In 1930, Louis Wolff, Sir John Parkinson, and Paul Dudley White published a seminal article describing 11 patients who suffered from attacks of tachycardia associated with a sinus rhythm electrocardiographic (ECG) pattern of bundle branch block with a short PR interval . This was subsequently termed the Wolff-Parkinson-White (WPW) syndrome, although earlier isolated case reports describing similar patients had been published. In 1943, the ECG features of preexcitation were correlated with anatomic evidence for the existence of anomalous bundles of conducting tissue that bypassed all or part of the normal atrioventricular (AV) conduction system (figure 1).
Atrioventricular reentrant (or reciprocating) tachycardia (AVRT) is a reentrant tachycardia with an anatomically defined circuit that consists of two distinct pathways, the normal AV conduction system and an AV accessory pathway, linked by common proximal (the atria) and distal (the ventricles) tissues. While other arrhythmias can utilize the accessory pathway for conduction from the anatomic site of tachycardia origin to other regions of the heart (eg, atrial fibrillation and atrial flutter) (figure 2), AVRT is a specific reentrant tachycardia in which the accessory pathway is necessary for initiation and maintenance of the tachycardia .
The different types of AVRT, along with their ECG findings, will be discussed here. The approach to treatment of arrhythmias associated with an accessory pathway is presented in detail separately. (See "Treatment of symptomatic arrhythmias associated with the Wolff-Parkinson-White syndrome".)
NORMAL AV CONDUCTION VERSUS ACCESSORY AV PATHWAY CONDUCTION
Normal atrioventricular (AV) conduction occurs through the AV node. However, in the presence of an accessory pathway, conduction from the atria to the ventricles may occur in a variety of ways (exclusively via the AV node, exclusively via the accessory pathway, or a combination of both). Normal and accessory AV conduction are discussed in detail elsewhere. (See "Epidemiology, clinical manifestations, and diagnosis of the Wolff-Parkinson-White syndrome", section on 'Normal AV conduction versus accessory AV pathway conduction'.)
TACHYCARDIAS REQUIRING AN AV ACCESSORY PATHWAY FOR INITIATION AND MAINTENANCE
Atrioventricular reentrant (or reciprocating) tachycardia (AVRT) is a reentrant tachycardia with an anatomically defined circuit that consists of two distinct pathways, the normal AV conduction system and an AV accessory pathway, linked by common proximal (the atria) and distal (the ventricles) tissues. If sufficient differences in conduction time and refractoriness exist between the normal conduction system and the accessory pathway, a properly timed premature impulse of atrial, junctional, or ventricular origin can initiate reentry. (See "Reentry and the development of cardiac arrhythmias".)