Pulmonary and Aortic Blood Flow Measurements in Normal Subjects and Patients After Single Lung Transplantation at 0.5 T Using Velocity Encoded Cine MRI

Purpose: It is the purpose of this study to compare pulmonary and aortic blood flow measurements obtained in patients after single lung transplantation (SLTX) with those in volunteers. Methods/material: In nine patients after SLTX (three male, six female) and nine volunteers (seven male, two female), double oblique phase contrast cine-MRI sequences perpendicular to the direction of blood flow were obtained in the ascending aorta, main, right, and left pulmonary artery on a 0.5-T unit (Philips Gyroscan; Best, the Netherlands) (repetition time, 600 to 800 ms; echo time, 8 ms; alpha=30; field of view=280 mm matrix, 128×256, ECG gating, temporal resolution 16 time frames/RR interval). An initial in vitro study using the same sequence on a nonpulsatile flow phantom showed excellent correlation (r=0.99) between MRI measurements of flow velocity and flow volume and true velocity and flow volume. Measurements of blood flow volume (mL/min), peak mean systolic velocity, resistive index, and distensibility index were obtained in each vessel. Results: We found excellent correlations between left and right cardiac output as measured by velocity encoded cine-MRI (VEC-MRI) in the ascending aorta and main pulmonary artery both in normal volunteers (r=0.95) and in patients (r=0.91). Differential pulmonary blood flow measurements in volunteers showed that 55% of the right cardiac output was directed to the right and 45% to the left lung. Differential pulmonary blood flow in patients showed that most of the blood flow (81%) reaches the transplanted lung and only 19% reaches the patient's own lung (SLTX: 4.5±1.8 L/min, patient's own lung: 1.2±0.8 L/min). There were significant differences (p Conclusion: VEC-MRI blood flow measurements are a promising noninvasive tool to monitor the hemodynamic changes of pulmonary blood flow after SLTX. (CHEST 1998; 114:771–779) Abbreviations: AAO=ascending aorta; AF=antegrade flow; DI=distensibility index; EDV=End-diastolic velocity; LPA=left pulmonary artery; LTX=lung transplantation; MPA=main pulmonary artery; PSV=peak systolic velocity; PVR=pulmonary vascular resistance; RF=retrograde flow; RI=resistive index; RPA=right pulmonary artery; SLTX=single lung transplantation; VEC-MRI=velocity encoded cine-MRI