Department of Obstetrics and Gynecology of Santa Casa Charity Hospital, Belo Horizonte, Minas Gerais, Brazil. Av. Francisco Sales 1800, Belo Horizonte, MG â€“Brazil.
Synonyms: TRAP sequence, acardia anomaly, hemiacardius (imperfectly formed heart), holoacardius (absence of heart), acardiac acephalus, acardius amorphous, acadius acormus, acardius anceps, acardius myelacephalus.
Definition: Rare anomaly in which one twin has an absent, rudimentary, or nonfunctioning heart. Twin pregnancy with acardiac results from an artery-to-artery placental anastomosis in which the pump twin, morphologically normal, perfuses the abnormal acardiac in a reversed circulation.
Case report: A-20-year-old G2,P0,A1 was referred at 24 weeks gestation with a history of twin gestation associated with polyhydramnios. The ultrasound revealed twins, monochorionic monoamniotic, with one twin appeared normal and a second twin with significant subcutaneous edema, with no evidence of cephalic pole and superior limbs; primitive thorax without pulmonary tissue clearly demonstrable and absence of cardiac chambers. The inferior limbs were observed entirely and the spinal column was present only in the sacral segment and the last four lumbar vertebrae. The bladder and kidneys were present. The umbilical cord presented a single umbilical artery. Doppler velocimetry showed increased resistance to blood flow in the umbilical artery of both fetuses. Prophylactic digitalization to try to prevent cardiac failure in the normal twin was tried.
With 31 weeks of gestation the ultrasound exam showed hepatomegaly and enlarged cardiomegaly in twin 1 with discrete pulmonary stenosis. Due to aggravation of twin 1, the parents were advised about the risks and benefits of an invasive procedure and intrauterine embolization procedure was performed by insertion of absolute alcohol in the perivascular region of the umbilical artery. An ultrasound carried out 24 hours after the interruption procedure verified a reduction in the congestion of the umbilical cord of twin 1. The arterial flow in the acardiac fetus remained occluded. Membrane rupture occurred two days after embolization and cesarean section procedure was done and a newborn male, Apgar 9/9, weighing 1515 grams was born. There was cardiomegaly regression and the infant was discharged in his 33rd day of life.
The anatomopathologic study of twin 1 revealed acardiac-acephalo fetus formed by a hemorrhagic tissue mass weighing 400 grams. The superior portion ended in a friable mass without subjacent osseous structure. The superior limbs were absent and the inferior ones were curved with four fingers in each foot. The internal organs exam revealed absence of heart, major vessels, lungs, liver, pancreas and superior gastrointestinal tract. The kidneys, suprarenal and bladder were observed in their usual positions. Radiography showed abnormal characteristics of the skeleton superior pole. Placental study revealed velamentous insertion of the umbilical cord of the acardiac fetus which presented two vessels. Vascular anastomosis was identified over corial disk.