Videodensitometry of the margins of the fluoroscopic image of the left ventricle (LV) was used to evaluate LV wall motion. Differentiation of the wall motion signal reflected the velocity of LV contraction (dv/dt) during various inotropic interventions in 6 anesthetized dogs. Alterations in dv/dt were similar to changes in simultaneously measured LV peak dP/dt and the quotient of dP/dt and developed LV pressure, two widely accepted parameters of LV contractile state.