Noninvasive measurement of isovolumetric contraction time during hypoxemia and acidemia: Fetal lamb validation as an index of cardiac contractility

Abstract

Objectives The objectives of this study are firstly to clarify how the Doppler isovolumetric contraction time (ICT) is influenced by arterial oxygen pressure (PaO 2) or pH, and secondly to confirm the relationship between the Doppler ICT and myocardial contractility during hypoxemia and/or acidemia in the fetal lamb. Material and methods In 12 pregnant ewes, fetal hypoxemia and acidemia were induced by giving ewes a variable mixture of gases for 120 min. The chronological change of fetal PaO 2, pH, Doppler ICT and maximum first derivative of the left ventricular pressure waveform (Max d p/d t) was recorded every 30 min. Results Doppler ICT and PaO 2 had no significant regression. On the other hand, Doppler ICT and pH demonstrated a significant negative regression. Moreover, one critical given pH point was indicated with statistical significance at 7.20 and the prolongation of the Doppler ICT was found more markedly in the range below the pH of 7.20 compared with the range above 7.20. A significant negative linear regression was found between the Doppler ICT and the Max d p/d t. Conclusion The measurement of Doppler ICT enables us to predict severe acidosis and a decrease of myocardial contractility in the fetus.