A new ultrasound technique to measure the isovolumetric contraction time as an index of cardiac contractility: fetal lamb validation.
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 reflects 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 appropriately 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 = 0.962).


CONCLUSIONS
The Doppler ICT measurement provides useful information about changes in ventricular performance.
Koga
Tsuyoshi
T
Department of Obstetrics and Gynaecology, University of Sydney at Westmead Hospital, Westmead, New South Wales, Australia. osannoie@dream.com
Athayde
Neil
N
Trudinger
Brian
B
D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000818:Animals; D001011:Aorta / Q000502:physiology; D001784:Blood Gas Analysis; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D002316:Cardiotonic Agents / Q000494:pharmacology; D004298:Dopamine / Q000494:pharmacology; D015150:Echocardiography, Doppler / Q000379:methods*; D005260:Female; D006321:Heart / Q000196:embryology / Q000502:physiology*; D006340:Heart Rate, Fetal / Q000187:drug effects / Q000502:physiology; D009200:Myocardial Contraction / Q000502:physiology*; D011247:Pregnancy; D011412:Propanolamines / Q000494:pharmacology; D012044:Regression Analysis; D012756:Sheep / Q000196:embryology*; D016216:Ultrasonography, Prenatal / Q000379:methods*; D016276:Ventricular Function; D016277:Ventricular Function, Left / Q000502:physiology; D017725:Ventricular Pressure / Q000502:physiology
D000319:Adrenergic beta-Antagonists; D002316:Cardiotonic Agents; D011412:Propanolamines; C036604:esmolol; D004298:Dopamine