Estimation of pulmonary/systemic resistance ratios from echocardiographic systolic time intervals in young patients with congenital or acquired heart disease

Previous work has shown the positive correlation of echocardiographic right ventricular preejection period/right ventricular ejection time ratio ($\text{RPEP}\text{RVET}$) with pulmonary vascular resistance and pulmonary arterial diastolic pressure obtained at cardiac catheterization. However, the correlation was insufficient to predict pulmonary arterial diastolic pressure or vascular resistance from a given $\text{RPEP}\text{RVET}$ ratio. In this study the $\text{RPEP}\text{RVET}$ ratio was compared with left ventricular preejection period/ejection time ratio ($\text{LVEP}\text{LVET}$) in 25 patients undergoing cardiac catheterization, and a strong correlation was found between the ratio $\text{(}\text{RPEP}\text{RVET}\text{)}\text{(}\text{LPEP}\text{LVET}\text{)}\text{=}\text{R}\text{L}$ and the ratio of pulmonary arteriolar resistance/systemic arteriolar resistance ($\text{PAR}\text{RS}$), especially when $\text{R}\text{L}$ was correlated with $\text{log}{}_{10}\text{PAR}\text{RS}$ (r = 0.902). A very high correlation (r = 0.960) was found between $\text{R}\text{L}$ and $\text{log}{}_{10}\text{PAR}\text{RS}$ when the group was restricted to patients with a ventricular septal defect or a complete endocardial cushion defect. Regression equations for prediction of $\text{PAR}\text{RS}$ have been derived for the various groups.