Atrial tachycardias

Abstract

Atrial tachycardia is a focal or macro re-entry supraventricular arrhythmia which does not directly involve the AV node. Overall it accounts for approximately 7% of all SVT's (Wellens HJ, Circulation. 90(3): 1576-1577, 1994). Focal atrial tachycardia occurs as a result of either micro re-entry, increased automaticity or triggered activity while macro re-entry occurs over a region of tissue surrounding a region of conduction block. Focal atrial tachycardia due to increased automaticity can usually be initiated with isoprenaline while decremental atrial pacing tends to initiate and terminate micro and macro re-entry. Although atrial tachycardia's may occur anywhere within the right atrium or left atrium there are more common locations and in particular where anisotropic conduction occurs in which there is rapid linear conduction and slowed transverse conduction. The most common locations are the crista terminalis, coronary sinus os, the pulmonary veins and antral regions, the tricuspid and mitral annuli, the right and left atrial appendages and the interatrial septum. The location is to an extent dependent on the patient's age, history of structural heart disease, prior ablations or surgery and the presence of other arrhythmias.