CARDIAC REGRESSION SEQUENCE - REVERSAL OF BLOOD-FLOW IS DIAGNOSTIC BUT NOT CAUSATIVE IN AN ACARDIAC FETUS

In 1% of monozygotic twin pregnancies, one fetus is without a heart; b lood circulation is maintained by an accompanying ''pump'' twin. Such an acardiac condition is usually diagnosed on the basis of further mal formations visible by ultrasonography. We describe a monoamniotic twin pregnancy with early growth reduction in one twin. His skeleton and t he shape of the body including the head were normal; however, heart, l ungs and liver were absent. ''Death of one twin'' had thus been the di agnosis before termination of pregnancy. Studies of the blood flow in acardiac fetuses by several investigators have shown that perfusion of a heartless fetus is opposite to the normal direction and the term '' twin reversed arterial perfusion sequence'' has been proposed. While ' 'reversed arterial perfusion'' might be a key diagnostic element for t he ultrasonographic examination of the acardiac condition, it need not necessarily be the primary cause. A lethal defect in early heart deve lopment is much more likely to be the primary event which is temporari ly rescued by the presence of the accompanying ''pump'' twin. A term l ike ''cardiac regression sequence'' would be much better suited to des cribe the condition. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.