Methods for ablating tissue in a patient having atrial fibrillation comprise advancing an elongate flexible shaft through a patient's vasculature into a chamber of a heart. The elongate flexible shaft has an energy source and a sensor. Tissue in the heart is scanned with the sensor and data about the tissue is captured. The captured data is grouped into one of a plurality of tissue classifications and an anatomical map of the tissue showing the grouped data is displayed. At least a portion of the tissue is ablated so as to form a conduction block that blocks aberrant electrical pathways in the heart. The ablated tissue is grouped into one or more predefined tissue classifications during or prior to the ablation.