“…13 Comparing RV to LV size for RV assessment is not an entirely new concept and has been applied for the assessment of RV size in pediatric patients using angiography. [14][15][16] In the PAH population, the RV end-diastolic dimension and RV end-diastolic area by echocardiography in the four-chamber view have been compared to LV and used to identify RV dilation using a normal ratio of 0.5-0.7, and 0.8-1.0, 1.1-1.4, and 1.5 as cutoffs for mild, moderate, and severe dilation, respectively. 17 Furthermore, RV/LV end-systolic diameter measured in the parasternal short-axis view by echocardiography correlates well with invasive hemodynamic measurements in children with PH and an RV/LV ratio >1 was associated with adverse outcomes.…”