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; blood circulation is maintained by an accompanying "pump" twin. Such an acardiac condition is usually diagnosed on the basis of further malformations visible by ultrasonography. We describe a monoamniotic twin pregnancy with early growth reduction in one twin. His skeleton and the shape of the body including the head were normal; however, heart, lungs and liver were absent. "Death of one twin" had thus been the diagnosis 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 the ultrasonographic examination of the acardiac condition, it need not necessarily be the primary cause. A lethal defect in early heart development is much more likely to be the primary event which is temporarily rescued by the presence of the accompanying "pump" twin. A term like "cardiac regression sequence" would be much better suited to describe the condition.
Ersch
J
J
Department of Pathology, University Hospital Zurich, Switzerland.
Stallmach
T
T
D000015:Abnormalities, Multiple; D000028:Abortion, Induced; D000328:Adult; D005260:Female; D006330:Heart Defects, Congenital; D006801:Humans; D011247:Pregnancy; D014430:Twins, Monozygotic