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Background— Pulmonary vein (PV) –encircling radiofrequency ablation frequently is effective in vagal atrial fibrillation (AF), and there is evidence that PVs may be particularly prone to cholinergically induced arrhythmia mechanisms. However, PV ablation procedures also can affect intracardiac autonomic ganglia. The present study examined the relative role of PVs versus peri-PV autonomic ganglia in an experimental vagal AF model. Methods and Results— Cholinergic AF was studied under carbachol infusion in coronary perfused canine left atrial PV preparations in vitro and with cervical vagal stimulation in vivo. Carbachol caused dose-dependent AF promotion in vitro, which was not affected by excision of all PVs. Sustained AF could be induced easily in all dogs during vagal nerve stimulation in vivo both before and after isolation of all PVs with encircling lesions created by a bipolar radiofrequency ablation clamp device. PV elimination had no effect on atrial effective refractory period or its responses to cholinergic stimulation. Autonomic ganglia were identified by bradycardic and/or tachycardic responses to high-frequency subthreshold local stimulation. Ablation of the autonomic ganglia overlying all PV ostia suppressed the effective refractory period–abbreviating and AF-promoting effects of cervical vagal stimulation, whereas ablation of only left- or right-sided PV ostial ganglia failed to suppress AF. Dominant-frequency analysis suggested that the success of ablation in suppressing vagal AF depended on the elimination of high-frequency driver regions. Conclusions— Intact PVs are not needed for maintenance of experimental cholinergic AF. Ablation of the autonomic ganglia at the base of the PVs suppresses vagal responses and may contribute to the effectiveness of PV-directed ablation procedures in vagal AF.

Background Mapping criteria for hemodynamically tolerated, postinfarction ventricular tachycardia (VT) have been evaluated in only small series of patients. Objectives The purpose of this study was to evaluate the utility of various mapping criteria for identifying a critical VT circuit isthmus in a post hoc analysis. Methods Ninety VTs (cycle length 491 ± 84 ms) were mapped in 48 patients with a prior myocardial infarction. The mapping catheter was positioned within a protected area of the reentrant circuit of the targeted VTs at 176 sites. All sites showed concealed entrainment. The predictive values of the following mapping criteria for a successful ablation site were compared: discrete isolated potential during VT, inability to dissociate the isolated potential from the VT, endocardial activation time >70 ms, matching electrogram-QRS and stimulus-QRS intervals, VT termination without global capture during pacing, stimulus-QRS/VT cycle length ratio ≤0.7, and postpacing interval. For each criterion, the receiver operating characteristic curve was constructed, and the area under the curve was calculated to assess the discriminatory value of the criterion. Results Seventy-eight of 90 VTs (87%) were successfully ablated. The area under the receiver operating characteristic curve was largest (0.89) for matching stimulus-QRS and electrogram-QRS intervals. In combination with an isolated potential that could not be dissociated from the VT, the area under the receiver operating characteristic curve increased to 0.93. Conclusion At sites with concealed entrainment, matching stimulus-QRS and electrogram-QRS intervals were superior to other criteria in differentiating a critical isthmus from bystander or noncritical sites in postinfarction VT.

Objectives The aim of this study was to describe the extent of esophageal mobility that occurs during catheter ablation for atrial fibrillation under conscious sedation. Background Ablation along the posterior left atrium may cause an atrioesophageal fistula. One strategy for avoiding this risk is to not deliver radiofrequency energy at sites in contact with the esophagus. Methods In 51 consecutive patients with atrial fibrillation who underwent left atrial ablation under conscious sedation, digital cine-fluoroscopic imaging of the esophagus was performed in two views after ingestion of barium paste at the beginning and end of the ablation procedure. Movement of the esophagus was determined at the superior, mid-, and inferior parts of the posterior left atrium in reference to the spine. Results Mean esophageal movement was 2.0 ± 0.8 cm (range = 0.3 to 3.8 cm) at the superior, 1.7 ± 0.8 cm (range = 0.1 to 3.5 cm) at the mid-, and 2.1 ± 1.2 cm (range = 0.1 to 4.5 cm) at the inferior levels. In 67% of the 51 patients, the esophagus shifted by ≥2 cm, and in 4% there was ≥4 cm of lateral movement. The mean change in esophageal luminal width was 5 ± 7 mm (range = 0 to 36 mm) at the superior, 5 ± 7 mm (range = 0 to 32 mm) at the mid-, and 6 ± 7 mm (range = 0 to 21 mm) at the inferior levels of the posterior left atrium. Conclusions The esophagus often is mobile and shifts sideways by ≥2 cm in a majority of patients undergoing catheter ablation for atrial fibrillation under conscious sedation. Therefore, real-time imaging of the esophagus may be helpful in reducing the risk of esophageal injury during radiofrequency ablation along the posterior left atrium.

Background The effects of left atrial (LA) circumferential ablation on LA function in patients with atrial fibrillation (AF) have not been well described. Objectives The purpose of this study was to determine the effect of LA circumferential ablation on LA function. Methods Gated, multiphase, dynamic contrast-enhanced computed tomographic (CT) scans of the chest with three-dimensional reconstructions of the heart were used to calculate the LA ejection fraction (EF) in 36 patients with paroxysmal (n = 27) or chronic (n = 9) AF (mean age 55 ± 11 years) and in 10 control subjects with no history of AF. Because CT scans had to be acquired during sinus rhythm, a CT scan was available both before and after (mean 5 ± 1 months) LA circumferential ablation (LACA) in only 10 patients. A single CT scan was acquired in 8 patients before and in 18 patients after LACA ablation. Radiofrequency catheter ablation was performed using an 8-mm-tip catheter to encircle the pulmonary veins, with additional lines along the mitral isthmus and the roof. Results In patients with paroxysmal AF, LA EF was lower after than before LACA (21% ± 8% vs 32 ± 13%, P = .003). LA EF after LA catheter ablation was similar among patients with paroxysmal AF and those with chronic AF (21% ± 8% vs 23 ± 13%, P = .7). However, LA EF after LA catheter ablation was lower in all patients with AF than in control subjects (21% ± 10% vs 47% ± 5%, P Conclusion During medium-term follow-up, restoration of sinus rhythm by LACA results in partial return of LA function in patients with chronic AF. However, in patients with paroxysmal AF, LA catheter ablation results in decreased LA function. Whether the impairment in LA function is severe enough to predispose to LA thrombi despite elimination of AF remains to be determined.

Objectives The goal of this study was to describe the prevalence and ablation of coronary sinus (CS) arrhythmias after left atrial ablation for atrial fibrillation (AF). Background The CS has been implicated in a variety of supraventricular arrhythmias. Methods Thirty-eight patients underwent mapping and ablation of atypical flutter that developed during (n = 5) or after (n = 33) ablation for AF. Also included were two patients with focal CS arrhythmias that occurred during an AF ablation procedure. A tachycardia was considered to be originating from the CS if the post-pacing interval in the CS matched the tachycardia cycle length and/or if it terminated during ablation in the CS. Results Among the 33 patients who developed atypical flutter late after AF ablation, 9 (27%) were found to have a CS origin. Overall, 16 of the 40 patients in this study had a CS arrhythmia. The tachycardia was macro-re-entrant in 14 patients (88%) and focal in two patients. Radiofrequency ablation with an 8-mm-tip catheter was successful in 15 patients (94%) without complication. In eight patients (50%), ≥45 W was required for successful ablation. Thirteen of the 15 patients (87%) with a successful ablation acutely remained arrhythmia-free during 5 ± 5 months of follow-up. Conclusions The musculature of the CS serves as a critical component of the re-entry circuit in approximately 25% of patients with atypical flutter after ablation for AF. The CS may also generate focal atrial arrhythmias that may play a role in triggering and/or maintaining AF. Catheter ablation of these arrhythmias in the CS can be performed safely.

Background Mechanical trauma has been described as a helpful guide for ablation of atrial tachycardias and accessory pathways. In postinfarction ventricular tachycardia (VT), the reentrant circuit is partly endocardial and therefore may be susceptible to catheter trauma. Objectives The purpose of this study was to determine the prevalence and significance of VT termination resulting from catheter trauma. Methods A consecutive series of 39 patients (mean age 68 ± 7 years, ejection fraction 0.25 ± 0.02) underwent left ventricular mapping for postinfarction VT. Mapping was performed during 62 hemodynamically tolerated VTs (mean cycle length 451 ± 88 ms). Only hemodynamically tolerated VTs that did not terminate spontaneously and VTs that were reproducibly inducible were included in the study. VT termination was considered mechanical only if it was not caused by a premature depolarization. Results In 13 of 62 VTs (21%) in 8 of 39 patients (21%), either VT terminated during catheter placement at a particular site (n = 7) or a previously reproducibly inducible VT became no longer inducible with the mapping catheter located at a particular site (n = 6). The stimulus-QRS interval was significantly shorter at sites where mechanical trauma affected the reentrant circuit compared with sites having concealed entrainment (102 ± 56 ms vs 253 ± 134 ms, P = .003). At the site that was susceptible to mechanical trauma, the pace map was identical or highly similar in 13 of 13 VTs. After radiofrequency ablation at these sites, the targeted VTs were no longer inducible. No patient had recurrence of the targeted VT during a mean follow-up of 15 ± 11 months. Conclusions Catheter contact at a critical endocardial site can interrupt postinfarction VT or prevent its induction. Radiofrequency ablation at sites of mechanical termination of VT has a high probability of success.

Objectives The purpose of this study was to determine the prevalence and clinical significance of macroreentrant atrial tachycardia (AT) after left atrial (LA) circumferential ablation for atrial fibrillation (AF). Background Linear ablation for AF may result in macroreentrant AT. Methods Three hundred forty-nine patients (age 54 ± 11 years) underwent LA circumferential ablation for AF (paroxysmal in 227). Ablation lines were created around the left-sided and right-sided pulmonary veins, with additional ablation lines in the posterior LA and mitral isthmus. If macroreentrant AT was observed acutely in the electrophysiology laboratory, it was not ablated. If an organized AT occurred during follow-up, the initial strategy was rate control. If AT persisted for > 3 to 4 months, catheter ablation was performed. Results Seventy-one patients (20%) had spontaneous or induced macroreentrant AT (cycle length 244 ± 31 ms) in the electrophysiology laboratory following LA circumferential ablation. During follow-up, 85 patients (24%) experienced spontaneous AT (cycle length 238 ± 35 ms) at a mean of 44 ± 62 days following LA circumferential ablation. Among the 71 patients with macroreentrant AT acutely following LA circumferential ablation, 39 (55%) developed AT during follow-up. Among the 85 patients with AT during follow-up, the tachycardia remitted without a repeat ablation procedure in 28 patients (33%), most commonly within 5 months. Twenty-eight of the 349 patients (8%) underwent a repeat ablation procedure for AT. The critical isthmus was localized to the mitral isthmus in 17 of 28 patients (61%). Conclusions Macroreentrant AT is a common form of proarrhythmia after LA circumferential ablation for AF. Because it may resolve spontaneously, ablation of AT should be deferred for several months.

The purpose of this prospective study was to compare radiofrequency catheter ablation of the cavotricuspid isthmus using a strictly anatomic approach to an approach guided by a bipolar voltage map to avoid high voltage zones in the cavotricuspid isthmus.It is not clear whether local atrial electrogram amplitude influences the achievement of complete cavotricuspid isthmus block during radiofrequency catheter ablation for atrial flutter.Thirty-two patients with atrial flutter were randomized to cavotricuspid isthmus ablation using an anatomical approach (group I, 16 patients) or guided by a bipolar voltage map (group II, 16 patients). A 3-dimensional electroanatomic mapping system and an 8-mm-tip ablation catheter were used in all patients. With the anatomical approach, an ablation line was created in the cavotricuspid isthmus at a 6 o'clock position in the 45 degree left anterior oblique projection. During voltage-guided ablation, a high-density bipolar voltage map of the cavotricuspid isthmus was created, and then contiguous applications of radiofrequency energy were delivered to create an ablation line through the cavotricuspid isthmus sites with the lowest bipolar voltage.Complete cavotricuspid isthmus conduction block was achieved in 100% of patients in each group. The mean maximum voltages along the line were 3.6 +/- 1.5 mV in group I, and 1.2 +/- 0.9 mV in group II (P.01). Creating a high-density voltage map was associated with approximately 15-minute increase in the total procedure time (P = .2). During a mean follow-up of 177 +/- 40 days, there were no recurrences of atrial flutter in either group. There were no complications in either group.When cavotricuspid isthmus ablation for atrial flutter is performed with an 8-mm-tip catheter, complete block can be achieved in all patients regardless of local voltage. Ablation of high voltage zones is not associated with a higher recurrence rate. Therefore, anatomic ablation without voltage mapping is the preferred initial approach for cavotricuspid isthmus ablation.

Background: Atrial fibrillation (AF) may have a ventricular proarrhythmic effect, particularly in the setting of heart failure. We assessed whether AF predicts appropriate implantable cardioverter-defibrillator (ICD) shocks in patients with left ventricular dysfunction and explored modulators of risk. Methods and Results: A retrospective cohort study was conducted on 215 consecutive patients with ICDs for primary prevention having a left ventricular ejection fraction ≤ 35%. Mean age at ICD implantation was 61.0 ± 9.7 years and 17% were women. Overall, 22 patients (10.2%) experienced appropriate ICD shocks over a follow-up of 1.3 ± 0.7 years, corresponding to an actuarial event-rate of 5.8% per year. In univariate analysis, AF was associated with a 3.6-fold increased risk of appropriate shocks (P = 0.0037). Annual rates of appropriate ICD shocks in patients with and without AF were 12.9% and 3.5%, respectively (P = 0.0200). In multivariate stepwise Cox regression analyses controlling for baseline imbalances, demographic parameters, underlying heart disease, and therapy, history of AF independently predicted appropriate shocks (hazard ratio 2.7, P = 0.0278). Prolonged QRS duration (>130 ms) and QTc (>440 ms) modulated the effect of AF on appropriate shocks. Patients with both AF and QRS > 130 ms were more than five times more likely to receive an appropriate ICD shock (hazard ratio 5.4, P = 0.0396). Patients with AF and QTc > 440 ms experienced a greater than 12-fold increased risk of appropriate shocks (hazard ratio 12.7, P = 0.0177). Conclusion: In prophylactic ICD recipients with left ventricular dysfunction, AF is associated with increased risk for ventricular tachyarrhythmias, particularly when combined with conduction and/or repolarization abnormalities.

Background: Atrial fibrillation (AF) is associated with appropriate ICD discharges in patients with primary prevention indications. We explored potential effect modifiers impacting on ventricular arrhythmogenic risk associated with AF. Methods and Results: A retrospective cohort study was conducted on 215 consecutive patients with ICDs for primary prevention having a left ventricular ejection fraction (LVEF) < 35% and followed for 1.3±0.7 years. Mean age was 61.0±0.7 years and 17% were women. Cox regression models were explored in subgroups of patients stratified by demographic parameters, prior medical and surgical history, physical exam features, laboratory findings, and results of diagnostic tests. Appropriate ICD discharges were received by 10% of patients. AF was associated with a 3.5 fold increased risk [95% CI (1,5, 8.1), P=0.005]. Effect modifiers for the relationship between AF and appropriate ICD discharges included QRS duration and QTc. In patients with a QRS>130 msec (N=93), 6 of 33 (18%) patients with AF received appropriate ICD discharges versus 2 of 60 (3%) without AF (P=0.03). In this subgroup, AF was associated with a hazard ratio of 5.1 (P=0.049). Among individuals with a QTc >440 msec (N=93), 6 of 32 (19%) AF patients received appropriate ICD discharges versus 1 of 61 (2%) without AF (P=0.01). AF was associated with a hazard ratio of 10.3 (P=0.031). Five of 28 patients (18%) with both prolonged QRS and QTc duration (N=77) that also having AF received appropriate ICD discharges compared to 0 of 49 of patients without AF (P=0.005). After adjusting for medical therapy, AF independently predicted appropriate ICD discharges in subgroups with and without QRS and QTc increase. Conclusion: AF portends increased risk for ventricular tachyarrhythmias in patients with heart failure, particularly when associated with conduction and/or repolarization abnormalities. This finding may reflect common depolarization and repolarization defects associated with the arrhythmic milieu contributing to AF and ventricular arrhythmias, or adverse consequences of AF on the complex neurohumoral/electrophysiological substrate underlying ventricular arrhythmogenesis in heart failure.

Background : Pulmonary vein (PV) activity is crucial in some forms of clinical atrial fibrillation (AF), particularly paroxysmal lone AF. The precise importance of PVs in AF associated with structural heart disease is less clear. Some evidence suggests that PVs may be important for AF in experimentally-remodeled atrial substrates, e.g. atrial-tachycardia remodeling (ATR) and congestive heart failure (CHF)-induced structural remodeling, but contradictory findings also exist. This study assessed the role of PVs in canine remodeling-associated AF by evaluating the changes induced by PV-LA disconnection via encircling epicardial ablation. Methods: AF was induced before and after complete isolation of all PVs in dogs with: ATR induced by atrial tachypacing (400 bpm x 1 wk; with AV block and 80 bpm ventricular pacing to control ventricular rate, n=5); and CHF induced by ventricular tachypacing (VTP, 240 bpm x 2 wks, n=7). Electrophysiological measurements and AF mapping with 240 unipolar atrial electro-grams in both atria and all PVs were also obtained before and after PV isolation. Results ATR reduced atrial ERPs and ERP rate adaptation. The shortest AF cycle length (AFCL) in each ATR dog was recorded from PVs (mean 84±3 ms), but the mean AFCL in each of the PVs (range 97–103 ms) was not different from the mean AFCL at LA sites (98 –103 ms). PV ablation did not affect AF duration in ATR dogs (mean 284±265 pre- vs. 304±225 s post-ablation, P=NS), nor did it significantly alter RA or LA AFCL. In CHF dogs, ERPs and ERP rate adaptation were preserved. The shortest AFCL was recorded in PVs in 2 dogs (108,112 ms) and in the left side of Bachmann’s bundle in 3 (97–117 ms). PV ablation failed to alter AF duration in CHF dogs (mean 778±203 pre- vs. 644±206 s post-ablation), and increased AFCL in RA and LA slightly (10 –15%) but not significantly. Conclusions : Uncoupling of the PVs from the LA fails to significantly affect the AF substrate in 2 clinically-relevant animal paradigms of AF-promoting atrial remodeling. These findings suggest that in the presence of a favorable atrial substrate for AF the PVs are not needed for AF maintenance, and are consistent with clinical observations that complete PV isolation may not be essential for effective ablation therapy of all groups of AF patients.

Background: Vagal (VG) and atrial tachycardia remodeled (ATR) AF substrates share many features: reduced effective refractory period (ERP), increased ERP heterogeneity and some common molecular mechanisms (I KACh enhancement by acetylcholine release in VG, constitutive I KACh enhancement in ATR). This study compared VG and ATR substrates at comparable ERP abbreviation. Methods: In each of 5 VG dogs, bilateral cervical VG stimulation parameters were adjusted (mean±SD: 3.6±1.7 V and 12.2±1.5 Hz; 0.2 ms) to produce the same mean ERP (at 4 RA and 4 LA sites) as a sex and weight matched ATR dog (RA paced 400 bpm × 7 days). Mean duration of burst pacing induced AF (DAF) and local dominant frequencies (DFs, analyzed by FFT at 240 bipolar electrodes, Fig A ) were determined. Results: Mean ERP was 79±13 ms in VG and 78±13 ms in ATR dogs. DAF was greater in VG than ATR dogs (1056±323 vs 289±510 s *P control, 43±61 s). Despite matched ERPs, there were significant differences in DF distribution (Fig B ): DF was faster (mean DF: 11.8±1.1 Hz VG vs 9.7±1.3 Hz ATR*) and DF variability greater (indicated by SD: 1.8±0.6 Hz VG vs 0.8±0.5 Hz ATR*) in VG dogs. AF drivers reflected by maximum DF zones were adjacent to autonomic ganglia (over RA in 4/5) for VG dogs; in ATR dogs driver zones were less clear and showed variable location. Conclusions: For a comparable atrial ERP, VG AF is faster and more persistent than AF with an ATR substrate. These results are consist with modeling work suggesting that VG-induced hyperpolarization is an important contributor to AF-maintaining rotor stabilization and acceleration, and indicate important differences between these superficially similar AF substrates.

Background— Because the genesis of atrial fibrillation (AF) is multifactorial and variable, an ablation strategy that involves pulmonary vein isolation and/or a particular set of ablation lines may not be equally effective or efficient in all patients with AF. A tailored strategy that targets initiators and drivers of AF is a possible alternative to a standardized lesion set. Methods and Results— Catheter ablation was performed in 153 consecutive patients (mean age, 56±11 years) with symptomatic paroxysmal AF with the use of an 8-mm tip radiofrequency ablation catheter. The esophagus was visualized with barium. The pulmonary veins and left atrium were mapped during spontaneous or induced AF. Arrhythmogenic pulmonary veins were isolated or encircled. If AF was still present or inducible, complex electrograms in the left atrium, coronary sinus, and superior vena cava were targeted for ablation. The end point of ablation was absence of frequent atrial ectopy and spontaneous AF during isoproterenol infusion and noninducibility of AF. Routine energy applications near the esophagus were avoided. During follow-up, left atrial flutter developed in 19% of patients and was still present in 10% at >12 weeks of follow-up. A repeat ablation procedure was performed in 18% of patients. During a mean follow-up of 11±4 months, 77% of patients were free from AF and/or atrial flutter without antiarrhythmic drug therapy. Pericardial tamponade or transient neurological events occurred in 2% of procedures. Conclusions— A tailored ablation strategy that only targets triggers and drivers of AF is feasible and eliminates paroxysmal AF in ≈80% of patients.

Background The coronary sinus (CS) and its branches may play a role in the genesis of various arrhythmias. Applications of radiofrequency energy within the CS may be necessary. Atrio-esophageal fistula has been recognized as a complication of ablation along the posterior left atrial wall. Objectives The purpose of this study was to describe the in vivo topographic anatomy of the CS, esophagus, and coronary arteries using computed tomography (CT). Methods Helical contrast CT of the heart with three-dimensional and endoscopic reconstructions was performed in 50 patients (28 men and 22 women; mean age 54 ± 10 years). The images were reformatted to determine the relationships among the CS, adjacent blood vessels, and esophagus and to determine the nature and thickness of surrounding tissue layers. Results Mean CS ostium diameter was 12 ± 4 mm, and mean thickness of the periosteal fat layer was 3 ± 2 mm. In 40 of the 50 patients (80%), the esophagus was adjacent to the CS, starting 24 ± 9 mm from the ostium, and remained in contact for a mean length of 7 ± 5 mm. Mean thickness of the fat layer between the esophagus and CS was 1 ± 1 mm, and mean thickness of the anterior wall of the esophagus was 3 ± 2 mm. In 10 patients (20%), there was no contact between the esophagus and CS. In 40 patients (80%), the right coronary artery was less than 5 mm from the CS (minimum distance 1 ± 1 mm) over a mean length of 17 ± 11 mm. In all patients, the circumflex artery was less than 5 mm from the CS (minimum distance 1 ± 0.4 mm) over a mean length of 16 ± 9 mm in patients with right-dominant coronary circulation and over a mean length of 86 ± 11 mm in patients with left-dominant coronary circulation. Conclusion The CS often lies very close to the esophagus and coronary arteries. During radiofrequency energy ablation in the CS, caution should be exercised to prevent injury to surrounding structures.

Background— An anatomic approach of left atrial radiofrequency circumferential ablation (LACA) to encircle the pulmonary veins is often effective in eliminating paroxysmal atrial fibrillation (AF). However, no electrophysiological end points other than voltage abatement and/or conduction slowing or block across ablation lines have been used. It has been unclear whether noninducibility of AF is a clinically useful end point. Methods and Results— In 100 patients with paroxysmal AF (mean age, 55±10 years), LACA to encircle the left- and right-sided pulmonary veins was performed during AF, with additional ablation lines in the posterior left atrium and mitral isthmus, with an 8-mm-tip catheter. After completion of this lesion set, sinus rhythm was present, and AF lasting >60 seconds was not inducible in 40 patients (40%; group 1). The 60 patients in whom AF was still present or who still had inducible AF were randomly assigned to no further ablation (group 2; 30 patients) or to additional ablation lines along the left atrial septum, roof, and/or anterior wall where there were fractionated electrograms (group 3; 30 patients). In group 3, AF was rendered noninducible in 27 of 30 patients (90%). At a 6-month follow-up, 67% of patients in group 2 were free of AF without drug therapy compared with 86% of patients in group 3. ( P =0.05, log-rank test). Left atrial flutter occurred in 17% and 27% of patients in each group, respectively ( P =0.3). Conclusions— After LACA in patients with paroxysmal AF, AF usually can be rendered noninducible by additional ablation at sites of fractionated electrograms. Noninducibility of AF attained by additional electrogram-guided left atrial ablation may be associated with a better midterm clinical outcome than when AF is still inducible after LACA alone.

ObjectivesWe sought to determine whether elimination of pulmonary vein (PV) arrhythmogenicity is necessary for the efficacy of left atrial circumferential ablation (LACA) for atrial fibrillation (AF).BackgroundThe PVs often provide triggers or drivers of AF. It has been shown that LACA is more effective than PV isolation in eliminating paroxysmal AF. However, it is not clear whether complete PV isolation is necessary for the efficacy of LACA.MethodsIn 60 consecutive patients with paroxysmal (n = 39) or chronic (n = 21) AF (mean age 53 ± 12 years), LACA to encircle the left- and right-sided PVs, with additional lines in the posterior left atrium and along the mitral isthmus, was performed under the guidance of an electroanatomic navigation system. The PVs were mapped with a decapolar ring catheter before and after LACA. If PV isolation was incomplete, no attempts at complete isolation were made.ResultsAfter LACA, there was incomplete electrical isolation of one or more PVs in 48 (80%) of the 60 patients. The prevalence of PV tachycardias was 82% before and 8% after LACA (p < 0.001). At 11 ± 1 months of follow-up, 10 (83%) of the 12 patients with complete and 39 (81%) of 48 patients with incomplete PV isolation were free from recurrent AF without antiarrhythmic drug therapy (p = 1.0). A successful outcome was not related to the number of completely isolated PVs per patient (p = 0.6).ConclusionsLeft atrial circumferential ablation modifies the arrhythmogenic substrate within the PVs. Complete electrical isolation of the PVs is not a requirement for a successful outcome after LACA.

Pulmonary Vein Impedance. Introduction: During radiofrequency ablation to encircle or isolate the pulmonary veins (PVs), applications of radiofrequency energy within a PV may result in stenosis.The aim of this study was to determine whether monitoring of real-time impedance facilitates detection of inadvertent catheter movement into a PV. Methods and Results: In 30 consecutive patients (mean age 53 ± 11 years) who underwent a left atrial ablation procedure, the three-dimensional geometry of the left atrium, the PVs, and their ostia were reconstructed using an electroanatomic mapping system.The PV ostia were identified based on venography, changes in electrogram morphology, and manual and fluoroscopic feedback as the catheter was withdrawn from the PV into the left atrium.Real-time impedance was measured at the ostium, inside the PV at approximately 1 and 3 cm from the ostium, in the left atrial appendage, and at the posterior left atrial wall. There was an impedance gradient from the distal PV (127 ± 30 � ) to the proximal PV (108 ± 15 � )t o the ostium (98 ± 11 � )i n each PV (P< 0.01). There was no significant impedance difference between the ostial and left atrial sites.During applications of radiofrequency energy, movement of the ablation catheter into a PV was accurately detected in 80% of the cases (20) when there was an abrupt increase of ≥4 � in real-time impedance. Conclusion: There is a significant impedance gradient from the distal PV to the left atrium.Continuous monitoring of the real-time impedance facilitates detection of inadvertent catheter movement into a PV during applications of radiofrequency energy. (J Cardiovasc Electrophysiol, Vol. 15, pp. 674-678, June 2004)

The purpose of this study was to determine the effect of left atrial circumferential ablation on the size of the left atrium and pulmonary veins (PVs).The long-term effects of left atrial circumferential ablation on left atrial and PV size and anatomy have not been analyzed in quantitative fashion.PV and left atrial sizes were analyzed in 41 consecutive patients (mean age 54 +/- 12 years) with paroxysmal (n = 25) or chronic (n = 16) atrial fibrillation. Computed tomography of the chest with three-dimensional reconstruction was performed before and 4 +/- 2 months after left atrial circumferential ablation. Left atrial circumferential ablation was performed to encircle the PVs 1 to 2 cm from the ostia, using a power output of 70 W. Additional ablation lines were created in the posterior left atrium and mitral isthmus. Radiofrequency energy also was delivered within the circles and at the PV ostia in 51% of patients at a reduced power output of 35 W.At 6 months, 36 patients (88%) were in sinus rhythm without antiarrhythmic drug therapy, including 3 patients (7%) who developed persistent left atrial flutter and underwent subsequent successful ablation of atrial flutter. There was a 15 +/- 16% decrease in left atrial volume (P.01) and 10 +/- 35% decrease in PV ostial area (P.01), without focal narrowing, in patients with a successful outcome. Focal PV stenosis did not occur in any of the 41 patients.Maintenance of sinus rhythm after left atrial circumferential ablation is associated with reduced left atrial and PV ostial size. Left atrial circumferential ablation for atrial fibrillation does not cause PV stenosis.

Objectives The aim of this study was to determine the mechanisms responsible for recurrent atrial fibrillation (AF) after pulmonary vein isolation (PV) by segmental ostial ablation. Background Recovery of conduction into a previously isolated PV is a common observation when there is recurrent AF soon after segmental ostial ablation. However, the mechanisms of recurrent AF have been unclear. Methods A repeat ablation procedure was performed in 50 patients who had recurrent paroxysmal AF at a mean of 7 ± 6 months after segmental ostial ablation to isolate the PVs. During the repeat procedure, a ring catheter was inserted into each PV during sinus rhythm and AF to determine whether the veins were still isolated and, if not, whether there were PV tachycardias with a cycle length shorter than in the adjacent left atrium during AF. Results There was recovery of conduction over a previously ablated muscle fascicle in ≥1 PV in 49 patients (98%). There were 10 ± 2 episodes of PV tachycardia per minute in 36 (72%) of the 50 patients during AF. Repeat ablation was performed by segmental ostial ablation (23 patients) or by left atrial catheter ablation to encircle the left- and right-sided PVs 1 to 2 cm from the ostia, with additional ablation lines in the posterior left atrium and mitral isthmus (27 patients). At 6-month follow-up, among 23 patients who underwent repeat ablation by segmental ostial ablation, AF recurred in 4 (21%) of the 19 patients who had PV tachycardias and in 3 (75%) of the 4 patients who did not ( P = .03). Among the 27 patients who underwent left atrial ablation, AF recurred in 2 (12%) of the 17 patients who had PV tachycardias and in 1 (10%) of the 10 patients who did not ( P = 0.7). Conclusions Recovery of conduction in previously ablated muscle fascicles is a common finding in patients with recurrent AF after segmental ostial ablation. The efficacy of repeat segmental ostial ablation depends on the presence of PV tachycardias, whereas left atrial ablation is effective regardless of whether PV tachycardias are present or not during AF.

A hand-carried personal ultrasound device (HCPUD) may be used for rapid cardiac screening by physicians with limited echo training. Our objective was to determine the accuracy of rapid HCPUD evaluation of left ventricular (LV) size and function when used by a Cardiology Fellow. Forty-five patients underwent an HCPUD exam using a 2.4-kg device with a 2- to 4-MHz curved transducer and color power Doppler (SonoSite). The results were compared with sonographer-performed and echocardiographer-interpreted exams using conventional equipment. The HCPUD exam lasted 6 ± 2 minutes. There was 100% agreement between HCPUD and conventional echo on qualitative assessment of LV systolic function. Comparing the HCPUD and conventional linear measurements of left ventricular end-diastolic dimension (LVEDD) and of interventricular septal (IVS) thickness: LVEDD is HCPUD = 0.94 conventional −0.2,r = 0.82, P < 0.0001; IVS is HCPUD= 0.59conventional+0.6, r = 0.69, P < 0.0001. Thus, an HCPUD can effectively be used after limited training to rapidly screen for qualitative abnormalities of LV systolic function. Quantitative measurements of smaller structures with the HCPUD are more challenging. (ECHOCARDIOGRAPHY, Volume 20, May 2003)

SESSION 32: CATHETER ABLATION V: New Techniques and Approaches Friday, May 6, 2005 10:45 a.m.–12:15 p.m.

Asymptomatic Atrial Fibrillation. Introduction: The long-term efficacy of radiofrequency catheter ablation of atrial fibrillation (AF) has been based on patient-reported symptoms suggestive of AF. However, asymptomatic recurrences of AF may remain undetected. The aim of this study was to determine the prevalence of asymptomatic recurrences of AF after an apparently successful catheter ablation procedure for AF. Methods and Results: Among 244 consecutive patients (mean age 53 ± 11 years) who underwent a pulmonary vein isolation procedure for symptomatic paroxysmal AF and who reported no symptoms of recurrent AF at ≥6 months after the procedure, 60 patients with a history of ≥1 episode of AF per week were asked to participate in this study. Preablation, these patients had experienced 19 ± 13 episodes of AF per month. The patients were provided with a patient-activated transtelephonic event recorder for 30 days, a mean of 642 ± 195 days after the ablation procedure, and were asked to record and transmit recordings on a daily basis and whenever they felt palpitations. Seven patients (12%) felt palpitations during the study, although they had not experienced symptoms previously. Each of these 7 patients had an episode of AF documented with the event monitor during symptoms. In these 7 patients, the mean number of episodes per month decreased from 19 ± 14 preablation to 3 ± 1 postablation (P < 0.001). Among the 53 asymptomatic patients, an episode of AF was captured in 1 (2%) patient during the study period. Conclusion: Asymptomatic recurrences of AF after an apparently successful catheter ablation procedure for symptomatic paroxysmal AF are infrequent. (J Cardiovasc Electrophysiol, Vol. 15, pp. 920-924, August 2004)

Objectives The purpose of this study was to identify ventricular tachycardia (VT) isthmus sites by pace-mapping within scar tissue and to identify electrogram characteristics that are helpful in identifying VT isthmus sites during sinus rhythm (SR). Background Pace-mapping has been used in the scar border zone to identify the exit site of post-infarction VT. Methods In 19 consecutive patients (18 men, mean age 66 ± 9 years, mean ejection fraction 0.24 ± 0.12) with post-infarction VT, a left ventricular voltage map was generated during SR. Pace-mapping was performed at sites with abnormal electrograms or isolated potentials. Radiofrequency ablation was performed at isthmus sites as defined by pace-mapping (perfect pace-map = 12/12 matching electrocardiogram leads; good pace-map = 10/12 to 11/12 matching electrocardiogram leads) and/or entrainment mapping. Results A total of 81 VTs (mean cycle length 396 ± 124 ms) were inducible. In 16 of the 19 patients, a total of 41 distinct isthmus areas of 41 distinct VTs were identified and successfully ablated. All but one displayed isolated potentials during SR. Furthermore, 22 of the 81 VTs (27%) for which no isthmus was identified became noninducible after ablation of a targeted VT. The 16 patients in whom ≥1 isthmus was identified and ablated were free of arrhythmic events during a mean follow-up of 10 months. Conclusions During SR, excellent or good pace-maps at sites of isolated potentials within areas of scar identify areas of fixed block that are protected and part of the critical isthmus of post-infarction VT. Shared common pathways might explain why non-targeted VTs might become noninducible after ablation of other VTs.

Objectives The aim of this study was to determine the effects of circumferential pulmonary vein ablation (CPVA) and electrogram-guided ablation (EGA) on the spectral characteristics of atrial fibrillation (AF) and the relationship between changes in dominant frequency (DF) and clinical outcome. Background Circumferential pulmonary vein ablation and EGA have been used to eliminate AF. Spectral analysis may identify high-frequency sources. Methods In 84 consecutive patients, CPVA (n = 42) or EGA (n = 42) was performed for paroxysmal (n = 49) or persistent (n = 35) AF. During EGA, complex electrograms were targeted. Lead V1and electrograms from the left atrium and coronary sinus were analyzed to determine the DF of AF before and after ablation. Results The left atrial DF was higher in persistent (5.83 ± 0.86 Hz) than paroxysmal AF (5.33 ± 0.76 Hz, p = 0.03). There was a frequency gradient from the left atrium to the coronary sinus (p = 0.02). Circumferential pulmonary vein ablation and EGA resulted in a similar decrease in DF (18 ± 17% vs. 17 ± 15%, p = 0.8). During a mean follow-up of 9 ± 6 months, the change in DF after CPVA was similar among patients with and without recurrent AF. An acute decrease in DF after EGA was associated with freedom from recurrent AF only in patients with persistent AF (19 ± 14% vs. 3 ± 6%, p = 0.02). Conclusions Both CPVA and EGA decrease the DF of AF, consistent with elimination of high-frequency sources. Whereas the efficacy of EGA is associated with a decrease in DF in patients with persistent AF, the efficacy of CPVA is independent of changes in DF. This suggests that CPVA and EGA eliminate different mechanisms in the genesis of persistent AF.