Characterization and Comparison of Na^+, K^+ and Ca^2+ Currents Between Myocytes from Human Atrial Right Appendage and Atrial Septum

Abstract

Atrial pacing to reduce paroxysmal atrial fibrillation recurrences is performed in right atrial appendage (RAA) traditionally. However, recent studies indicate that atrial septal (AS) pacing produces better outcomes than the RAA pacing. The underlying mechanisms for this difference remained unclear. One possible explanation for the superiority of AS pacing over RAA pacing is that the two different regions have distinct electrophysiological properties. The study was to explore whether there indeed exist regional differences of electrical activities between RAA and AS, using whole-cell patch clamp techniques. The results showed that RAA cells had longer action potential duration, more negative resting potential and greater amplitude of action potential, whereas AS cells had more rapid depolarizing velocity. The sodium current was significantly smaller in RAA cells, whereas the calcium current was markedly smaller in AS cells. The transient outward K⁺ current was similar in both regions. The ultrarapid delayed rectifier K⁺ current was greater in RAA than that in AS cells. The inward rectifier K⁺ current was similar at potentials more negative to -60 mV in both regions. The results indicate that RAA and AS of patients with rheumatic heart disease possess distinct electrophysiological properties. These differences provided a rational explanation for the different efficacies in treating atrial fibrillation by atrial pacing in RAA and AS regions.

Recent progress in multi-scale models of the human atria

“…In both Colman et al [15] and Kruger et al [22] an extensive family of regional cell models has been developed for sinus rhythm and cAFeR conditions. The large variation in AP morphology and duration observed experimentally [3,27] is replicated in both models (Fig. 1f), and both demonstrate that cAFeR reduces but does not eliminate this heterogeneity.…”

“…The atria are characterised by a large degree of variation in electrical properties between different anatomical regions [3,27], and this variation has been demonstrated to play an important role in atrial repolarisation and susceptibility to wave-breaks (see 'Mechanisms of atrial fibrillation' section and [15,28,29]). In both Colman et al [15] and Kruger et al [22] an extensive family of regional cell models has been developed for sinus rhythm and cAFeR conditions.…”

“…All of these data can be incorporated into 3D models of the whole atria to simulate atrial electrical activity in normal and abnormal conditions (e) and incorporated into torso models to simulate body-surface potential (BSP) and electro-cardiograms (ECGs) (f). Images in (a) adapted from [19,27] and (c) adapted from [55]. Data in (b) is from [4,45,47] and (e) is from [15].…”

Arrhythmogenic potential of oxidative stress in atrial myocytes

“…The present study aims to study the effects of oxidative stress on the electrophysiological properties in atrial myocytes and thereby reveal the contribution of oxidative stress to AF. The methods to perform electrophysiological investigation using the whole-cell patch clamp were as described previously [9].We firstly investigated the influences of oxidant stress on the action potential in atrial myocytes of guinea pigs. After guinea pig atrial myocytes were exposed to 1 mmol/L H 2 O 2 , action potential (AP) was recorded in a whole-cell current-clamp model with 20 s interval.…”

“…The present study aims to study the effects of oxidative stress on the electrophysiological properties in atrial myocytes and thereby reveal the contribution of oxidative stress to AF. The methods to perform electrophysiological investigation using the whole-cell patch clamp were as described previously [9].…”