SIMULATED EPICARDIAL POTENTIAL MAPS DURING PACED ACTIVATION REFLECT MYOCARDIAL FIBROUS STRUCTURE

Using a three-dimensional propagation model of the human ventricular m yocardium, we studied the role of fibrous structure in generating epic ardial potential maps. This model represents the myocardium as an anis otropic bidomain with an equal anisotropy ratio, and it incorporates a realistic representation of anatomical features, including epi-endoca rdial fiber rotation in the compact portion of the wall (compacta) and a distinct fiber arrangement of the trabeculated portion (trabeculata ). Activation sequences were elicited at various intramural depths, an d maps were calculated throughout a 60 ms sequence. The simulated maps closely resembled those measured by others in the canine heart. Durin g the early stages of activation, a typical map featuring a central mi nimum flanked by two maxima emerged, with the axis joining these extre ma approximately parallel to the fibers near the pacing site, and the axis joining the maxima rotated in the same direction as the fibers fo r different pacing depths; for endocardial and subendocardial pacing t his map changed into one with an oblong positive area. During the late r stages of activation, the positive areas of the maps expanded and ro tated with the transmural fiber rotation. In concurrence with experime nts, we saw a fragmentation and asymmetry of expanding and rotating po sitive areas. The latter features-apparently caused by the interface b etween the compacta and trabeculata, variable local thickness of the w all, or local undulations of the vetricular surface-could not be repro duced by more idealized, slab models. (C) 1998 Biomedical Engineering Society. [S0090-6964(98)00706-1].