idioventricular

adjective

id·​io·​ven·​tric·​u·​lar ˌid-ē-ə-ven-ˈtrik-yə-lər, -vən- 

: of, relating to, associated with, or arising in the ventricles of the heart independently of the atria

apparent accelerated idioventricular rhythm occurred in one patient

—T. J. Sullivan