Echocardiographic systolic time intervals in premature infants with patent ductus arteriosus

Thirty-six premature infants with respiratory distress syndrome and clinically significant patent ductus arteriosus (PDA) were studied by M-mode echocardiography before and after closure of the ductus. Before closure the ratio of left ventricular preejection period to left ventricular ejection time (LPEP/LVET) was .26±.03 (mean±SD). After closure of the ductus, LPEP/LVET was .38±.04 (mean±SD), significantly different from the value before closure but not significantly different from the value found in 21 control infants; also, a ratio < .30 was always associated with a clinically significant shunt. The combination of systolic time interval measurement with standard M-mode measurement of the left side of the heart enhanced echocardiographic detection of PDA in our series. Serial evaluation of systolic time interval measurements may provide a further index of left-to-right shunt through a PDA and be a valuable adjunct to the clinical management of these patients.