Magnetic resonance imaging provides evidence for remodeling of the right ventricle after single-lung transplantation for pulmonary hypertension

Background: In end stage pulmonary hypertension (PH), the degree of right ventricular (RV) dysfunction has been considered so severe as to require combined heart-lung transplantation. Nevertheless, left ventricular (LV) and RV hemodynamics return to relatively normal levels after single- lung transplantation (SLT) alone. Accordingly, to test the hypothesis that LV and RV systolic function improves after SLT and that the dilated, thick walled RV reverts to more normal geometry, we used cine MRI and finite- element (FE) analysis to study patients with end-stage PH. Methods and Results: Seven patients with end stage PH underwent cine MRI before and after SLT, and eight normal volunteers were also imaged with cine MRI. Short-axis images at the midventricular level were analyzed with customized image- processing software. The LV and RV ejection fractions, velocity of fiber shortening, RV end-diastolic (ED) and end-systolic (ES) chamber areas, and RV ES and ED wall thicknesses were calculated directly from the MRI images. Two dimensional FE models of the heart were constructed from the MRI villages at early diastole. LV and RV pressures were measured in the patients with a cardiac catheterization before and after SLT. Models were solved to yield diastolic LV, RV, and septal wall stresses. By use of a nonlinear optimization algorithm, LV and RV diastolic material properties were determined by minimization of the least-squares difference between FE model- predicted and MRI-measured LV, RV, and epicardial chamber areas and circumferences. The results demonstrated a substantial reduction in RV wall stress after SLT (1.8x10⁵ dynes/cm² pre-SLT to 2x10⁴ dynes/cm² post SLT; P<.001). The average RV diastolic elastic modulus was reduced significantly after SLT (1.5 x 10⁶ dynes/cm² pre-SLT to 1 x 10⁵ dynes/cm² post-SLT; P=.01), but there was no change in the LV elastic modulus. RV velocity of fractional shortening increased significantly after SLT (0.23 pre-SLT to 0.58 post-SLT, P=.02), and RV ED and ES wall thicknesses were reduced significantly (ED, 0.86 cm pre SLT to 0.65 cm post-SLT, P=.03 and ES, 1.06 cm pre-SLT to 0.72 cm post-SLT, P=.005). Conclusions: These results provide evidence supporting the contention that LV and RV systolic function improved after SLT for end-stage PH and that the RV underwent significant remodeling within 3 to 6 months after lung transplantation.