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 rig ht ventricular (RV) dysfunction has been considered so severe as to re quire combined heart-lung transplantation. Nevertheless, left ventricu lar (LV) and RV hemodynamics return to relatively normal levels after single-lung transplantation (SLT) alone. Accordingly, to test the hypo thesis that LV and RV systolic function improves after SLT and that th e dilated, thick-walled RV reverts to more normal geometry, we used ci ne MRI and finite-element (FE) analysis to study patients with end-sta ge PH. Methods and Results Seven patients with end-stage PH underwent cine MRT before and after SLT, and eight normal volunteers were also i maged with cine MRI. Short-axis images at the midventricular level wer e analyzed with customized image-processing software. The LV and RV ej ection 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 mode ls of the heart were constructed from the MRI images at early diastole . LV and RV pressures were measured in the patients with a cardiac cat heterization before and after SLT. Models were solved to yield diastol ic LV, RV, and septal wall stresses. By use of a nonlinear optimizatio n algorithm, LV and RV diastolic material properties were determined b y minimization of the least-squares difference between FE model-predic ted and MRI-measured LV, RV, and epicardial chamber areas and circumfe rences. The results demonstrated a substantial reduction in RV wall st ress after SLT (1.8 X 10(5) dynes/cm(2) pre-SLT to 2 X 10(4) dynes/cm( 2) post-SLT; P<.001). The average RV diastolic elastic modulus was red uced significantly after SLT (1.5 X 10(6) dynes/cm(2) pre-SLT to 1 X 1 0(5) dynes/cm(2) post-SLT; P=.01), but there was no change in the LV e lastic modulus. RV velocity of fractional shortening increased signifi cantly after SLT (0.23 pre-SLT to 0.58 post-SLT, P=.02), and RV ED and ES wall thicknesses revere 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-SL T, 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.