MRI for Cardiac Evaluation of Pulmonary Hypertension in Rats

Rat models of pulmonary hypertension (PH) are usually evaluated using echocardiography (echo), and/or terminal hemodynamic measurements, morphological analysis and histology. Unfortunately, right ventricular (RV) structure and function cannot be easily assessed by echo. We evaluated noninvasive MRI to obtain RV mass, wall thickness and ejection fraction. Study rats (n=27) received varied monocrotaline doses to induce PH while a control group received PBS (n=5). MRI, echo, and hemodynamic evaluations were done 4 weeks post‐injection, followed by necropsy. The results show that peak PA pressure correlated with MRI derived RV mass (r= 0.49), EF (r= −0.47), RV wall thickness (r=0.59), and with echo derived myocardial performance index (MPI) (r=0.48) and PA acceleration time (r= −0.57). MRI derived RV mass and RV:LV mass ratio correlated respectively with necropsy RV mass (r=0.69) and RV:LV mass ratio (r=0.57). Echo derived MPI also correlated with MRI derived RV EF (r= −0.66). Peak PA pressure however did not correlate with echo derived RV wall thickness or RV ejection time. This suggests Doppler derived indices (MPI) from echo do not provide a good assessment of RV size and function. The data demonstrate the importance of MRI in evaluating RV structure and function in rat models of PH.