Atrial Ectopic Tachycardias
Disorders of impulse formation account for approximately 10 % of supraventricular tachycardia (SVT) in infants and children. These include automatic atrial tachycardia (AAT), also known as atrial ectopic tachycardia (AET), originating from a single focus in the atrium, multifocal atrial tachycardia (MAT, or chaotic atrial tachycardia) thought to arise from multiple foci within the atria (Chap. 12), congenital junctional ectopic tachycardia (JET, Chap. 11)), and accelerated junctional rhythm (Chap. 13), both originating from tissue in the region of the atrioventricular (AV) node. They are characterized electrophysiologically by a point origin, in contrast to tachycardias supported by macroreentrant circuits where larger segments of tissue with abnormal conduction perpetuate the arrhythmia.
The precise cellular mechanism of disorders of impulse formation can only be inferred in patients with atrial ectopic tachycardia. Both abnormal transmembrane potassium (pacemaker) and calcium (triggered activity) currents have been proposed as the mechanism of abnormal automaticity, based on both cellular laboratory observations and indirect clinical evidence.
KeywordsAccelerated junctional rhythm Atrial ectopic tachycardia Automatic atrial tachycardia Chaotic atrial tachycardia Congenital junctional ectopic tachycardia Multifocal atrial tachycardia Supraventricular tachycardia
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