AVRT

• occurs in Wolff-Parkinson-White syndrome

• in this, there is a second conduction pathway along the atrio-ventricular brim

• the reentry involves using both the AV node and an accessory pathway as the retrograde limb

• ECG
  

  • patients with AVRT might not always be in arrhythmia

  • you see a widened QRS caused by preexcitation

  • normally, SA conducts to AV node. AV conducts quite slowly (120 ms)

  • accessory pathway, however, is much faster. by the time the AV node is done conducting, the accessory pathway has long since depolarized the ventricles

  • that gives you a delta wave on the ECG, a big, triangular wave, followed by atrial depolarization p wave. the upslope is the early excitation of the ventricle from accessory pathway

  • narrow complex QRS looking quite normal

  • often difficult to see atrial activity. in AVNRT, P wave is right after R’ wave; in AVRT, P wave is delayed a little bit after R’ wave

• rx

  • increase vagal tone with Valsalva, carotid sinus massage, IV adenosine to terminate AVRT

  • antiarrhythmic drugs to block conduction down accessory pathway (Class I, Class III) or may be used to slow AV node conduction (Class II, Class IV)

  • catheter ablation is treatment of choice for symptomatic patients

Category: Pathology Notes