Computer analysis of cardiac contractility variables obtained by M-mode echocardiography in normal newborns.

There are few echocardiographic studies which examine ventricular cavity and wall dimensions as well as ventricular function in normal newborn infants. We investigated the M-mode echocardiograms of 60 normal newborn infants aged 3 to 6 days using computer analysis. Using the same method, we examined in addition left ventricular cavity dimensions and contractility variables of 15 healthy newborn infants sequentially during the first hour of life. The left and right ventricular diameters, their systolic shortening fraction and maximal rate of change, as well as the thickness of the interventricular septum and the left ventricular posterior wall were found to be comparable to previously published values. In addition, we found that the left ventricular end-diastolic diameter and the systolic shortening fraction of the left ventricular diameter increase significantly during the first hour of life. This increase is probably because of the postnatal increase in left ventricular volume and pressure work.