Impact of Atrial Fibrillation Termination on Clinical Outcome after Ablation in Relation to the Duration of Persistent Atrial Fibrillation

Background: Whether procedural termination of persistent atrial fibrillation (AF) is necessary for optimal clinical efficacy still remains controversial. We sought to characterize the patients with persistent AF in whom procedural AF termination impacted an improved clinical outcome after ablation. Methods: We retrospectively assessed 132 patients (61.0 ± 9.3 years, 114 males) undergoing catheter ablation of persistent AF (duration 3 years, median). A stepwise ablation approach including pulmonary vein isolation and atrial substrate ablation targeting complex fractionated and high‐frequency electrograms was performed with desired endpoint of AF termination. Results: Overall, 90 patients (68%) were free from recurrent arrhythmias at 20 ± 11 months of follow‐up after one or two procedures. The left atrial diameter and continuous AF duration according to medical history were associated with the outcome (P = 0.002 and P< 0.001, respectively). In multivariate Cox regression analysis, the continuous AF duration was the only independent predictor of recurrent arrhythmias (hazard ratio 1.17, 95% confidence interval 1.10–1.23, P < 0.001). In patients with AF duration of ≥3 years, the clinical success was comparable regardless of whether AF termination was achieved or not (log‐rank, P = 0.27). In the remaining patients with AF duration of <3 years, procedural AF termination was associated with a higher arrhythmia‐free rate than when AF was sustained after ablation (log‐rank, P = 0.023). Conclusion: Extensive ablation to terminate AF might not be warranted in patients with a longer AF duration. On the contrary, procedural AF termination could be associated with maintenance of sinus rhythm in patients with a shorter AF duration with a less proarrhythmic substrate. (PACE 2012;35:1436–1443)     

Predictive Capability of Left Atrial Size Measured by CT,TEE, and TTE for Recurrence of Atrial Fibrillation Following Radiofrequency Catheter Ablation

Background: Recurrence of atrial fibrillation (AF) after radiofrequency catheter ablation (RFCA) has been well established and is in part related to left atrial (LA) size. The purpose of this study was to assess the predictive capability of LA diameter (LAD) and LA volume (LAV) by echocardiography and computed tomography (CT) to determine success in patients undergoing RFCA of AF. Methods: Eighty‐eight patients with paroxysmal or persistent AF who had undergone RFCA and had a prior transthoracic echocardiogram (TTE), transesophageal echocardiogram (TEE), and CT were enrolled in the study. TTE LADs and LV ejection fraction as well as TEE LADs and LAVs in three views were recorded. CT LAVs were also recorded. Clinical parameters prior to ablation as well as at 1‐year follow‐up were assessed. Results: A total of 40 (45%) patients with paroxysmal AF and 48 (55%) patients with persistent AF were analyzed. Paroxysmal AF patients had a RFCA success rate of 88% at 1 year with persistent AF patients having a 52% success rate (P < 0.001). A CT‐derived LAV ≥ 117 cc was associated with an odds ratio (OR) for recurrence of 4.8 (95% confidence interval [CI]=[1.4–16.4], P = 0.01) while a LAV ≥130 cc was associated with an OR for recurrence of 22.0 (95% CI =[2.5–191.0], P = 0.005) after adjustment for persistent AF. Conclusions: LA dimensions and AF type are highly predictive of AF recurrence following RFCA. LAV by CT has significant predictive benefit over standard LADs in severely enlarged atria even after adjustment for AF type. (PACE 2010; 532–540)     

Clinical Impact of an Open‐Irrigated Radiofrequency Catheter with Direct Force Measurement on Atrial Fibrillation Ablation

Background: Electrode‐tissue contact is crucial for adequate lesion formation in radiofrequency catheter ablation (RFCA). Objective: We assessed the impact of direct catheter force measurement on acute procedural parameters during RFCA of atrial fibrillation (AF). Methods: Fifty consecutive patients (28 male) with paroxysmal AF who underwent their first procedure of circumferential pulmonary vein (PV) isolation (PVI) were assigned to either RFCA using (1) a standard 3.5‐mm open‐irrigated‐tip catheter or (2) a catheter with contact force measurement capabilities. Using the endpoint of PVI with entry and exit block, acute procedural parameters were assessed. Results: Procedural data showed a remarkable decline in ablation time (radiofrequency time needed for PVI) from 50.5 ± 15.9 to 39.0 ± 11.0 minutes (P = 0.007) with a reduction in overall procedure duration from 185 ± 46 to 154 ± 39 minutes (P = 0.022). In parallel, the total energy delivered could be significantly reduced from 70,926 ± 19,470 to 58,511 ± 14,655 Ws (P = 0.019). The number of acute PV reconnections declined from 36% to 12% (P = 0.095). Conclusions: The use of contact force sensing technology is able to significantly reduce ablation and procedure times in PVI. In addition, energy delivery is substantially reduced by avoiding radiofrequency ablation in positions with insufficient surface contact. Procedural efficacy and safety of this new feature have to be evaluated in larger cohorts. (PACE 2012; 35:1312–1318)     

Long‐Term Clinical Efficacy and Risk of Catheter Ablation for Atrial Fibrillation in Octogenarians

Background: Radiofrequency ablation is an effective treatment for atrial fibrillation (AF). With improved safety, the therapy has been offered to increasingly older populations. Arrhythmia mechanisms, medical comorbidities, and safety may vary in the very elderly population. Methods: Patients presenting for AF ablation were divided into two groups [≥80 years (n = 35), <80 years (n = 717)]. AF ablation consisted of pulmonary vein antral isolation with or without additional linear lesions. A successful outcome was defined as no further AF and off all antiarrhythmic medications >3 months following 1 + ablation procedures. Results: The type of AF was similar in both groups (paroxysmal: 46% in the older group vs 54% in the younger, P = 0.33). Older patients were more likely to have a higher CHADS2 score, coronary artery disease, and less likely to have had a prior ablation. The hospital stay on average was longer in the older cohort (2.9 ± 7.7 vs 2.1 ± 1.1 days, P = 0.001). There was no increased risk of peri‐procedural complications. One‐year survival free of AF or flutter was 78% in those >80 and 75% in those younger (P = 0.78). There was no difference between groups if the AF was paroxysmal (P = 0.44) or persistent/chronic (P = 0.74). Over a 3‐year follow‐up period, five patients died and four strokes occurred all in the younger cohort. Conclusion: Octogenarian patients, despite more coexistent cardiovascular diseases, have favorable outcomes after AF ablation measured by successful rhythm management. On an average their hospital stay is longer, but no significant increase in short‐ or long‐term complications was observed. These data support AF ablation in select octogenarians. (PACE 2010; 33:146–152)     

Atrial Flutter Ablation in Inducible Patients during Pulmonary Vein Atrum Isolation: A Randomized Comparison

Background: The incidence of atrial flutter (AFL) post pulmonary vein antrum isolation (PVAI) in patients with atrial fibrillation (AF) is reported to be between 8% and 20%. The need for right or left AFL ablation during the initial PVAI procedure remains controversial. We prospectively compared mapping and ablation versus no ablative treatment of inducible AFL during PVAI. Methods and Results: In 220 patients (167 men, mean age 56 ± 15 years) with symptomatic AF presenting for PVAI, burst pacing from the high right atrium and coronary sinus was performed to determine AFL inducibility. A total of 25 patients with sustained (17 patients) or reproducible (eight patients) AFL were included in this study. Patients were randomized to mapping and ablation of AFL using the CARTO 3D mapping system (Biosense Webster, Diamond Bar, CA, USA) versus no further ablation. Typical AFL was induced in 48% of the patients. During a follow‐up of 12 ± 4 months, recurrences were determined by serial 48‐h Holter and event monitors. Recurrence rates, time to recurrence, and AFL cycle length differences between both groups were not statistically significant. Conclusion: These data suggest that inducibility of AFL post PVAI does not predict long‐term incidence of AFL. Moreover, this study demonstrates little benefit to mapping and ablation of these arrhythmias during the PVAI procedures.     

Noninvasive Evidence of Shortened Atrial Refractoriness during Sinus Rhythm in Patients with Paroxysmal Atrial Fibrillation

Background: Shortening of the atrial refractory period is the key feature of atrial electrical remodeling during atrial fibrillation (AF). During sinus rhythm (SR), assessment of the atrial refractoriness is hampered by the fact that the atrial repolarization wave (Ta wave) is largely obscured by the following QRST complex. The purpose of this study was to study the Ta wave in subjects with paroxysmal AF during SR with third‐degree atrioventricular (AV) block, and in matched controls. Methods: Fifteen patients (mean age 70 ± 10 years, five males) with paroxysmal AF undergoing AV‐nodal ablation were studied. Fifteen age‐ and gender‐matched subjects (mean age 71 ± 9 years, five males) with third‐degree AV block, without a history of heart disease, were used as controls. Standard 12‐lead electrocardiograms (ECGs) were recorded and transformed to orthogonal leads and studied using P‐wave signal averaging technique. Results: The P to Ta interval was shorter (408 ± 47 ms vs 451 ± 53 ms, P = 0.017) and in Lead Y the Ta peak location was earlier (156 ± 31 ms vs 187 ± 34 ms, P = 0.002) in subjects with paroxysmal AF than in the controls. The P‐wave duration (126 ± 15 ms vs 129 ± 17 ms, P = 0.59) and morphology was similar in AF patients and controls. Conclusions: In this study, the ECG signs of shorter atrial refractoriness associated with a history of AF are visualized for the first time during SR. The finding of the earlier location of the PTa peak in AF subjects implies that a possible indicator of increased arrhythmia susceptibility may be visible already in the unprocessed ECG.     

Left Atrial Voltage during Atrial Fibrillation in Paroxysmal and Persistent Atrial Fibrillation Patients

Background: Left atrial (LA) endocardial voltage characteristics assessed during atrial fibrillation (AF) have not been previously compared in different AF types. This study was aimed at investigating the LA voltages and volumes in patients with paroxysmal and persistent AF. Methods: LA electroanatomic voltage maps acquired during AF were compared between consecutive patients without major structural heart disease undergoing first catheter ablation for paroxysmal AF (n = 100) or persistent AF (n = 100). The groups were comparable in baseline clinical characteristics. Results: Patients with persistent AF presented with lower median LA voltage (median 0.41, interquartile range [IQR] 0.31–0.51 mV versus median 0.99, IQR 0.47–1.56 mV; P < 0.001), and maximum LA voltage (4.07 ± 1.76 vs 6.42 ± 2.16 mV; P < 0.001). They also had a higher proportion of the LA points exhibiting voltage <0.2 mV (30 ± 20 vs 12 ± 11%; P < 0.001) and voltage 0.2–1.0 mV (55 ± 15 vs 42 ± 19%; P < 0.001). They further displayed higher LA volume/body surface area (75 ± 16 vs 58 ± 13 mL/m²; P < 0.001). In the multivariate regression model, both LA voltage (P < 10^?9) and LA volume (P < 10^?5) were significant determinants of AF type. Conclusion: Patients with persistent AF had significantly lower LA voltage compared with patients with paroxysmal AF even after adjustment for differences in indexed LA volume. LA voltage represents an independent covariate of clinical manifestation of AF. (PACE 2010; 541–548)     

Interatrial septum pacing decreases atrial dyssynchrony on strain rate imaging compared with right atrial appendage pacing

Background: Interatrial septum pacing (IAS‐P) decreases atrial conduction delay compared with right atrial appendage pacing (RAA‐P). We evaluate the atrial contraction with strain rate of tissue Doppler imaging (TDI) during sinus activation or with IAS‐P or RAA‐P. Methods: Fifty‐two patients with permanent pacemaker for sinus node disease were enrolled in the study. Twenty‐three subjects were with IAS‐P and 29 with RAA‐P. The time from end‐diastole to peak end‐diastolic strain rate was measured and corrected with RR interval on electrocardiogram. It was defined as the time from end‐diastole to peak end‐diastolic strain rate (TSRc), and the balance between maximum and minimum TSRc at three sites (ΔTSRc) was compared during sinus activation and with pacing rhythm in each group. Results: There were no significant differences observed in general characteristics and standard echocardiographic parameters except the duration of pacing P wave between the two groups. The duration was significantly shorter in the IAS‐P group compared with the RAA‐P group (95 ± 34 vs 138 ± 41; P = 0.001). TSRc was significantly different between sinus activation and pacing rhythm (36.3 ± 35.7 vs 61.6 ± 36.3; P = 0.003) in the RAA‐P group, whereas no significant differences were observed in the IAS‐P group (25.4 ± 12.1 vs 27.7 ± 14.7; NS). During the follow‐up (mean 2.4 ± 0.7 years), the incidence of paroxysmal atrial fibrillation (AF) conversion to permanent AF was not significantly different between the two groups. Conclusions: IAS‐P decreased the contraction delay on atrial TDI compared to RAA‐P; however, it did not contribute to the reduction of AF incidence in the present study. (PACE 2011; 34:370–376)     

Significant Left Atrial Appendage Activation Delay Complicating Aggressive Septal Ablation during Catheter Ablation of Persistent Atrial Fibrillation

Background: This study aims to describe significant left atrial appendage activation following ablation of persistent atrial fibrillation, and explore its relationship with aggressive septal ablation. Methods and Results: Significant left atrial appendage activation delay was found in 23 out of 201 patients undergoing persistent atrial fibrillation ablation. Of them, 14 were found in their index procedures, of whom septal line ablation was performed in nine (odds ratio 15.2, 95% confidence interval 4.6–50.8, P < 0.001). Another nine were found during their redo procedures (including two with biatrial activation dissociation), all of whom received extensive left septal complex fractionated electrograms ablation in their prior procedures (P = 0.002). Electrocardiograph showed split P wave with the latter component merged into the QRS wave. Activation mapping demonstrated the earliest breakthrough of the left atrium changed to coronary sinus in 18 (85.7%) patients. After 1 month, the mitral A wave velocity was 18.2 ± 17.0 cm/s, and decreased significantly as compared with preablation (20.2 ± 19.1 vs 58.2 ± 17.9 cm/s, P = 0.037) in patients undergoing redo procedures. Fourteen (60.9%) remained arrhythmia‐free during follow‐up for 10.6 ± 6.2 months. Conclusion: Septal line ablation and extensive septal complex fractionated electrograms ablation are correlated with significant left atrial activation delay or even biatrial activation dissociation, and should be performed with prudent consideration. (PACE 2010; 33:652–660)     

Termination of long-lasting persistent versus short-lasting persistent and paroxysmal atrial fibrillation by ablation

Background: Left atrial (LA) structures for the maintenance of different atrial fibrillation (AF) forms are not uniform. The incidence, electrophysiological patterns, and LA sites of sinus rhythm (SR) restoration during ablation of different AF forms were evaluated. Methods: One hundred patients with long‐lasting persistent AF were retrospectively compared to 35 patients with short‐lasting persistent AF and 59 patients with a sustained episode of paroxysmal AF. All patients underwent a first ablation using a stepwise ablation approach with the endpoint of SR restoration by ablation. Results: SR was restored in 38%, 83%, and 97% of patients with long‐lasting persistent, short‐lasting persistent, and paroxysmal AF, respectively (P <0.001 for long‐lasting persistent vs paroxysmal AF; P = 0.02 for long‐lasting persistent vs short‐lasting persistent AF). When modes and sites of SR restoration were evaluated among the patients with long‐lasting persistent, short‐lasting persistent, and paroxysmal AF, SR was restored via conversion into LA tachycardia in 79%, 52%, and 4% of patients (P <0.001 for long‐lasting persistent vs paroxysmal AF); by the pulmonary vein encircling in 8%, 24%, and 93% patients (P <0.001 for long‐lasting persistent vs paroxysmal AF); and by ablation at the LA anterior wall or inside the coronary sinus in 66%, 45%, and 2% patients (P <0.001 for long‐lasting persistent and paroxysmal AF). During the 31 ± 14 month follow‐up since the first ablation, of the 50 patients with long‐term SR maintenance (38 patients free of class I or III antiarrhythmic drugs), SR was restored by ablation in 29 (58%) patients versus nine (18%) patients out of 50 patients with unsuccessful clinical outcome (P = 0.009). Conclusion: Ablation of long‐lasting persistent AF was characterized by more frequent failure to restore SR, and predominant conversion into LA tachycardia prior to SR restoration, and SR restoration by ablation outside the LA posterior wall. SR restoration by ablation was associated with better clinical outcome in these patients.     

Assessment of Atrial Conduction Time in Patients with Familial Mediterranean Fever

Background: Increased inflammatory activity is known to be a pathophysiologic characteristic of atrial fibrillation. Familial Mediterranean fever (FMF) is a disease characterized by recurrent and sustained increased inflammatory activity. Atrial conduction abnormalities in these patients have not been investigated in terms of P‐wave duration, P‐wave dispersion (Pd), and atrial electromechanical delay measured by tissue Doppler echocardiography (TDE). We aimed to assess atrial conduction time in patients with FMF. Methods: A total of 33 patients with FMF (13 males/20 females, 28.4 ± 12.5 years), and 33 controls (13 males/20 females, 28.5 ± 12.1 years) were included. Atrial electromechanical coupling (PA) and intra‐ and interatrial electromechanical delay were measured with TDE. From the 12‐lead electrocardiogram Pd was calculated. Results: Atrial electromechanical coupling at the left lateral mitral annulus (PA lateral) was significantly higher in FMF patients (58.0 ± 9.0 vs 51.0 ± 5.8, P < 0.001). Interatrial (PA lateral–PA tricuspid) and intraatrial electromechanical delay (PA septum–PA tricuspid) were significantly longer in FMF patients (21.3 ± 7.4 vs 12.9 ± 4.6, P < 0.001 and 4.7 ± 5.5 vs 2.1 ± 1.7, P = 0.01, respectively). Also, Pd and maximum P‐wave duration were significantly higher in FMF patients (42.8 ± 7.9 vs 35.3 ± 6.1, P < 0.001 and 98.6 ± 9.0 vs 93.1 ± 8.5, P = 0.01, respectively). A positive correlation was detected between interatrial electromechanical delay and Pd (r = 0.622, P < 0.001). Plasma level of C‐reactive protein (CRP) correlated with interatrial electromechanical delay and Pd (r = 0.733, P < 0.001; and r = 0.427, P < 0.001, respectively). Conclusion: This study shows that atrial electromechanical delay and Pd are prolonged in FMF patients. Atrial electromechanical delay is closely associated with Pd and plasma level of CRP.     

Atrial fibrillation ablation using a closed irrigation radiofrequency ablation catheter

Background: Catheter ablation is an effective therapy for symptomatic, medically refractory atrial fibrillation (AF). Open‐irrigated radiofrequency (RF) ablation catheters produce transmural lesions at the cost of increased fluid delivery. In vivo models suggest closed‐irrigated RF catheters create equivalent lesions, but clinical outcomes are limited. Methods: A cohort of 195 sequential patients with symptomatic AF underwent stepwise AF ablation (AFA) using a closed‐irrigation ablation catheter. Recurrence of AF was monitored and outcomes were evaluated using Kaplan–Meier survival analysis and Cox proportional hazards models. Results: Mean age was 59.0 years, 74.9% were male, 56.4% of patients were paroxysmal and mean duration of AF was 5.4 years. Patients had multiple comorbidities including hypertension (76.4%), tobacco abuse (42.1%), diabetes (17.4%), and obesity (mean body mass index 30.8). The median follow‐up was 55.8 weeks. Overall event‐free survival was 73.6% with one ablation and 77.4% after reablation (reablation rate was 8.7%). Median time to recurrence was 26.9 weeks. AF was more likely to recur in patients being treated with antiarrhythmic therapy at the time of last follow‐up (recurrence rate 30.3% with antiarrhythmic drugs, 13.2% without antiarrhythmic drugs; hazard ratio [HR] 2.2, 95% confidence interval [CI] 1.1–4.4, P = 0.024) and in those with a history of AF greater than 2 years duration (HR 2.7, 95% CI 1.1–6.9, P = 0.038). Conclusions: Our study represents the largest cohort of patients receiving AFA with closed‐irrigation ablation catheters. We demonstrate comparable outcomes to those previously reported in studies of open‐irrigation ablation catheters. Given the theoretical benefits of a closed‐irrigation system, a large head‐to‐head comparison using this catheter is warranted. (PACE 2012; 35:506–513)     

Left Atrial Ablation at the Anatomic Areas of Ganglionated Plexi for Paroxysmal Atrial Fibrillation

Background: Modification of left atrial ganglionated plexi (GP) is a promising technique for the treatment of paroxysmal atrial fibrillation (AF) but its therapeutic efficacy is not established. This study aimed at evaluating the effectiveness of anatomic GP modification by means of an implantable arrhythmia monitoring device. Methods: In 56 patients with paroxysmal AF, radiofrequency ablation at anatomic sites, where the main clusters of GP have been identified in the left atrium, was performed. In all patients, an electrocardiogram monitor (Reveal XT, Medtronic Inc., Minneapolis, MN, USA) was implanted before (n = 7) or immediately after (n = 49) AF ablation. Results: Average duration of the procedure was 142 ± 18 min and average fluoroscopy time 20 ± 7 min. In total, 53–81 applications of RF energy were delivered (mean of 18.2 ± 3.8 at each of the four areas of GP ablation). Heart rate variability was assessed in 31 patients. Standard deviation of RR intervals over the entire analyzed period, the root mean square of differences between successive RR intervals, and high frequencies decreased, while HRmin, HRmean, and LF to HF ratio increased immediately postablation; these values returned to baseline 6 months after the procedure. At end of 12‐month follow‐up, 40 (71%) patients were free of arrhythmia recurrence. Ten patients had AF recurrence, two patients had left atrial flutter, and four patients had episodes of flutter as well as AF recurrence. Duration of episodes of AF after ablation gradually decreased over the follow‐up period. Conclusions: Regional ablation at the anatomic sites of the left atrial GP can be safely performed and enables maintenance of sinus rhythm in 71% of patients with paroxysmal AF for a 12‐month period. (PACE 2010; 33:1231–1238)     

Catheter Ablation for Paroxysmal Atrial Fibrillation: A Randomized Comparison between Multielectrode Catheter and Point‐by‐Point Ablation

Introduction: Catheter ablation for paroxysmal atrial fibrillation is widely used for patients with drug‐refractory paroxysms of arrhythmia. Recently, novel technologies have been introduced to the market that aim to simplify and shorten the procedure. Aim: To compare the clinical outcome of pulmonary vein (PV) isolation using a multipolar circular ablation catheter (PVAC group), with point‐by‐point PV isolation using an irrigated‐tip ablation catheter and the CARTO mapping system (CARTO group; CARTO, Biosense Webster, Diamond Bar, CA, USA). Methods: Patients with documented PAF were randomized to undergo PV isolation using PVAC or CARTO. Atrial fibrillation (AF) recurrences were documented by serial 7‐day Holter monitoring. Results: One hundred and two patients (mean age 58 ± 11 years, 68 men) were included in the study. The patients had comparable baseline clinical characteristics, including left atrial dimensions and left ventricular ejection fraction, in both study arms (PVAC: n = 51 and CARTO: n = 51). Total procedural and fluoroscopic times were significantly shorter in the PVAC group (107 ± 31 minutes vs 208 ± 46 minutes, P < 0.0001 and 16 ± 5 minutes vs 28 ± 8 minutes, P < 0.0001, respectively). The AF recurrence was documented in 23% and 29% of patients in the PVAC and CARTO groups, respectively (P = 0.8), during the mean follow‐up of 200 ± 13 days. No serious complications were noted in both study groups. Conclusions: Clinical success rates of PV isolation are similar when using multipolar circular PV ablation catheter and point‐by‐point ablation with a three‐dimensional (3D) navigation system in patients with PAF, and results in shorter procedural and fluoroscopic times with a comparable safety profile. (PACE 2010; 33:1039–1046)     

Impact of Right Ventricular Pacing Sites on Exercise Capacity during Ventricular Rate Regularization in Patients with Permanent Atrial Fibrillation

Background: The deleterious effects of right ventricular apical (RVA) pacing may offset the potential benefit of ventricular rate (VR) regularization and rate adaptation during an exercise in patient's atrial fibrillation (AF). Methods: We studied 30 patients with permanent AF and symptomatic bradycardia who receive pacemaker implantation with RVA (n = 15) or right ventricular septal (RVS, n = 15) pacing. All the patients underwent an acute cardiopulmonary exercise testing using VVI‐mode (VVI‐OFF) and VVI‐mode with VR regularization (VRR) algorithm on (VVI‐ON). Results: There were no significant differences in the baseline characteristics between the two groups, except pacing QRS duration was significantly shorter during RVS pacing than RVA pacing (138.9 ± 5 vs 158.4 ± 6.1 ms, P = 0.035). Overall, VVI‐ON mode increased the peak exercise VR, exercise time, metabolic equivalents (METs), and peak oxygen consumption (VO₂max), and decreased the VR variability compared with VVI‐OFF mode during exercise (P < 0.05), suggesting that VRR pacing improved exercise capacity during exercise. However, further analysis on the impact of VRR pacing with different pacing sites revealed that only patients with RVS pacing but not patients with RVA pacing had significant increased exercise time, METs, and VO₂max during VVI‐ON compared with VVI‐OFF, despite similar changes in peaked exercise VR and VR variability. Conclusion: In patients with permanent AF, VRR pacing at RVS, but not at RVA, improved exercise capacity during exercise.     

Electrophysiological abnormalities occur prior to the development of clinical episodes of atrial fibrillation: observations from human epicardial mapping

Background: Atrial fibrillation (AF) is characterized by irregular atrial activation maintained by an arrhythmogenic substrate. We addressed the hypothesis that the substrate of human AF includes changes in atrial conduction properties. Methods: Patients in sinus rhythm (SR) and permanent AF undergoing cardiac surgery underwent right atrial epicardial mapping. AF was induced by burst pacing in patients in SR and was defined as sustained at >30 seconds. Epicardial maps were analyzed to determine conduction properties, AF activation patterns, and refractoriness. Patients in SR underwent postoperative Holter monitoring. Results: Thirty‐seven subjects were recruited. (27 in SR and 10 in permanent AF). Sustained AF was induced in 17 patients in SR. Only patients with sustained AF developed any episodes of postoperative AF (P < 0.05), indicating the preexistence of an arrhythmogenic substrate, which was characterized by prolonged unipolar electrograms (37.0 ± 9.4 ms vs 27.5 ± 6.4 ms, P = 0.03), particularly in the region of the crista terminalis (41.2 ms ± 12.1 vs 26.7 ms ± 5.8, P = 0.004) compared with the nonsustaining group. However, these differences in electrogram characteristics were not associated with changes in wavefront propagation velocity (WPV) during SR or pacing. Activation mapping of acutely induced AF was compared with permanent AF and although there were shorter mean fibrillation intervals in permanent AF (171 ± 16 ms vs 229 ± 51 ms, P < 0.001), there was no difference in fibrillatory activation pattern (complexity scores: 2.21 ± 0.52 vs 2.02 ± 0.61) or WPV (46.9 ± 15.4 cm/s vs 53.5 ± 17.6 cm/s, P = 0.37). Fibrillatory activation pattern was associated with both WPV (P = 0.03) and wavelength (P = 0.03) in both pacing‐induced and permanent AF. Conclusions: Patients in SR capable of sustaining pacing‐induced AF have differences in electrogram duration, which are apparent before clinical episodes of AF. Although patients with permanent AF had shortening of refractoriness, there was no evidence of further changes in fibrillatory activation pattern or macroscopic wavefront propagation velocity in permanent AF. These results imply that changes occur before the onset of AF and indicate the presence of a substrate capable of maintaining AF with only alterations in refractoriness required for the development of permanent AF.     

Ventricular Pauses during Atrial Fibrillation Predict Relapse after Electrical Cardioversion: A Prospective Study

Aims: To investigate the use of ambulatory electrocardiogram (ECG) monitoring in atrial fibrillation (AF) to predict recurrence after electrical cardioversion (ECV). Methods: RR interval variables were obtained from 24 hours ECGs recorded before ECV in 119 patients (85 men, age 66 ± 10 years) with persistent AF. Patients were followed for 1 month. Results: Of the 119 patients, 16 (13%) failed ECV and 65 (55%) were in AF at 1 week and 81 (68%) at 1 month after ECV. The maximum RR interval (RR‐max) and the minimum RR interval (RR‐min) during AF were found to be reproducible. The RR‐max was longer in those who had AF 1 week (2.55 ± 0.49 vs 2.01 ± 0.52 seconds, P = 0.005) and 1 month (2.56 ± 0.50 vs 1.89 ± 0.43 ms; P < 0.001) after ECV than in those who maintained sinus rhythm. Those in AF at 1 month included more patients with RR‐max ≥ 2.8 seconds (31% vs 11% P = 0.021). The average heart rate was lower in patients with RR‐max ≥ 2.8 seconds, but the average rate was not predictive of AF recurrence. Conclusion: Ventricular pauses during AF predict relapse after ECV. (PACE 2010; 934–938)     

The influence of atrial and ventricular pacing on the incidence of atrial fibrillation: a meta-analysis

Background: The effect of atrial pacing on the incidence of atrial fibrillation (AF) is unknown. Furthermore, the threshold of ventricular pacing that is associated with a higher incidence of AF has yet to be determined. Thus, we set out to determine the optimal pacing modality in patients with sinus node dysfunction (SND) for the prevention of AF. Methods: Individual patient data from four contemporary pacemaker studies were gathered and analyzed. Since AF would inherently lead to a reduction in atrial pacing, percent atrial and ventricular pacing (%AP and %VP) were determined at the first follow‐up visit and then used as a surrogate for all endpoints. Patients with >5 minutes of AF at the first visit were excluded. The primary endpoint was defined as 7 consecutive days of AF. Results: A total of 1,507 patients were included. During a mean follow‐up of 14.3 ± 8.7 months, 77 patients developed AF (annual rate of 4.3%). The incidence of AF in the first (0–32%), second (32–66%), third (66–89%), and fourth (89–100%) quartiles of %AP was 1.3%, 5.3%, 5.8%, and 8.0%, respectively (P < 0.001). A multivariable analysis found that pacing above the first quartile was associated with a relative risk of 2.93 (95% confidence interval 1.16–7.39, P = 0.023). The grouping of %VP into first (0–2%), second (2–7%), third (7–84%), and fourth (84–100%) quartiles yielded an AF incidence of 2.4%, 3.4%, 6.6%, and 8.0%, respectively (P = 0.001). Conclusion: We demonstrated that in patients with SND both atrial and ventricular pacing are associated with a higher incidence of AF. (PACE 2011; 34:1593–1599)     

Noncavotricuspid isthmus-dependent right atrial tachycardia after paroxysmal atrial fibrillation ablation

Background: Atrial tachycardia (AT) is commonly encountered after atrial fibrillation (AF) ablation. But no study exclusively on noncavotricuspid isthmus‐dependent right AT (NCTI‐RAT) post‐AF ablation has been reported. The present study aims to describe its prevalence, electrophysiological mechanisms, and ablation strategy and to further discuss its relationship with AF. Methods: From July 2006 to November 2009, 350 consecutive patients underwent catheter ablation for paroxysmal AF. A total of seven patients (2.0%) developed NCTI‐RAT after left atrium ablation for AF. In these highly selected patients (two male, mean age 54 ± 11 years, mean left atrium diameter of 34 ± 7 cm), all had circumferential pulmonary vein isolation in their initial procedures and three of them had additional complex fractionated electrograms ablation in the left atrium and the coronary sinus. Results: Totally, nine NCTI‐RATs were mapped and successfully ablated in the right atrium with a mean cycle length of 273 ± 64 ms in seven patients. Five ATs in three patients were electrophysiologically proved to be macroreentry and the remaining four were focal activation. All the ATs were successfully abolished by catheter ablation. After a mean follow‐up of 29 ± 15 months post‐AT ablation, all patients were free of AT and AF off antiarrhythmic drugs. Conclusions: NCTI‐RAT is relatively less common post‐AF ablation. Totally, 2.0% of paroxysmal AF patients were revealed to have NCTI‐RAT. (PACE 2011; 34:391–397)     

Clinical Results of Far‐Field R‐Wave Reduction with a Short Tip‐Ring Electrode

Background: Far‐field R‐wave (FFRW) sensing of the atrial lead of AAI or DDD pacemakers causes incorrect mode switches and remains a problem in patients with atrial arrhythmias in whom low voltage sensing is essential. We studied a pacing electrode with a short tip‐ring distance (1.1 mm). We compared our findings with recordings from a conventional electrode with a larger tip‐ring distance (10 mm). Methods: Thirty‐six consecutive patients with an indication for DDD pacing were implanted with the short tip‐ring electrode. Another 23 patients received the conventional electrode. FFRW and P‐wave amplitudes during pacing and intrinsic ventricular depolarization were measured at implantation. Measurements were repeated before hospital discharge and at follow‐up between 10 and 14 days after implantation. Results: P‐wave amplitude was slightly smaller in the short tip‐ring group (2.71 ± 1.04 vs 3.17 ± 1.30 mV in the conventional group, respectively, P = NS). All P‐waves exceeded 1.2 mV. FFRW during pacing was 0.07 ± 0.05 in the short tip‐ring group and 0.54 ± 0.32 mV in the conventional group (P < 0.001). FFRW during intrinsic rhythm was 0.08 ± 0.04 and 0.55 ± 0.31 mV, respectively (P < 0.001). The ratio between P‐wave and FFRW was 48.6 ± 27.2 in the short tip‐ring group and 7.3 ± 4.4 in the conventional group (P < 0.001). FFRW and P‐wave amplitudes did not change at hospital discharge or during follow‐up. Conclusion: FFRW can be suppressed without compromising P‐wave sensing by using a pacing electrode with a short tip‐ring distance. Whether reduced FFRW amplitude results in clinical endpoints remains to be determined.