extra-systole

(eks-trah-sis'to-le). The premature contraction of one or more chambers of the heart, the fundamental rhythm of the cardiac action being maintained, auric'ular e.-s., premature contraction of an auricle, inter'polated e.-s., a contraction occurring between two normal beats of the heart, no'dal e.-s., a prematiire contraction of both chambers together of one side of the heart, ventrjc'ular e.-s., premature contraction of the ventricle.