4 Insights into the mechanisms of triggered activity during long qt conditions in the intact heart using optical mapping

Introduction: Early afterdepolarisations (EADs) are cellular events defined as depolarisation during the early repolarisation phase of the action potential (AP).  EAD-triggered APs are thought to be responsible for the induction of Torsades de Pointes (TdP) polymorphic ventricular tachycardia in the long QT syndrome (LQTS). This cellular mechanism cannot be directly extrapolated to the intact heart, where electrotonic coupling will oppose any local depolari sation. Indeed, computational modelling has estimated that synchronisation of EADs across thousands of cells is required for an EAD-triggered AP to propagate in the intact heart.   An alternative mechanism is that where marked heterogeneity in repolarisation exists, current can flow between depola rised and repolarised regions thereby producing a triggered AP without the requirement for a cellular EAD event in the depolarised region. The aim of this study was to examine these two possible mechanisms using optical mapping of Vm and Ca2+ in the intact rabbit heart under LQT conditions.

Source: Europace - October 5, 2017 Category: Cardiology Source Type: research