Background: Combined pre- and post-capillary pulmonary hypertension (Cpc-PH) has overlapping pathophysiology due to left heart disease and pulmonary vascular disease, which may vary in an individual patient. Hypothesis: While the majority of CpcPH patients have left heart disease with abnormal left atrium, a minority of CpcPH patients have normal left atrium and develop elevated left-sided pressures due to exaggerated ventricular interdependence and pericardial restraint. Aim: to define ventricular interdependent sub-phenotype of CpcPH. Methods: 30 CpcPH patients undergoing invasive cardiopulmonary exercise test with complete echocardiographic data were identified. Abnormal left atrium group was defined as left atrial volume index ≥40mL/m 2 and E/E' ≥10, and rest was defined as normal left atrium group. p-value <0.05* Results: Key metrics of abnormal (n=23) vs normal (n=7) left atrium subjects are shown in Figure. In the same order (abnormal vs normal), age was 65±15 vs 61±16, female gender 6 (26%) vs 4 (57%), BMI 34±8 vs 38±10, H2FpEF score 5.8±2.3 vs 5.3±1.7, BNP 514±406 vs 191±280, eccentricity index 1.12±0.25 vs 1.24±0.38, RV:LV ratio 0.9±0.3 vs 0.9±0.2, E' medial 5.6±1.7 vs 9.7±4.0*, E' lateral 6.8±2.2 vs 9.2±1.9*, TAPSE/PASP 0.33±0.12 vs 0.41±0.18, epicardial fat 6±2 vs 6±3, delta ETCO 2 -1.9±2.0 vs +1.7±2.1. Rest hemodynamics: mPAP 42±6 vs 37±11, PAWP 21±3 vs 18±3*, CO 4.9±1.4 vs 5.4±0.8, PVR 4.6±2.2 vs 3.4±1.5. With exercise: mPAP/CO slope 9.2±6.5 vs 6.1±4.5 and PVR 3.8±2.5 vs 2.7±1.2. Comorbidity burden between the two groups did not have a statistically significant difference. On one-year follow-up, incidence of mortality and heart failure hospitalizations were: 16 (69%) vs 1 (14%)*. Conclusions: A subset of CpcPH with normal left atrium have increased pericardial restraint and lower left ventricular transmural pressure. This likely leads to LV compression and Cpc-PH physiology. This sub-cohort has better exercise capacity and clinical outcomes.