Invited Lecture: Fetal cardiac function and circulatory dynamics—the impact of Doppler echocardiography

I N BUT A FEW YEARS, CLINICAL FETAL CARDIOLOGY HASbecome a well-established discipline of fetal medicine.This rapid development was essentially due to the advent of fetal echocardiography, combined with Doppler technology-techniques which gave clinicians and researchers the means to verify on humans the fundamental concepts of fetal circulatory physiology and pathophysiology that were based on the pioneer works performed mostly on fetal sheep.It is my intention to review these basic experimental concepts as they pertain to human ultrasonographic observations.The review will be divided into three parts.First, the contractile characteristics of the fetal myocardium will be briefly discussed, underscoring its reaction to changes in loading conditions.Second, fetal cardiac performance and circulatory dynamics will be considered.Third, the balance between fetal cephalic and subdiaphragmatic vascular impedances, as assessed by Doppler flow velocity waveforms through the aortic isthmus, will be addressed. Contractile characteristics of the fetal myocardium Myocardial contractilityBy definition, myocardial contractility is the intrinsic ability of muscle to generate force, independent of changes in preload, afterload and rate of contraction.When isolated fetal muscular strips are studied, the force generated by the fetal myocardium is consistently lower than that of the adult. 1 At all lengths along the length-tension curve, the active tension generated by t Lecture given to the Fetal Cardiology Working Group at the XXX