title: Cardiac dynamics: Alternans and arrhythmogenesis.
abstract: Pre-existing heterogeneities present in cardiac tissue are essential for maintaining the normal electrical and mechanical functions of the heart. Exacerbation of such heterogeneities or the emergence of dynamic factors can produce repolarization alternans, which are beat-to-beat alternations in the action potential time course. Traditionally, this was explained by restitution, but additional factors, such as cardiac memory, calcium handling dynamics, refractory period restitution, and mechano-electric feedback, are increasingly recognized as the underlying causes. The aim of this article is to review the mechanisms that generate cardiac repolarization alternans and convert spatially concordant alternans to the more arrhythmogenic spatially discordant alternans. This is followed by a discussion on how alternans generate arrhythmias in a number of clinical scenarios, and concluded by an outline of future therapeutic targets for anti-arrhythmic therapy.
authors.affiliation: School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, University of Hong Kong, Hong Kong.
authors.forename: Gary
authors.initials: G
authors.lastname: Tse
authors.affiliation: Faculty of Medicine, Imperial College London, SW7 2AZ London, UK.
authors.forename: Sheung Ting
authors.initials: ST
authors.lastname: Wong
authors.affiliation: Department of Physiology, McGill University, Canada.
authors.forename: Vivian
authors.initials: V
authors.lastname: Tse
authors.affiliation: School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, University of Hong Kong, Hong Kong.
authors.forename: Yee Ting
authors.initials: YT
authors.lastname: Lee
authors.affiliation: School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, University of Hong Kong, Hong Kong.
authors.forename: Hiu Yu
authors.initials: HY
authors.lastname: Lin
authors.affiliation: Faculty of Medicine, Imperial College London, SW7 2AZ London, UK.
authors.forename: Jie Ming
authors.initials: JM
authors.lastname: Yeo
keywords: Alternans; Cardiac arrhythmia; Dynamics; Re-entry; Restitution