| Introduction:The diagnosis of Atrial fibrillation was based on the inducibility and maintenance. While inducibility of atrial fibrillation (AF) is often utilized as an endpoint for RF ablation of AF, little is known regarding inducibility among normals. We therefore evaluated the inducibility of AF with rapid atrial pacing (RAP) in patients without a clinical history of AF, following catheter ablation of supraventricular tachycardia (SVT).Methods:We prospectively evaluated86patients without a history of AF who were referred for catheter ablation of SVT. After routine electrophysiological study and successful ablation of the SVT, two different RAP protocols for induction of AF were tested. First, AF induction was attempted by5-second bursts of atrial pacing from the coronary sinus ostium (CSO) at three different cycle lengths (CL). Next, continuous incremental stimulus(CIS) was performed from the CSO starting at CL250ms to the loss of1:1atrial capture. This protocol was repeated three times for each subject.Results:Three of subjects (3.5%) enrolled had inducible AF with the first pacing protocol. However, with the second protocol, AF was inducible in22patients (25.6%), including sustained AF in16patients (18.6%). There were significant differences in the inducibility of AF between the two atrial pacing protocols. Additionally, with the second pacing protocol, patients with loss of1:1atrial capture at CL<180ms were more easily inducible for AF (21/63vs1/23, P=0.006).Conclusion:Using a specific, atrial decremental pacing protocol,26%of patients without a history of AF had inducible AF, while18.6%lasting>5minutes. These findings suggest that the essence of AF may not be the inducibility but the maintenance. Background:There are great difficulties with the current therapies for persistent atrial fibrillation (PeAF), of which the maintaining mechanism is still unknown. The purpose of this study was to characterize the basic spatial and temporal distribution of atrial activities of PeAF by isochronal spectral analysis, and to identify the crucial substrate maintaining PeAF.Methods:The patients with PeAF referred for the first catheter ablation using a noncontact mapping in our hospital were enrolled. Left atrial activations of PeAF prior to the radiofrequency energy delivering were recorded in the noncontact mapping system. Digital data with geometry and electrograms information at2048locations were acquired and processed into a Custom-written Matlab system for spectral analysis. Regions with high-frequency activities were identified for each case. The dynamic electrophysiological variations and location of effective targets were routine recorded and evaluated. Comparisons were made between the locations of the effective targets and the high-frequency activation regions.Results:Forty-eight patients with PeAF referred for the first catheter ablation using a noncontact mapping were enrolled (male40cases, mean age53.35±10.24years old).The average sustained duration of PeAF was17.79±24.32months. Left atrium enlargement were documented in31patients, while12of which demonstrated bi-atrial enlargement. The average left atrial diameter measured by echocardiography was42.33±5.78mm. The8034.65±996.85ms atrial activation data prior to the ablation were analyzed. Local left atrial activation frequencies of PeAF varied from6.10Hz to11.80Hz. A total of203regions were detected as high-frequency activation regions in48patients (4.23±1.15regions/patient):91.67%(44patients) showed high-frequency activation in left atrial roof,75.00%(36patients) in the ridge between left atrial appendage and left superior pulmonary vein and68.75%(33patients) in the inter-atrial septum. Less high frequency activation located around the pulmonary veins and posterior wall. There were145effective episodes occurred during linear ablation in the48patients (140in left atrium,5in right atrium).77.14%of the effective targets were located within the high frequency activation regions (95%Cl:34.22%-82.80%):The accordance between the effective target and high-frequency activation region was97.30%in the roof,93.10%in the ridge and75.00%in the septum. Nineteen patients(39.58%) with PeAF were converted to sinus rhythm by stepwise linear ablation while another22patients were converted to sinus rhythm after concomitant ibutilide treatment. After an average of18.90±6.43months follow-up,37patients(77.08%) were sustained in sinus rhythm without antiarrhythmics, while9(18.75%) of which experienced a redo successful ablation for refractory left atrial flutter.Conclusions:The high-frequency activation of persistent atrial fibrillation were located in the roof, ridge and septum.77.14%of the effective targets of the stepwise linear ablation were accordance with the high-frequency activation regions. Isochronal spectral analysis would be helpful in identification of the critical substrate of persistent atrial fibrillation and in the option of appropriate ablation strategy. According to the results, left atrial linear ablation, especially the roof line, was essential in the control of persistent atrial fibrillation.
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