title: 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 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.
authors.affiliation: Department of Obstetrics and Gynaecology, University of Sydney at Westmead Hospital, Westmead, New South Wales, Australia. osannoie@dream.com
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Koga
authors.forename: Neil
authors.initials: N
authors.lastname: Athayde
authors.forename: Brian
authors.initials: B
authors.lastname: Trudinger
mesh_terms: 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
chemical_list: D000319:Adrenergic beta-Antagonists; D002316:Cardiotonic Agents; D011412:Propanolamines; C036604:esmolol; D004298:Dopamine