High-resolution phase-contrast MRI of aortic and pulmonary blood flow during rest and physical exercise using a MRI compatible bicycle ergometer

Purpose: To establish high-resolution phase-contrast magnetic resonance imaging (PC-MRI) using a MRI compatible bicycle ergometer to quantify aortic and pulmonary blood flow during resting conditions and exercise.

Materials and methods: In 20 healthy volunteers (mean age, 26.8±5.0 years) high-resolution PC-MRI (mean temporal resolution, 7.4±3.2 ms) was performed in the ascending aorta (AA) and main pulmonary artery (PA) during physical rest and three exercise stages: stage 1, no-load operation; stage 2, heart rate increase 40% compared to rest; stage 3, heart rate increase 80% compared to rest. Flow quantification in AA and PA included flow volume (FV), average velocity (AV), peak velocity (PV) and time to PV (TP).

Results: In stage 1 only TP demonstrated a significant change. With progression to stage 2, all parameters altered significantly. Flow measurements during stage 3 evidenced further alterations only of AV and TP regarding both AA and PA. The deviation of the heart rate from the desired target value was significantly higher for stage 3 compared to stage 2, and 15% of the subjects did not reach the desired target heart rate of stage 3 at all.

Conclusion: Flow quantification by high-resolution PC-MRI during exercise using a MRI compatible bicycle ergometer is feasible. Medium exercise stages are necessary and sufficient to demonstrate flow alterations in healthy volunteers. PC-MRI ergometry may give insights into aberrant hemodynamic conditions in patients with cardiovascular and pulmonary disease.