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AVNRT, but has a variable success rate in abolishing tachycardia episodes, ranging from 13 - 82%, and <_20% of patients may discontinue therapy.323 In view of the excellent success rate and minimal risk of catheter ablation in symptomatic cases, the value of longterm antiarrhythmic drug therapy seems very limited.

11.2.2 Non-re-entrant junctional tachycardias Junctional ectopic tachycardia (JET), or focal junctional tachycardia, is an uncommon arrhythmia that arises from abnormal automaticity at the AVN or proximal His bundle. Focal junctional tachycardia in children may be seen as a congenital arrhythmia or, more often, early after infant open-heart surgery.366,367 Congenital junctional tachycardia carries considerable morbidity and mortality.368 Junctional tachycardia can also be seen in adult patients with a structurally normal heart,369,370 and has in the past been associated with non-fibrinolysed acute MI.371 The usual ECG finding in JET is a narrow QRS tachycardia with a short RP interval or AV dissociation. Occasionally, the tachycardia might be irregular and resemble AF. Propranolol (i.v.) with or without procainamide,370 verapamil, or procainamide,372 or flecainide,373 may be used for acute therapy, but data are scarce. Amiodarone (i.v.) is the drug of choice for post-operative JET as well as for preventing early JET in children after open-heart surgery.374,375 In children with congenital junctional tachycardia, amiodarone alone, or with propafenone or ivabradine, appears effective.368,376379 For chronic therapy, propranolol370 or, in the absence of ischaemic or structural heart disease, flecainide380 and propafenone,381 may be tried. Selective catheter ablation at the site of the earliest retrograde atrial activation is feasible, but carries a lower success rate and higher AV block risk compared with AVNRT (5 - 10%).369,382

Cryoablation is safer.375,383 Non-paroxysmal junctional tachycardia was frequently diagnosed in the past as a junctional rhythm of gradual onset and termination, with a rate between 70130 b.p.m., and was considered a typical example of digitalis-induced DADs and triggered activity in the AVN.3 The RP interval during tachycardia is variable. Myocardial ischaemia, hypokalaemia, chronic obstructive pulmonary disease, and myocarditis are also associated conditions. Non-re-entrant AV nodal tachycardia caused by simultaneous multiple nodal pathway conduction (often called double-fire pathology or dual AV nodal tachycardia) is an uncommon mechanism of AV nodal tachycardia,384,385 and has been associated with repetitive retrograde concealment or ‘linking’ phenomena.386388 These are expressed in the form of ventricular pauses with consistent AV relationship after the pause, and can often be misdiagnosed as AF.389 These extremely rare tachycardias may cause TCM and respond to slow-pathway ablation.

11.3 Atrioventricular arrhythmias

AVRTs use an anatomically defined re-entrant circuit that consists of two limbs: first, the AVNHPS, and second, an AP also called the bypass tract. The two limbs are characterized by differences in refractoriness and conduction times, with critically timed premature atrial or ventricular beats initiating re-entrant tachycardia. On rare occasions, the circuit consists of two APs.

11.3.1 Accessory pathways APs are single or multiple strands of myocardial cells that bypass the physiological conduction system, and directly connect atrial and ventricular myocardium.390 These AV connections are due to incomplete embryological development of the AV annuli, without complete separation of the atria and ventricles. While there are different types of APs, the most common are those that connect the atrium and the ventricle along the mitral or tricuspid annulus. Approximately 60% are located along the mitral valve and are referred to as left free wall APs, 25% insert along the septal aspect of the mitral or tricuspid annulus, and 15% insert along the right free wall.391393 Because ventricular muscle is lacking in the proximity of the anterior leaflet of the mitral valve, left-sided APs are usually limited to the region of the mitral annulus at the attachment of the mural (posterior) leaflet. APs located in the superoparaseptal area in close proximity to the His bundle and AVN may also occur.394 APs present characteristic electrophysiological features that differ from AV nodal conduction properties. They typically exhibit fast conduction (with the exception of atypical pathways-see section 11.3.9), dependent on a sodium current similar to that of myocardial cells. Moreover, although a majority of APs conduct both antegradely and retrogradely, some propagate impulses in only one direction. Those that conduct in the antegrade direction only are uncommon (<_10%),

©ESC 2019

Catheter ablation

(I B)

Diltiazem or verapamil

or beta-blocker or diltiazem plus beta-blocker

(IIa B)

No

No

Yes

Yes

If ineffective

Symptomatic and

recurrent

Drug therapy

desirable

AVNRT

Figure 15 Chronic therapy of atrioventricular nodal re-entrant tachycardia. AVNRT = atrioventricular nodal re-entrant tachycardia. Downloaded from academic.oup.com/eurheartj/article/41/5/655/5556821 by guest on 07 October 2026