Dynamic changes in intracardiac resistance as a predictive marker during internal cardioversion of atrial fibrillation

Intracardiac resistance (ICR) is an important determinant of treatment success during internal cardioversion of atrial fibrillation (AF). However, there is limited data on dynamic changes in ICR as a predictor of cardioversion outcome. In this retrospective study, thirty patients with persistent AF were randomised to treatment with a biphasic or monophasic energy step-up cardioversion protocol (50V-to-300V in 50V steps). ICR was computed for each patient and a student t-test used to investigate the significance of dynamic changes in ICR between successive shocks delivered. For both biphasic and monophasic waveforms, all patients who cardioverted exhibited a significant reduction in ICR between the first and third shock (p<;0.01 and p<;0.003, respectively). Yet, critically, a significant reduction in ICR was absent for all patients who failed to cardiovert (p>0.05 for both waveforms). A statistically significant decrease in ICR during the first three shocks was identified as a predictive marker for successful cardioversion outcome.