Evaluation of pulmonary artery flow in acute massive pulmonary thromboembolism with MRI

Objective: To probe into the value of MR imaging in evaluating the pulmonary artery hemodynamics and pulmonary artery pressure in acute massive pulmonary embolism. Methods: MR studies were performed in 21 patients with acute massive pulmonary embolism (diagnosed by contrast enhanced MR pulmonary angiography) and 20 healthy volunteers. The pulmonary artery hemodynamic parameters, such as the diameters of main and right pulmonary artery, peak velocity, average velocity, flow volume, flow patterns, and ejection acceleration time in main pulmonary artery were measured. The findings in patients and volunteers were compared. The hemodynamic parameters in patients were correlated with mean pulmonary artery pressure acquired with right heart catheterization. Results: The diameters of main pulmonary artery (2.93 vs 2.52 cm) and right pulmonary artery (2.49 vs 1.92 cm) in patients and volunteers showed significant differences (t=3.55, P<0.01 and t=4.19, P<0.01, respectively); Peak velocity (85.29 vs 100.63 cm/s), average velocity (11.00 vs 17.12 cm/s), flow volume (89.15 vs 98.96 ml/s), and ejection acceleration time (105.09 vs 163.85 ms) in main pulmonary artery were significantly different between patients and volunteers (t values were 2.89, 6.37, 2.21, and 9.46, respectively; P values were 0.01, <0.01, 0.03, and <0.01, respectively). The peak velocity-time curve of main pulmonary artery acquired with velocity encoded cine of MR in patients demonstrated earlier and lower peak velocity as well as abnormal retrograde flow. In addition, linear correlations were seen between the mean pulmonary pressure and the diameter of main pulmonary artery (r=0.62, P=0.001), diameter of right pulmonary artery (r=0.63, P=0.001), and ejection acceleration time (r=-0.55, P=0.005). Conclusion: MR imaging is a promising technique not only for the detection of pulmonary thromboemboli but also for the evaluation of hemodynamic parameters in pulmonary hypertension. (author)