SPATIOTEMPORAL COMPLEXITY OF VENTRICULAR-FIBRILLATION REVEALED BY TISSUE MASS REDUCTION IN ISOLATED SWINE RIGHT VENTRICLE - FURTHER EVIDENCE FOR THE QUASI-PERIODIC ROUTE TO CHAOS HYPOTHESIS

We have presented evidence that ventricular fibrillation is determinis tic chaos arising from quasiperiodicity. The purpose of this study was to determine whether the transition from chaos (ventricular fibrillat ion, VF) to periodicity (ventricular tachycardia) through quasiperiodi city could be produced by the progressive reduction of tissue mass, In isolated and perfused swine right ventricular free wall, recording of single cell transmembrane potentials and simultaneous mapping (477 bi polar electrodes, 1.6 mm resolution) were performed, The tissue mass w as then progressively reduced by sequential cutting, All isolated tiss ues fibrillated spontaneously, The critical mass to sustain VF was 19. 9 +/- 4.2 g, As tissue mass was decreased, the number of wave fronts d ecreased, the life-span of reentrant wave fronts increased, and the cy cle length, the diastolic interval, and the duration of action potenti al lengthened, There was a parallel decrease in the dynamical complexi ty of VF as measured by Kolmogorov entropy and Poincare plots. A perio d of quasiperiodicity became more evident before the conversion from V F (chaos) to a more regular arrhythmia (periodicity), In conclusion, a decrease in the number of wave fronts in ventricular fibrillation by tissue mass reduction causes a transition from chaotic to periodic dyn amics via the quasiperiodic route.