4D-flow MRI assessment of blood flow before and after endovascular intervention in a patient with pulmonary hypertension due to isolated pulmonary artery involvement in large vessel vasculitis

A 43-year-old woman presented with dyspnea during exertion and lower leg edema. Contrast-enhanced computed tomography images demonstrated extensive proximal narrowing in the right main pulmonary artery with thickening and enhancement. Right heart catheterization revealed the presence of precapillary pulmonary hypertension with a mean pulmonary arterial pressure of 45 mm Hg. The patient was diagnosed with large-vessel vasculitis with isolated pulmonary artery involvement. Takayasu's arteritis was suspected, but histological examination was not performed. Several sessions of pulmonary arterial intervention were stratified for the right main pulmonary artery. After treatment, mean pulmonary arterial pressure had decreased to 22 mm Hg with improvement in symptoms. Thoracic 4D-flow magnetic resonance imaging was performed before and after intervention to evaluate the volume flow rates of pulmonary arteries. The rates increased at the inlet of the right pulmonary artery (before: 23 mL/s vs after: 47.5 mL/s) and the main pulmonary artery (before: 71.2 mL/s vs after: 82.5 mL/s), and decreased at the inlet of the left pulmonary artery (before: 46.2 mL/s vs after: 31.7 mL/s). The split ratio of volume flow rate between the right and left pulmonary arteries improved after treatment (before. right:left = 33.1:66.9; after, right:left = 60.0:40.0), approaching normal values. This report quantitatively describes perioperative hemodynamic changes in a patient with pulmonary hypertension using 4D-flow magnetic resonance imaging. Stent placement for stenosis in the right pulmonary artery resulted in an increase in overall pulmonary blood flow and also improved blood flow balance between the right and the left pulmonary arteries.