Click on image to view larger version.

Figure 1 (Top) Ventricular activation sequence using three-dimensional noncontact mapping (EnSite 3000, Endocardial Solutions, Minneapolis, Minnesota) in a patient with dilated (non-ischemic) cardiomyopathy (left ventricular [LV] ejection fraction [EF] 30%, New York Heart Association [NYHA] functional class III) with a QRS duration of 154 ms who responded to cardiac resynchronization therapy (CRT). The propagation wavefront splits when encountering a conduction block located at the LV anterior wall, resulting in delayed activation of the lateral wall. (Bottom) The virtual electrograms over the line of block are displayed. Note the fragmented or double potential electrograms. The LV lead was positioned at the basal lateral region of LV (white arrow, top). One year after CRT, the LVEF was 42%, and the patient was in NYHA functional class I. LAT = lateral.