Quantitative Functional Cardiac Magnetic Resonance Imaging in Mice with Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a condition characterized by elevated mean pulmonary artery pressure, pulmonary vascular remodeling and secondary right heart failure. Mouse models are instrumental in understanding the pathophysiology of PAH and require precise methods to non-invasively and longitudinally evaluate in vivo cardiac morphology and function. In this study we used magnetic resonance imaging (MRI) to measure in vivo cardiac dimensions in mice with PAH. PAH was induced in C57BL/6 mice using 10% hypoxia and weekly, subcutaneous injections of 20 mg/kg of SU5416 for three weeks. Short axis images at 1 mm intervals from the base to the apex of the heart were collected by proton MRI with a fast low angle SHot (FLASH)-cine sequence, TE: 2.11 ms and TR: 8 ms. Thirteen images were collected throughout each cardiac cycle. Measurements are presented of right ventricle (RV) lateral wall thickness and ejection fraction. RV wall thickness at the uppermost region of the ventricle was greater in PAH mice than control at end-diastole (control, 0.30 + 0.05 mm, PAH; 0.48 + 0.06 mm, p< 0.01, n=6) but not different at end-systole (control, 0.59 + 0.11 mm; PAH, 0.70 + 0.11 mm, n=6). RV ejection fraction was decreased in PAH mice (control, 71.9% + 2.5, PAH 57.6% + 5.4, p=0.04, n=6). These data demonstrate that MR imaging can detect right ventricle remodeling and cardiac dysfunction under in vivo conditions.