A system and method for designating between types of activation by a pulse generator configured to deliver a left ventricular (LV) pacing pulse at an LV pacing site as part of a cardiac resynchronization therapy (CRT) are provided. The system includes a sensing channel configured to collect cardiac activity (CA) signals along at least one sensing vector extending through a septal wall between the LV and right ventricle (RV). The CA signals are indicative of one or more beats and include a pre-LV pacing segment indicative of cardiac activity preceding the LV pacing pulse and a post-LV pacing segment indicative of cardiac activity following the LV pacing pulse. The system includes memory to store program instructions. One or more processors are configured to implement the program instructions to analyze the pre-LV pacing segment to identify a first myocardium activation (MA) characteristic of interest (COI). The system analyzes the post-LV pacing segment to a second MA COI, compares the first and second MA COI to first and second MA criteria, respectively, designates the CA signals to be indicative of one of a fusion beat, a capture beat or a pseudofusion beat based on the comparison of the first and second MA COI to first and second MA criteria and store a result of the designation.