Exercise Phase-Contrast Magnetic Resonance Angiography to Assess Hemodynamics and Cardiopulmonary Adaptations: A Pilot Study

Objectives: Assessment of aortic and pulmonary artery flow parameters are routinely performed by phase-contrast magnetic resonance angiography (PCMRA) at rest in patient with congenital heart disease. However, little data exist on hemodynamic adaptations in this patient group during physiological exercise. This could facilitate understanding of pathophysiological mechanisms of exercise limitations.

Methods: Nine healthy adult volunteers (mean age: 37.4 years) underwent PCMRA at rest and during HR-targeted submaximal aerobic lower limb supine exercise. An MRI compatible cycle ergometer (Lode BV Groningen) was used mounted onto a whole body MRI system (Siemens Avanto 1.5T, Siemens Medical Solutions, Erlangen). Pulse-gated free breathing PCMRA was performed in aorta (Ao) and pulmonary artery (PA) at TE 2.2 ms, TR 29.9 ms, slice thickness 5 mm, FOV to match anatomy, 2 averages, 30 reconstructed phases.

Results: Exercise intensity related increase in HR (rest: 69 ± 10.3 bpm, exercise: 120 ± 13.9 bpm) resulted in cardiac output increase (6.5 ± 1.4 L/min to 12.4 ± 1.8 L/min), Ao systolic peak velocity increase from 88.8 ± 14 cm/s to 121.9 ± 34.2 cm/s (p= 0.016), PA systolic peak velocity from 85.7 ± 17.8 cm/s to 140.2 ± 48.1 cm/s (p= 0.007), PA systolic peak flow rate from 409.7 ± 80.2 mL/s to 576.8 ± 180 mL/s (p= 0.006), Ao systolic peak flow rate from 414.6 ± 83 mL/s to 550.1 ± 135.1 mL/s (p= 0.002).

Conclusion: PCMRA can reliably quantify stroke volume, cardiac output, and aortic and pulmonary flow adaptations to exercise. In healthy volunteers, aerobic exercise leads to a significant increase in systolic peak velocity and peak instantaneous flow rate. Our methodology can help advance knowledge on cardiopulmonary regulations during exercise in patients with congenital heart disease.