DOPPLER ECHOCARDIOGRAPHY Detection and quantitation of constriction of the fetal ductus arteriosus by Doppler echocardiography

Pulmonary hypertension may occur in the fetus in the presence of constriction of the ductus arteriosus. The feasibility of detection and quantitation of fetal ductal constriction by Doppler echocardiography was assessed in an animal preparation in which ductal constriction was created in the fetal lamb with a variable ligature causing varying degrees of fetal pulmonary hypertension (fetal pulmonary arterial systolic pressure 57 to 97 mm Hg and ductal gradient 9 to 42 mm Hg). Comparison of blinded, continuous-wave peak Doppler velocity (V) measurements of the ductal gradient with the modified Bernoulli assumption (gradient 4V2) compared well with direct catheter measurements of instantaneous peak systolic gradient (r = .99, catheter = 0.95 x Doppler + 0.6), peak-to-peak gradient (r = .97), and mid-diastolic gradient (r = .85). Ductal constriction was characterized by an increase in the peak systolic and diastolic velocities. The normal human fetal ductus arteriosus blood flow velocity pattern was assessed by pulsed Doppler techniques in 25 normal human fetuses after 20 weeks gestation. The peak systolic flow velocity in the ductus arteriosus measured by image-directed pulsed Doppler echocardiography ranged from 50 to 141 cm/sec (mean 80 cm/sec) and increased with gestational age (r = .50). Diastolic velocity in the ductus arteriosus was consistently directed toward the descending aorta and ranged from 6 to 30 cm/sec. The ductal systolic velocities were the highest blood flow velocities in the fetal cardiovascular system. Application of these techniques to fetuses whose mothers were receiving indomethacin for treatment of premature labor at 30 to 31 weeks gestation confirmed this method to be sensitive for detection of fetal ductal constriction, which developed in three fetuses. Doppler echocardiography can be used to assess the flow velocity in the fetal ductus in humans and to detect constriction and a pressure gradient across it. Quantitation of fetal ductal gradient is possible and may be useful for assessment of the severity of fetal ductal constriction in such patients. Circulation 75, No. 2, 406-412, 1987. THERE IS EVIDENCE from animal experiments in the fetal lamb that constriction of the ductus arteriosus by a prostaglandin inhibitor can cause fetal pulmonary hypertension and pulmonary arteriolar changes. I 2The administration of a prostaglandin inhibitor in late gestation has been associated with persistent neonatal pulFrom the Lillie Frank Abercrombie Section of Cardiology and the Section of Neonatology, Department of Pediatrics, and the Department of Obstetrics and Gynecology, Division of Maternal-Fetal Medicine, Baylor College of Medicine, and Texas Children's Hospital and Jefferson Davis Hospital, Houston. Address for correspondence: James C. Huhta, M.D., Pediatric Cardiology, 1-253, Texas Children's Hospital, 6621 Fannin, Houston, TX 77030. Received Sept. 9, 1986; revision accepted Nov. 6, 1986. Dr. Huhta was supported by New Investigator Award HL3 1153 from the NIH Public Health Service, Bethesda, and grant No. G-410 from the American Heart Association, Texas Affiliate. 406 monary hypertension and there is evidence that other forms of perinatal asphyxia may be related to chronic prenatal ductal constriction and pulmonary vascular changes .-5 A method for the detection and quantitation of fetal ductal constriction would be useful in the prenatal management of such fetuses. It has been shown that the human fetal ductus can be imaged after 20 weeks gestation.6 However, a widely applicable method for ductal assessment should yield information concerning the hemodynamic significance of ductal changes. We attempted to combine observations in animals and man to answer two questions: (1) Can the pattern of blood flow velocity in the fetal ductus as determined by Doppler techniques be used for the detection of fetal ductal constriction? (2) Can CIRCULATION by gest on N ovem er 8, 2017 http://ciajournals.org/ D ow nladed from DIAGNOSTIC METHODS-DOPPLER ECHOCARDIOGRAPHY the severity of fetal ductal constriction be estimated noninvasively?