A twin without a heart, parasitic on, or utilizing the placental circulation of, its mate. ... (05 Mar 2000) ... 
(a-kahr´de-әs) a parasitic twin fetus that lacks a heart and uses the circulation of its twin. See also hemiacardius and holoacardius.
Type: Term Pronunciation: ā-kar′dē-ŭs Definitions: 1. A twin without a heart that remains viable by using the placental circulation of its mate; usually other body parts are also absent.