CHARACTERISTICS OF WAVE-FRONTS DURING VENTRICULAR-FIBRILLATION IN HUMAN HEARTS WITH DILATED CARDIOMYOPATHY - ROLE OF INCREASED FIBROSIS IN THE GENERATION OF REENTRY

Objectives. We sought to evaluate the characteristics of wave fronts d uring ventricular fibrillation (VF) in human hearts with dilated cardi omyopathy (DCM) and to determine the role of increased fibrosis in the generation of reentry during VF. Background. The role of increased fi brosis in reentry formation during human VF is unclear. Methods. Five hearts from transplant recipients with DCM were supported by Langendor ff perfusion and were mapped during VF. A plaque electrode array,vith 477 bipolar electrodes (1.6-mm resolution) was used for epicardial map ping. In heart no. 5, we also used 440 transmural bipolar recordings. Each mapped area was analyzed histologically. Results. Fifteen runs of VF (8 s/run) recorded from the epicardium were analyzed, and 55 episo des of reentry were observed. The life span of reentry was short (one to four cycles), and the mean cycle length was 172 +/- 24 ms. In heart no. 5, transmural scroll waves were demonstrated. The most common mod e of initiation of reentry was epicardial breakthrough, followed by a line of conduction block parallel to the epicardial fiber orientation (34 [62%] of 55 episodes). In the areas with lines of block, histologi c examination showed significant fibrosis separating the epicardial mu scle fibers and bundles along the longitudinal axis of fiber orientati on. The mean percent fibrous tissue in these areas (n = 20) was signif icantly higher than that in the areas without block (n = 28) (24 +/- 7 .5% vs. 10 +/- 3.8%, p < 0.0001). Conclusions. In human hearts with DC M, epicardial reentrant wave fronts and transmural scroll waves were p resent during VF. Increased fibrosis provides; a site for conduction b lock, leading to the continuous generation of reentry.