AVNRT + AVRT

Atul Jaidka

Overview

  1. SVT
  2. AVNRT
  3. AVRT
  4. ECG Practise

References

  1. Uptodate
  2. Circulation AVNRT Review
  3. 2015 ACC/AHA/HRS Guideline for the Management of Adult Patients With Supraventricular Tachycardia
  4. 2019 ESC Guidelines for the management of patients with supraventricular tachycardia

SVT

CMAJ

SVT

AHA

SVT

UTD

SVT

  • AVNRT 60%
  • Accessory Pathway 30%
  • AT 10%

UTD

AVNRT

AVNRT

  • Narrow Complex Tachycardia
  • QRS<120 unless aberrancy (usually RBBB)
  • Precise anatomy and pathways unknown

AVNRT - Clinical

  • Average age of onset 32+/- 18
  • Symptoms: 

    • Palpitations – 98 percent

    • Dizziness – 78 percent

    • Dyspnea – 47 percent

    • Chest pain – 38 perceny

    • Fatigue – 19 percent

    • Syncope – 16 percent

  • Shirt-flapping, neck pounding (? from canon A waves)
  • Poluria (left atrial stretch and high atrial natriuetic peptides)

Anatomy

https://www.google.com/url?sa=i&url=https%3A%2F%2Fwww.pinterest.com%2Fpin%2F341569952981550993%2F&psig=AOvVaw0yDZK_osjezUQ7RZxw1Qgr&ust=1605544422492000&source=images&cd=vfe&ved=0CAIQjRxqFwoTCND3q97-hO0CFQAAAAAdAAAAABAW

UTD

Sinus

PAC

Slow-Fast Circuit

UTD

Note

  • This is a model
  • It explains: PAC can start the arrhythmia and premature beat can end it
  • Not perfect as not all patients with AVNRT have dual AV node physiology on EP studies and no all patients with dual AV node physiology have AVNRT

AVNRT - Slow Fast

UTD

Circulation

ECG Characteristics

  • Ventricular rate generally between 120-22
  • Abrupt initiation with PAC with PR prolongation (slow pathway conduction)
  • Typical AVNRT the p wave is either just before, inside, or just after the QRS
    • When after QRS may form: pseudo-R' in V1 and a pseudo-S wave in the inferior leads.
  • When p waves are visible, inverted in inferior leads due to retrograde activation (bottom to top)
  • ST depressions can occur in 30-50% patients (not ischemia)
  • T wave inversions in ant/inf leads after termination (thought to be due to rapid rates)

UTD

https://litfl.com/avnrt-for-two/

https://litfl.com/avnrt-for-two/

Atypical AVNRT

  • 6% of all cases
  • Key difference is retrograde conduction using slow pathway which gives a long RP (HA interval >70ms)
  • Anterograde conduction with either a fast pathway (may be different than usual fast pathway) or a slow pathway

Atypical AVNRT

AH = anterograde time, HA = retrograde time

Fast-Slow

Often initiated by a PVC

UTD

Circulation

Management

Acute

AHA

Ongoing

AHA

ESC

Vagal Maneuvers: ESC: recommend modified valsalva

AHA: regular valsalva, carotid massage, ice cold wet towel to face

WPW

Definitions

  • AVRT: reentry circuit using AV-HIS and AP
  • Accessory Pathway (AP): single or multiple strands of myocardial cells that bypass the physiological conduction system, and directly connect atria and ventricle
  • Pre-excitation: (i) a short PR interval (≤120 ms); (ii) slurred upstroke (or downstroke) of the QRS complex (‘delta wave’); and (iii) a wide QRS complex (>120 ms)
  • WPW Pattern: pre-excitation on ECG
    • 0.13-0.25% of general population
  • WPW Syndrome: pre-excitation on ECG and clinical arrhythmia
    • Large cohort, 0.25% WPW pattern, 1.8% WPW syndrome

WPW

  • Symptoms: Palpitations, lightheadedness and/or dizziness, syncope or presyncope, chest pain, sudden cardiac arrest
  • Arrhythmias:
    • Tachycardias requiring an accessory pathway
      • Orthodromic and Antidromic AVRT
    • Tachycardias not requiring an accessory pathway
      • AVNRT
      • Atrial fibrillation
      • Atrial Flutter
      • VT
      • Vfib and SCD

Accessory Pathway

  • 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
  • ∼15% insert along the right free wall
  • Most AP conduct anterograde and retrograde and use fast conduction
  • When AP conducts anterograde, pre-excitation is noted on ECG and referred to as manifest

UTD

Accessory Pathway

  • Localization is possible with alogorithms (won't be discussed today)

AVRT

  • reentry circuit that has 2 limbs:
    • AVN-HIS
    • Accessory Pathway

UTD

AVRT

ECGwaves.com

Narrow

Wide

Orthodromic AVRT

  • >90% of AVRT
  • 150-250BPM
  • Inverted P waves with an RP interval that is usually less than one-half the tachycardia RR interval
  • Narrow QRS unless functional BBB
  • ST-segment depression
  • Initiated by PAC or PVC

Orthodromic AVRT

UTD

CardioGuide

Orthodromic AVRT

  • Ventricular rate ranging from 150 to 250 (or greater) beats per minute and usually regular
  • Wide QRS complexes which are fully preexcited
  • Inverted P waves with an RP interval that is usually more than one-half the tachycardia RR interval and a short PR interval
  • Constant RP interval regardless of the tachycardia cycle length
  • Initiated with PAC or PVC

Orthodromic AVRT

UTD

LIFTL

Other Arrhythmias 

  • Atrial fibrillation: 10-30% of WPW syndrome
    • ECG: irregularly irregular rhythm with QRS morphology changes from beat to beat, which may be associated with rapid AV transmission
  • Atrial Flutter: may conduct 1:1 through accessory pathway and look like VT, can degenerate to VF
  • VT: uncommon
  • VF: uncommon as primary arrhythmias, usually SVT that degenerated

LIFTL

Management

Acute

AHA

Acute

ESC

Ongoing

AHA

ESC

Asymptomatic Patient

ESC

High-risk features at electrophysiology study are shortest preexcited RR interval during atrial fibrillation <_250 ms, accessory pathway effective refractory period <_250 ms, multiple accessory pathways, and inducible atrioventricular re-entrant tachycardia. 

Low-risk features at non-invasive risk stratification are induced or intermittent loss of pre-excitation on exercise or drug testing, resting electrocardiogram, and ambulatory electrocardiogram monitoring

UTD

AHA

Driving

AVNRT/AVRT

By Atul Jaidka

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AVNRT/AVRT

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