Ventricular ectopics The beat is caused by the premature contraction of a muscle within the ventricular myocardium [maiEuskB:di Em]n.心肌 (层)Ventricular ectopics The beat is caused by the premature contraction of a muscle within the ventricular myocardium [maiEu5kB:di Em]n. 心肌 ( 层)