Atrial fibrillation induction and determination of atrial vulnerable period using very low energy synchronized biatrial shock in normal subjects and in patients with atrial fibrillation

The atrial vulnerable periods (AVP)for shock induction of atrial fibrillati on (AF) in humans have not been clearly defined. Furthermore, the safety an d efficacy of using low energy biatrial shock delivered transvenously for A F induction are unknown. We tested the safety and efficacy of using very lo w energy biatrial shocks, delivered between the right atrium and the corona ry sinus for AF induction and used this technique to characterize the AVP i n nine controls and nine patients with AF. Thirty-volt and 60-V 3/3-ms biph asic shocks were delivered, starting from 50 ms before the atrial effective refractory period with 20-ms increments until the end of the QRS interval to determine the AVP front, AVP end, and the AVP duration. Successful AF in duction could be achieved in eight (89%) of the nine controls and in nine ( 100%) of the nine patients with AF without any complication. In patients wi th AF, the AVP front started significantly earlier within the QRS complex, and the AVP duration and the AVP duration/QRS percent ratios were also sign ificantly greater as compared to controls. Furthermore, a higher induction shock energy in patients with AF was associated with an increase in AF indu cibility and significantly increased the A VP duration and A VP duration/QR S percent ratio as compared to the controls. This study demonstrated the sa fe and efficacy of delivering a very low energy biatrial shock during the A VP within the R wave for AF induction. The characteristics of AVP in patien ts with AF were significantly different from normal subjects.