An exemplary method includes delivering a cardiac pacing therapy that includes an atrio-ventricular delay and an interventricular delay, providing a paced propagation delay associated with delivery of a stimulus to a ventricle, delivering a stimulus to the ventricle, sensing an event in the other ventricle caused by the stimulus, determining an interventricular conduction delay value based on the delivering and the sensing, determining a interventricular delay (ΔSur) based on the interventricular conduction delay and the paced propagation delay and determining an atrio-ventricular delay based at least in part on the interventricular delay (ΔSur). Other exemplary methods, devices, systems, etc., are also disclosed.