A method and a medical device for determining efficacy of a pulsed electric field (PEF) ablation procedure are disclosed. According to one aspect, the method includes generating at least one pulsed electric field (PEF) pulse to be delivered to at least one electrode of a plurality of electrodes, the at least one electrode being at a distal end of a PEF ablation catheter and being positionable in proximity to a target region of tissue to be ablated. The method also includes determining an index of completeness indicative of a completeness of ablation of the target region of tissue based at least in part on a change in a parameter compared to an expected change in the parameter, the change in the parameter being caused at least in part on an extent of ablation of the target region.