Catheter ablation of ventricular tachycardia (VT) during sinus rhythm often relies on isochronal late activation mapping (ILAM), a validated means of isthmus identification, whereby points are binned by local activation time (LAT) into 8 isochrones, and isthmus regions are identified as regions with isochronal crowding. The resulting output, however, is inherently discretized and loss of LAT data occurs. To improve the precision of isthmus identification, we quantify isochronal density and assess the effect of increasing the number of isochrones used and the effectiveness of continuous metrics analogous to ILAM. To determine if current practices in ILAM calculation are optimized for isthmus detection. Patients undergoing VT ablation were included if high-density maps in both VT and sinus/paced rhythms were available. Isochronal density was assessed at differing numbers of isochrones, and isthmus discrimination was assessed. Continuous metrics that mimicked ILAM by assessing the local distribution of LAT values-using interquartile range (IQR) or the median absolute deviation (MAD)-were also defined and assessed. Eight electroanatomic maps (EAMs) were included. Isthmus discrimination improved progressively from a minimum AUC of 0.600 when assessing the isochronal density of 8-isochrone EAMs, to a maximum of 0.776 when assessing the density of 1000-isochrone EAMs (DeLong test, p<0.0001). On logistic regression, the continuous metrics using IQR (AUC = 0.714) and MAD (AUC = 0.721) both better discriminated isthmus identity than ILAM. Using more isochrones or using continuous ILAM analogs improves isthmus identification. By retaining more data, these metrics could increase the precision of VT ablation.