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. 2020 May 20.
doi: 10.1161/CIRCEP.119.008179. Online ahead of print.

Triggered Ca2+ Waves Induce Depolarization of Maximum Diastolic Potential and Action Potential Prolongation in Dog Atrial Myocytes

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Triggered Ca2+ Waves Induce Depolarization of Maximum Diastolic Potential and Action Potential Prolongation in Dog Atrial Myocytes

Georg Gussak et al. Circ Arrhythm Electrophysiol. .

Abstract

Background - We have identified a novel form of abnormal Ca2+ wave activity in normal and failing dog atrial myocytes which occurs during the action potential (AP) and is absent during diastole. The goal of this study was to determine if triggered Ca2+ waves affect cellular electrophysiological properties. Methods - Simultaneous recordings of intracellular Ca2+ and APs allowed measurements of maximum diastolic potential (MDP) and AP duration (APD) during TCWs in isolated dog atrial myocytes. Computer simulations then explored electrophysiological behavior arising from TCWs at the tissue scale. Results - At 3.3-5hz, TCWs occurred during the AP and often outlasted several AP cycles. MDP was reduced and APD was significantly prolonged during TCWs. All electrophysiological responses to TCWs were abolished by SEA0400 and ORM10103, indicating that Na-Ca exchange current caused depolarization. The time constant of recovery from inactivation of Ca2+ current was 40-70ms in atrial myocytes (depending on holding potential) so this current could be responsible for AP activation during depolarization induced by TCWs. Modeling studies demonstrated that the characteristic properties of TCWs are potentially arrhythmogenic by promoting both conduction block and reentry arising from the depolarization induced by TCWs. Conclusions - Triggered Ca2+ waves activate inward NCX and dramatically reduce atrial MDP and prolong APD, establishing the substrate for reentry which could contribute to the initiation and/or maintenance of atrial arrhythmias.

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