EP Lab Challenge

Arrhythmia Grand Rounds, April 2015, Volume 1, Issue 1: 35
DOI: 10.12945/j.agr.2015.00006-14

Worth the delay

Yash Y. Lokhandwala, MD

Arrhythmia Associates, Mumbai, India


Presence of manifest pre-excitation suggestive of a right-sided accessory pathway (AP) is not proof that a patient’s symptoms are caused by it. Before ablation is undertaken, tachycardia should be induced and participation of the AP in mediating the tachycardia should be demonstrated.

Right-sided pathways may have Kent-like conduction properties or Mahaim-like conduction properties. A Mahiam-like, decrementally conducting AP during a pre-excited tachycardia can be suspected by measuring the atrioventricular (A–V) interval at the His bundle recording during tachycardia. Proof of AP participation in the tachycardia circuit can be obtained by advancing ventricular activation after a critically timed atrial premature beat (APB) delivered during AV node or His bundle refractoriness. These APBs can be delivered in the right atrial lateral wall and may result in one of 4 types of responses in patients with a decrementally conducting AP. Furthermore, reset of the tachycardia my either result in advancement or delay of ventricular activation. This case illustrates and discusses these principles.


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