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Updated: Mar 18, 2026

A New Single Chamber Implantable Defibrillator with Atrial Sensing: A Practical Demonstration of Sensing and Ease of Implantation
Published on: February 28, 2012
"2 for 1 Phenomenon" on Implantable Cardioverter Defibrillator Intracardiac Tracing
Eric McCLENDON1, Takeki Suzuki1, Tanyanan Tanawuttiwat1
1Department of Medicine, University of Mississippi Medical Center, Jackson, Mississippi.
Abstract:
"2 for 1 phenomenon" is simultaneous anterograde conduction over the fast and slow pathways of the atrioventricular (AV) nodal pathway, leading to a double ventricular response from each atrial beat. This phenomenon can initiate AV nodal reentrant tachycardia (AVNRT). The unique induction of AVNRT was observed in a patient with an implantable cardioverter defibrillator in our case. Minimal to no retrograde invasion of the slow pathway from the anterogradely conducted fast pathway depolarization is the most accepted explanation.
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