolution 41 ms and parallel imaging with acceleration factor of 4. Acquisition time was 10.3 ± 2.4 min.

Volunteers' thoracic aorta was imaged after fasting (food ≥ 6 h, liquid ≥ 2 h) and after a meal challenge to detect changes in aortic hemodynamics (stroke volume, flow, and velocity).

Statistics included calculation of relative difference (RD), two-tailed paired t-test, and Pearson coefficient. p < 0.05 was considered significant.

4D flow MRI detected statistically significant postprandial increases in stroke volume (pre: 93 ± 18 mL; post: 99 ± 24 mL, RD = 5 ± 13%), peak flow (pre: 433 ± 95 mL/s; post: 467 ± 95 mL/s, RD = 9 ± 14%), peak average velocity (pre: 73 ± 18 cm/s; post: 78 ± 16 cm/s, RD = 8 ± 11%), and maximum velocity (pre: 118 ± 24 cm/s; post: 131 ± 23 cm/s, RD = 11 ± 11%); values given for ascending aorta. 74% of individuals presented with postprandial increase in peak flow and velocities throughout the thoracic aorta.

Food intake triggers a small but significant increase in stroke volume, flow, and velocity in the aorta in young healthy individuals. Depending on the study question and potential longitudinal comparisons, one may consider introducing a fasting period prior to 4D flow MRI to avoid measurements at peak postprandial hyperemia.

2.

Stage 3, diagnostic thinking.