A New Ultrasound Technique to Measure the Isovolumetric Contraction Time as an Index of Cardiac Contractility: Fetal Lamb Validation

Abstract

Objective: We developed a noninvasive Doppler technique for measuring fetal cardiac isovolumetric contraction time (ICT). The purpose of this study was to determine how well our method real cardiac performance using fetal lamb as an instrumented model.

Methods: The true ICT was measured by simultaneous recording of the pressure waves of the left ventricle and ascending aorta. The maximum first derivative of the left ventricular pressure wave (Max dp/dt) was calculated. The Doppler ICT was measured in the apporpriately filtered Doppler cardiac signals. Positive and negative inotropic agents were administered to change the cardiac contractility.

Results: There was an inverse relationship between the Doppler ICT and the Max dp/dt. Excellent linear correlation was found an absolute value and changes from control value between the true ICT and the Doppler ICT (r = 0.959, r = 0.62).

Conclusion: The Doppler ICT measurement provides useful information about changes in ventricular performance.

Keywords

Fetal cardiac isovolumetric contraction time Doppler ultrasound cardiac contractility

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