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.