Virtual electrodes and deexcitation: New insights into fibrillation induction and defibrillation

Deexcitation During Fibrillation Induction and Defibrillation. Previous mod els of fibrillation induction and defibrillation stressed the contribution of depolarization during the response of the heart to a shock. This article reviews recent evidence suggesting that comprehending the role of negative polarization (hyperpolarization) also is crucial for understanding the res ponse to a shock, Negative polarization can "deexcite" cardiac cells, creat ing regions of excitable tissue through which wavefronts can propagate, The se wavefronts can result in new reentrant circuits, inducing fibrillation o r causing defibrillation to fail, In addition, deexcitation can lead to rap id propagation through newly excitable regions, resulting in the eliminatio n of excitable gaps soon after the shock and causing defibrillation to succ eed.