Fibrillation is more complex in the left ventricle than in the right ventricle

Introduction: The mechanisms that maintain ventricular fibrillation (VF) ar e not completely understood. It has been proposed that increased ventricula r wall thickness destabilizes VF wavefronts and therefore is an important d eterminant of VF activation patterns, We hypothesized that if this is the c ase, then VP patterns on the thin-walled right ventricle (RV) should be sim pler than those on the thick-walled left ventricle (LV). Methods and Results: In seven open chest pigs, we mapped VF simultaneously from tao epicardial recording arrays, one on the RV and one on the LV. Each array contained 504 unipolar electrodes (in a 21 x 24 grid) spaced by 2 mm , We used specialized pattern analysis methods to compute quantitative desc riptors of RV and LV activation patterns, Our data show that VF is more org anized in the RV than the LV, containing fewer, larger wavefronts that foll ow fewer distinct pathways and are less likely to fragment or collide with other wavefronts. The incidence, size, and cycle length of reentrant circui ts were similar in the two ventricles, but RV reentry persisted for more cy cles, These results are not predicted by the differences in electrophysiolo gic properties between LV and RV that have been reported in mammalian heart s. Conclusion: The geometry of the ventricular wall, particularly wall thickne ss, is an important determinant of VF activation patterns.