Mechanism for amplitude alternans in electrocardiograms and the initiation of spatiotemporal chaos

TitleMechanism for amplitude alternans in electrocardiograms and the initiation of spatiotemporal chaos
Publication TypeJournal Article
Year of Publication2017
AuthorsChen, Diandian Diana, Gray Richard A., Uzelac Ilija, Herndon Conner, and Fenton Flavio H.
JournalPhysical Review Letters
Volume118
Pagination168101
Abstract

It is widely believed that one major life-threatening transition to chaotic fibrillation occurs via spiral-wave breakup that is preceded by spatiotemporal dispersion of refractoriness due to alternations in the duration of the cardiac action potential (AP). However, recent clinical and experimental evidence suggests that other characteristics of the AP may contribute to, and perhaps drive, this dangerous dynamical instability. To identify the relative roles of AP characteristics, we performed experiments in rabbit hearts under conditions to minimize AP duration dynamics which unmasked pronounced AP amplitude alternans just before the onset of fibrillation. We used a simplified ionic cell model to derive a return map and a stability condition that elucidates a novel underlying mechanism for AP alternans and spiral breakup. We found that inactivation of the sodium current is key to developing amplitude alternans and is directly connected to conduction block and initiation of arrhythmias. Simulations in 2D where AP amplitude alternation led to turbulence confirm our hypothesis.