Fetal aortic distension waveforms for evaluating cardiac function and changes in blood pressure: Fetal lamb validation

Abstract

To investigate which part of the fetal aortic distension waveform is mainly influenced by changes in fetal cardiac contractility and aortic blood pressure. In acute preparation, aortic distension waveforms were recorded using an echo-tracking system, and aortic and left ventricular pressure waveforms were obtained from six late-gestation catheterized fetal lambs. Dobutamine and angiotensin II were separately infused and the correlations between the maximum value in the first derivative of left ventricle pressure waveforms (Max dP/dt) and fetal blood pressure, and the parameters obtained from aortic distension waveforms were analyzed using linear regression analysis. With a change in cardiac contractility, the maximum value of first derivative of the systolic rising slope in the aortic distension waveform had a positive correlation with Max dP/dt (r = 0.93, P < 0.0001). With changes in fetal blood pressure, both the amplitude and the ratio of increase from the end diastolic diameter obtained from the aortic distension waveform had a significant positive correlation with aortic blood pressure amplitude (r = 0.60, P < 0.01; r = 0.61, P < 0.01, respectively). The maximum first derivative of the systolic rising slope in the aortic distension waveform and the amplitude in the aortic distension waveform enable us to non-invasively substitute for fetal cardiac contractility and aortic blood pressure amplitude, respectively.