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 images 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 maternal properties were determined by minimization of the leastsquares 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 (1.8 x 10(5) dynes/cm2 pre-SLT to 2 x 10(4) dynes/cm2 post-SLT; P < .001). The average RV diastolic elastic modulus was reduced significantly after SLT (1.5 x 10(6) dynes/cm2 pre-SLT to 1 x 10(5) 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.