Effects of dobutamine on left ventricular performance in newborns as determined by systolic time intervals.

To evaluate the effects of dobutamine on myocardial function in newborns, left ventricular systolic time intervals (STI) - normalized pre-ejection period (PEPI), normalized left ventricular ejection time (LVETI) and pre-ejection period to left ventricular ejection time ratio (PEP/LVET) - were assessed by echocardiography in 18 newborns treated with dobutamine for clinically diagnosed heart failure. Examinations were performed prior to and 30 min after starting dobutamine infusion (7.5 or 10 micrograms/kg per min). Patients were assigned to two groups according to their PEP/LVET prior to dobutamine administration: group I (n = 9) with pre-treatment PEP/LVET less than or equal to 0.35 and group II (n = 9) with pre-treatment PEP/LVET greater than 0.35. While there was no change of STI in group I, dobutamine infusion resulted in a significant decrease in PEPI (from 102 +/- 4.8 to 87.8 +/- 4.2; mean +/- SEM; P less than 0.01) and of PEP/LVET (from 0.56 +/- 0.05 to 0.45 +/- 0.05; mean +/- SEM; P less than 0.01) and in a significant increase of LVETI (from 237.6 +/- 5.6 to 253.3 +/- 5.2; mean +/- SEM; P less than 0.01) in group II. Heart rate increased significantly in both groups. Left ventricular end-diastolic dimension, also assessed by echocardiography, did not change in the eight studies performed. An increase in mean arterial pressure was found in three out of five newborns of group II and in one out of four patients in group I. It is concluded that dobutamine can improve cardiac performance in newborns with impaired left ventricular function. This effect is probably due to an improvement in myocardial contractility.