Energy efficiency and pulmonary artery flow after balloon pulmonary angioplasty for inoperable, chronic thromboembolic pulmonary hypertension: Analysis by phase-contrast MRI

Abstract

Purpose: The aims of this study were to propose a new quantitative method for pulmonary artery (PA) flow energetics using phase-contrast magnetic resonance imaging (PC-MRI), and to investigate how balloon pulmonary angioplasty (BPA) impacts energetics in chronic thromboembolic pulmonary hypertension (CTEPH).

Materials and methods: PC-MRI at 3-Teslar and with a flow sensitive gradient echo was used to examine energetics prior to and following BPA for 24 CTEPH patients. Stroke volume (m; ml) and mean velocity (V; mm/s) for the main pulmonary artery (PA), right PA, and left PA were calculated from a time-flow curve derived from PC-MRI. Based on the Bernoulli principle, PA energy was identified as 1/2mV² (μj/kg), and energy loss was defined as the following equation "energy loss=main PA energy-(rt. PA energy+lt. PA energy)".

Results: Right PA energy was significantly greater post-BPA than pre-BPA (61±55 vs. 32±40μj/kg). There was no difference in main PA and left PA energies. Energy loss was significantly decreased post-BPA (18±97μj/kg) than pre-BPA (79±125μj/kg). An optimal cutoff of left PA energy of 45μj/kg pre-BPA can be used to predict patients with mPAP≥30mmHg after BPA, with an area under the curve of 0.91, 78% sensitivity, and 92% specificity.

Conclusion: Analysis of PA energetics using phase-contrast MRI demonstrates that BPA improves energy loss in CTEPH. In addition, BPA responses can be predicted by PA energy status pre-treatment.

Keywords: Balloon pulmonary angioplasty; Chronic thromboembolic pulmonary hypertension; Energy efficiency; Phase-contrast MRI.