AVRT is a supraventricular tachycardia that utilizes an accessory pathway between the atria and ventricles resulting in a circus movement
It is frequently, but not exclusively, associated with preexcitation syndrome (ie, the Wolff-Parkinson-White syndrome)
The circuit involved in this reentrant arrhythmia includes the accessory bypass tract, AV node, and His Purkinje system, as well as the atria and ventricles
There is always 1:1 conduction of the impulse between the atria and ventricles since both structures, along with the AV node and accessory pathway, are a necessary part of the circuit
AVRT is often triggered by premature atrial beats or premature ventricular beats – retrograde activation of atria
Classification and ECG findings
Based on direction of reentry circuit AVRT is divided into 2 groups:
Orthodromic AVRT
>90% of AVRT
re-entrant impulse goes from the atria to the ventricles through the AV node (normal ventricular activation) and then retrogradely activates atria through accessory pathway
ECG:
narrow complex tachycardia
ventricular rate 150-250 bpm
inverted P wave following a QRS complex - retrograde activation of the atrium
short RP interval that is usually less than half of RR interval (< ½ RR)
Antidromic AVRT
<10% of AVRT
Ventricles are activated through an accessory pathway - atria are retrogradely activated over the AV node (or over another accessory pathway - some patients might have multiple accessory pathways)
ECG:
wide QRS complex tachycardia
ventricular rate 150-250 bpm
Inverted P waves are often hidden in ST-T segment and therefore the RP interval is usually difficult to assess
Picture 1 Differentiation between orthodromic and antidromic AVRT
Picture 2 Differential diagnosis of supraventricular tachycardia based on the relationship of P waves and QRS complexes
Carotid sinus massage - after auscultation of both carotid arteries (exclude significant stenosis) - pressure is applied to one carotid sinus for 5 to 10 seconds. Steady pressure is recommended because it may be more reproducible. If the expected response is not obtained, the procedure is repeated on the other side after a one- to two-minute delay.
Valsalva manoeuvres – patient is instructed to exhale forcefully against a closed glottis (against closed mouth and compressed nose) for 10 – 15s and then release.
Modified Valsalva manoeuvre – patient does classical Valsalva manoeuvre followed by 15 seconds of passive leg raise at 45 degree angle – this may be more successful in restoring sinus rhythm.
If vagal manoeuvres are ineffective:
For orthodromic AVRT:
Adenosine
use with caution! – potential induction of atrial fibrillation with fast ventricular conduction or ventricular fibrillation
electrical cardioversion should always be available when administering adenosine
6 mg i.v. as a rapid bolus with saline flush
second dose – 12 mg i.v., safe within 1 min of the last dose
maximum dose = 18 mg
If Adenosine is ineffective > pharmacological therapy directed at AV node:
Pharmacological therapy directed at fast-conducting AP (accessory pathway):
i.v. ibutilide or procainamide
i.v. propafenone or flecainide
Synchronized cardioversion
Chronic therapy
The treatment of choice for patients with symptomatic and recurrent AVRT is catheter ablation of accessory pathway
Propafenone or flecainide may be considered in patients with AVRT and without ischaemic or structural heart disease, if ablation is not desirable or feasible
Picture 3 Treatment of AVRT as per ESC guidelines
References
CAMM, A. J., LÜSCHER, T. F., & SERRUYS, P. W. (2009). The ESC textbook of cardiovascular medicine. Oxford, Oxford University Press
Brugada J, Katritsis DG, Arbelo E, Arribas F, Bax JJ, Blomström-Lundqvist C, Calkins H, Corrado D, Deftereos SG, Diller GP, Gomez-Doblas JJ, Gorenek B, Grace A, Ho SY, Kaski JC, Kuck KH, Lambiase PD, Sacher F, Sarquella-Brugada G, Suwalski P, Zaza A; ESC Scientific Document Group. 2019 ESC Guidelines for the management of patients with supraventricular tachycardiaThe Task Force for the management of patients with supraventricular tachycardia of the European Society of Cardiology (ESC). Eur Heart J. 2020 Feb 1;41(5):655-720. doi: 10.1093/eurheartj/ehz467. PMID: 31504425.