Figure 2.

SU5416-hypoxia (SuHx) rats develop significant right ventricular (RV) dysfunction before mineralocorticoid receptor antagonist treatment as determined by cardiac MRI. Representative long (A) and short (B) axis images of a normoxic control (CTRL) rat. In contrast, a long axis view of a SuHx rat reveals severe RV dilation and hypertrophy (C), whereas a short axis view demonstrates severe septal flattening (D). All images were taken at end-diastole. Quantification of ventricular function by cardiac MRI demonstrated a significant reduction in the RV ejection fraction (EF; E), whereas the left-ventricular (LV) EF (F) was significantly increased in all three groups of SuHx rats compared with CTRLs without a significant difference between the study groups prior to treatment (P ≥ 0.54 for each of the post hoc pairwise comparisons). Consistent with reduced RV function and impaired LV filling, the RV/LV end-diastolic volume (EDV; G) ratio was increased, whereas both the cardiac index (H) and stroke volume index (I) were reduced. There were no significant differences in RVEDV/LVEDV ratio, cardiac index, or stroke volume index between the three groups prior to treatment (P ≥ 0.20 for each of the post hoc pairwise comparisons). Data are presented as means ± SD of 4 healthy CTRLs and 13–15 animals per treatment group. One-way ANOVA was used to compare the four groups followed by post hoc Tukey’s test for pairwise contrasts. **P < 0.01, ***P < 0.001, ****P < 0.0001. EPL, eplerenone; PL, placebo; SPL, spironolactone.