Last reviewed 01/2018

The refractory period of the atrioventricular node normally prevents a supraventricular focus from driving the ventricles at greater than about 150 bpm. However in the presence of an alternate AV conduction pathway with a short refractory period, the ventricular response may exceed 200 bpm:

  • patients with Wolf-Parkinson-White syndrome and Lown-Ganong-Levine syndrome have alternate atrio- ventricular pathways which result in aberrant conduction of the myocardial depolarisation

  • re-entry tachycardias result from anterograde conduction through the AVN and retrograde conduction up the aberrant pathway

  • the process may be initiated by an ectopic beat