Abstract
The most common sustained cardiac arrhythmias in humans are atrial tachyarrhythmias, mainly atrial fibrillation. Areas of complex fractionated atrial electrograms and high dominant frequency have been proposed as critical regions for maintaining atrial fibrillation; however, there is a paucity of data on the relationship between the characteristics of electrograms and the propagation pattern underlying them. In this study, a realistic 3D computer model of the human atria has been developed to investigate this relationship. The model includes a realistic geometry with fiber orientation, anisotropic conductivity and electrophysiological heterogeneity. We simulated different tachyarrhythmic episodes applying both transient and continuous ectopic activity. Electrograms and their dominant frequency and organization index values were calculated over the entire atrial surface. Our simulations show electrograms with simple potentials, with little or no cycle length variations, narrow frequency peaks and high organization index values during stable and regular activity as the observed in atrial flutter, atrial tachycardia (except in areas of conduction block) and in areas closer to ectopic activity during focal atrial fibrillation. By contrast, cycle length variations and polymorphic electrograms with single, double and fragmented potentials were observed in areas of irregular and unstable activity during atrial fibrillation episodes. Our results also show: 1) electrograms with potentials without negative deflection related to spiral or curved wavefronts that pass over the recording point and move away, 2) potentials with a much greater proportion of positive deflection than negative in areas of wave collisions, 3) double potentials related with wave fragmentations or blocking lines and 4) fragmented electrograms associated with pivot points. Our model is the first human atrial model with realistic fiber orientation used to investigate the relationship between different atrial arrhythmic propagation patterns and the electrograms observed at more than 43000 points on the atrial surface.
Highlights
The most common sustained cardiac arrhythmias in humans are related to the atria
Atrial action potential propagation An atrial propagation pattern in sinus rhythm was simulated in the model by applying a periodic stimulus (10 beats) at a basic cycle length of 1000 ms in the anatomic location of the sinoatrial node (SAN)
The activation wave propagated to left atrium (LA) through the third interatrial connection, the right atrium (RA)-coronary sinus (CS)-LA pathway, at 87 ms and 98 ms, respectively, and the first LA inferior wall activation was observed at 117 ms and 132 ms for normal and remodeled atria, respectively
Summary
The most common sustained cardiac arrhythmias in humans are related to the atria. Different atrial arrhythmias, mainly atrial fibrillation (AF), often provoke disabling symptoms and severe complications such as heart failure and stroke [1]. There are several experimental observations regarding the important role of the anatomical structure and electrophysiological heterogeneity on atrial electrical activity both in physiological and pathological conditions [2,3,4]. It has been shown that atrial tachyarrhythmias produce a set of changes in atrial properties that lead to their perpetuation. These changes, denoted atrial remodeling, include alterations in the electrical cellular activity and in the anatomical structure. They have been described in several animal models [5] and in humans [6,7]. Changes in electrical activity cause a decrease in refractoriness subsequent to a significant action potential duration (APD) shortening [6,7,8], which may help the initiation and maintenance of multiple reentrant waves, as suggested by experimental studies [5,6]
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