Intrauterine thrombosis of the arterial duct

Abstract

A hydropic neonate, born at 28 weeks gestation, died 45 minutes after birth. Autopsy showed an abnormally long and tortuous arterial duct which was occluded by laminated thrombus. The right heart chambers and the left ventricle were dilated, but there was no other structural cardiac abnormality. Apart from the abnormal ductal morphology, there was no evident cause for the intrauterine thrombosis of the arterial duct, which appeared to be the sole cause of fatal heart failure.A NTENATAL ABNORMALITIES OF THE ARTERIAL DUCT are rare. The duct may be completely absent due to failure of development, or premature ductal closure may occur as a result of muscular constriction of the duct wall, usually a fatal event. We report a case of fetal hydrops followed by premature delivery and death due to thrombotic occlusion of an abnormally tortuous arterial duct. Case reportAn 18-year-old primigravida presented with premature labor at 28 weeks of pregnancy. Ultrasound scan of the fetus had been normal at 18 weeks gestation. Despite treatment with ritodrine and intramuscular dexamethasone, labor progressed to result in breech delivery of a male infant weighing 1380 gm with apgar scores of two at both one and five minutes. The baby died 45 minutes after delivery despite intensive resuscitative measures.Autopsy showed usual arrangement of the organs and atriums ("solitus") with normal systemic and pulmonary venous connections, an enlarged heart, very dilated right atrium, a large patent oval foramen, marked dilatation of the right ventricle, moderate dilatation of the left atrium and a slightly dilated left ventricle. The relationship and the morphology of the great arteries and their branches were normal but the aortic arch was slightly displaced medially by an unusually long and tortuous duct which lay alongside it. The duct was completely occluded by laminated thrombus but there was no evidence of ductal constriction. DiscussionThe fetal arterial duct is usually a short, wide vessel which plays a vital role in bypassing the high resistance circulation of the non-functioning lungs. The fetal right ventricle normally contributes about two-thirds of the total cardiac output, most of this crossing the arterial duct to provide about 85% of descending aortic flow, only about 10% of the output of the right ventricle being directed to the lungs.' Inability to shunt right-toleft across the duct during fetal life might, therefore, be expected to cause major hemodynamic upset with pressure overload of the right ventricle and volume overload of the left ventricle due to an inevitable substantial increase in right-to-left shunting across the oval foramen. 2,3Absence of development of the arterial duct may occur as a very rare anomaly without apparent untoward effects on fetal circulation if it is associated with other cardiac anomalies such as tetralogy of Fallot or common arterial trunk 1 which allow right to left shunting to take place at ventricular level rather than across the arterial duct. Absence of development of the duct