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INTRODUCTION

Supraventricular tachyarrhythmias originate from or are dependent on conduction through the atrium or atrioventricular (AV) node to the ventricles. Most produce narrow QRS-complex tachycardia (QRS duration <120 ms) characteristic of ventricular activation over the Purkinje system. Conduction block in the left or right bundle branch or activation of the ventricles from an accessory pathway produces a wide QRS complex during supraventricular tachycardia that must be distinguished from ventricular tachycardia (Chap. 249). Mechanisms of supraventricular tachyarrhythmia can be divided into physiologic sinus tachycardia and pathologic tachycardia (Table 241-1). Pathologic tachycardia can be further sub-classified in terms of mechanism as reentrant arrhythmias dependendent on AV nodal conduction (e.g., AV reentry), large reentry circuits within the atrial tissue alone (e.g., atrial flutter) or focal atrial tachycardias that can be due to automaticity or small reentry circuits (see Figs. 243-3 and 245-1). The prognosis and treatment vary considerably depending on the mechanism and underlying heart disease.

TABLE 241-1Supraventricular Tachycardia

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