A study on determinants of the inducibility and maintenance of atrial fibrillation

Cho, Jeong Gwan; Park, Hyung Wook; Bae, Youl; Yoon, Nam Sik; Koh, Jeom Suk; Lim, Ji Hyun; Yang, Bora; Kim, Han Gyun; Hong, Young Joon; Kim, Joo Han; Kim, Weon; Ahn, Young Keun; Jeong, Myung Ho; Park, Jong Chun; Kang, Jung Chaee

Abstract

BACKGROUND: Atrial fibrillation (AF) is thought to beget AF by shortening atrial refractoriness and reversal of rate adaptation of atrial refractoriness. This phenomenon of electrophysiologic remodeling of the atria during AF has been reported to play a major role in inducibility and stability of AF.
METHODS
Thirty-one patients with induced AF lasting >1 second during electrophysiologic study for documented or suspected supraventricular or ventricular tachycardia were included in this study. All the patients had no structural heart disease and history of AF. High right atrium (HRA) burst pacing or extra-stimulation was applied to induce AF. Eleven patients with AF sustained >or=3 min was grouped into Group I and 20 patients with AF <3 min into Group II. P wave duration and amplitude, left atrial (LA) size, atrial refractory period (ARP), intraatrial conduction time (IACT) from HRA electrode catheter to His bundle electrode catheter and characteristics of atrial activities during induced AF were compared between 2 groups.
RESULTS
There was no difference in the distribution of underlying cardiac arrhythmias. P wave durations and amplitudes and echocardiographic LA sizes were similar between 2 groups. ARPs and IACTs in group I and II were similar (198.0 +/- 23.9 ms vs. 200.8 +/- 23.0 ms; 38.7 +/- 8.5 ms vs. 38.6 +/- 9.5 ms, respectively). During AF, mean interval of atrial activities in group I was significantly shorter than group II (156.6 +/- 24.2 ms vs. 187.6 +/- 28.0 ms, p<0.01). The degree of irregularity of atrial activities during AF was significantly higher in group I than group II (16.9 +/- 8.7 vs. 9.8 +/- 5.0, p<0.05). The duration of the atrial activities was wider in group I than group II (81.4 +/- 17.5 ms vs. 53.9 +/- 12.4 ms, p<0.001) and the amplitude was lower in group I than group II (56.1 +/- 36.0% vs. 109.0 +/- 51.8%, p<0.05), and the degree of fractionation was greater in group I than group II (4.8 +/- 1.1 vs. 3.2 +/- 0.5, p<0.05).
CONCLUSION
These results suggest that shortening of atrial refractoriness and lengthening of local conduction time at the time of or shortly after induction of AF may play a major role in the induction and stabilization of AF.