Among 45 CpcPH/heart failure with preserved ejection fraction participants, 11 with normal left atrium (compared to 34 with abnormal left atrium, p < 0.05 for all) had low left ventricle (LV) transmural pressure (2.9 ± 2.4 vs. 6.2 ± 2.9 mmHg), and increased right ventricle (RV):LV ratio (2.41 ± 1.09 vs. 1.46 ± 0.66) and interventricular septal angle (149 ± 8 vs. 136 ± 10), indicating exaggerated ventricular interdependence from a dilated RV.