isovolumetric

adjective

iso·​vol·​u·​met·​ric ˌī-sə-ˌväl-yu̇-ˈme-trik 

: of, relating to, or characterized by unchanging volume

especially : relating to or being an early phase of ventricular systole in which the cardiac muscle exerts increasing pressure on the contents of the ventricle without significant change in the muscle fiber length and the ventricular volume remains constant