Anatomical characteristics of the cavotricuspid isthmus in patients with and without typical atrial flutter: Analysis with two- and three-dimensional intracardiac echocardiography

Introduction The cavotricuspid isthmus (CTI) is crucial in the ablation of typical atrial flutter (AFL), and consequently the CTI anatomy and/or its relation to resistant ablation cases have been widely described in human angiographic studies. Intracardiac echocardiography (ICE) has been shown to be a useful tool for determining detailed anatomical information. Thus, this technology may also allow the visualization of the anatomical characteristics of the CTI, providing an opportunity to further understand the anatomy. Aim We conducted a study to compare the anatomy of the CTI between the patients with and without AFL and to characterize the anatomy of the CTI in the patients with AFL resistant to ablation. Materials and methods Twelve patients with typical AFL and 20 without AFL were enrolled in the study. Two-dimensional (2D) intracardiac echocardiography (ICE) was performed. The recordings were obtained with a 9F, 9-MHz ICE catheter from the right ventricular outflow tract to the inferior vena cava by pulling the catheter back 0.3 mm at a time under guidance with echocardiographic imaging in a respiration-gated manner. Three-dimensional (3D) reconstruction of the images of the CTI were made with a 3D reconstruction system. After the acquisition of the ICE, the CTI ablation was performed in the patients with AFL. Results The 2D and 3D images provided clear visualization of the tricuspid valve, coronary sinus ostium, fossa ovalis and Eustachian valve/ridge (EVR). The CTI was significantly longer in the patients with AFL than in those without AFL (median length 24.6 mm (range 17.0–39.1 mm) versus median length 20.6 mm (range 12.5–28.0 mm), respectively, P < 0.05). However, a deep recess due to a prominent EVR was observed in 9 of 12 (75%) patients with AFL and in 12 of 20 (60%) patients without AFL (N.S.). A deep recess and the relatively long CTI were related to aging in all the study patients, and that relationship was similar in a limited number of patients without AFL. In five patients with AFL resistant to ablation, a deep recess and prominent EVR were observed. Conclusions The 2D and 3D ICE were useful for visualizing the complex anatomy of the CTI and identifying the anatomical characteristics of the CTIs refractory to ablation therapy. The anatomical changes observed in the CTI region may simply be the result of aging and may partially be involved in the development of AFL.     

Acute success and short-term follow-up of catheter ablation of isthmus-dependent atrial flutter; a comparison of 8 mm tip radiofrequency and cryothermy catheters

Objectives To compare the acute success and short-term follow-up of ablation of atrial flutter using 8 mm tip radiofrequency (RF) and cryocatheters. Methods Sixty-two patients with atrial flutter were randomized to RF or cryocatheter (cryo) ablation. Right atrial angiography was performed to assess the isthmus. End point was bidirectional isthmus block on multiple criteria. A pain score was used and the analgesics were recorded. Patients were followed for at least 3 months. Results The acute success rate for RF was 83% vs 69% for cryo (NS). Procedure times were similar (mean 144 ± 48 min for RF, vs 158 ± 49 min for cryo). More applications were given with RF than with cryo (26 ± 17 vs. 18 ± 10, p < 0.05). Fluoroscopy time was longer with RF (29 ± 15 vs. 19 ± 12 min, p < 0.02). Peak CK, CK-MB and CK-MB mass were higher, also after 24 h in the cryo group. Troponin T did not differ. Repeated transient block during application (usually with cryoablation) seemed to predict failure. Cryothermy required significantly less analgesia (p < 0.01), and no use of long sheaths (p < 0.005). The isthmus tended to be longer in the failed procedures (p = 0.117). This was similar for both groups, as was the distribution of anatomic variations. Recurrences and complaints in the successful patients were similar for both groups, with a very low recurrence of atrial flutter after initial success. Conclusions In this randomized study there was no statistical difference but a trend to less favorable outcome with 8 mm tip cryocatheters compared to RF catheters for atrial flutter ablation. Cryoablation was associated with less discomfort, fewer applications, shorter fluoroscopy times and similar procedure times. The recurrence rate was very low. Cryotherapy can be considered for atrial flutter ablation under certain circumstances especially when it has been used previously in the same patient, such as in an AF ablation.     

Clinical outcome of left atrial ablation for paroxysmal atrial fibrillation is related to the extent of radiofrequency ablation

Background  The exact mechanism of eliminating atrial fibrillation (AF) by catheter ablation techniques is not known. We investigated whether the extent of atrial damage conferred by radiofrequency lesions is a predictor of success after ablation, regardless of the method employed for ablation. Methods  Ninety consecutive patients with paroxysmal AF subjected to ostial–antral pulmonary vein isolation (n = 41) or circumferential (n = 49) catheter ablation were studied. Results  At 1 year follow-up, 16 out of 41 patients (39%) with ostial–antral ablation and 16 out of 49 patients (32.6%) with circumferential ablation had AF recurrences (p = 0.5). The mean duration of radiofrequency ablation lesions was statistically significantly shorter in patients with recurrence of AF compared to those with sinus rhythm 1 year after ablation (22.3 ± 4.2 min vs. 27.2 ± 4.5 min, respectively, p value < 0.001). Radiofrequency ablation time was inversely associated with the risk of recurrence of AF 1 year after ablation and this relationship remained even after adjustment for potential confounding factors such as age, sex, left atrial size, and type of ablation technique (ostial–antral or circumferential; HR  =  0.80, 95% CI: 0.72–0.87, p < 0.001). Conclusions  Duration of radiofrequency energy delivery is an independent predictor of clinical outcome at 1 year follow-up both among patients undergoing circumferential as well as ostial–antral ablation.     

Impact of “hybrid therapy” on long-term rhythm control and arrhythmia related hospitalizations in patients with drug-refractory persistent and permanent atrial fibrillation

Background Recently, a “hybrid therapy” strategy has been used for successful rhythm control in persistent and permanent atrial fibrillation (AF) patients. The impact of this strategy on arrhythmia recurrences and subsequent AF related hospitalizations are unknown. Materials and Methods Forty-seven patients (66 ± 10 years) with symptomatic persistent (N = 26) or permanent (N = 21) AF underwent “hybrid therapy” and were followed for 24 ± 15 months. All patients underwent linear right atrial ablation and implantation of pacemaker or atrioventricular defibrillator (AVICD) capable of continuous right atrial pacing with previously ineffective antiarrhythmic drug therapy for AF prevention. Device data-logs were used to monitor AF recurrences. Results Freedom from permanent AF was 97, 90, and 83% at 6 months, 2 and 3 years, respectively. Sixteen patients (34%) had no recurrent AF after “hybrid therapy.” Thirty-one patients (66%) had a total of 55 AF recurrences (mean 1.8 per patient). There was a significant reduction in the mean AF related hospitalizations (from 3.5 ± 2.8 to 0.57 ± 1.1 per patient), cardioversion hospitalizations (from 3.5 ± 2.2 to 0.38 ± 0.5 per patient) and DC cardioversions (from 3.1 ± 3.9 to 0.7 ± 0.5 per patient) after hybrid therapy compared to event rates before therapy (p < 0.05 for all). Conclusions Rhythm control improves significantly with hybrid therapy in patients with persistent and permanent AF refractory to drugs and cardioversion therapy. This improvement is associated with a significant reduction in AF related hospitalizations and need for cardioversion therapy.     

Mechanism of recurrence after radiofrequency catheter ablation of atrial fibrillation guided by complex fractionated atrial electrograms

Background A better understanding of the mechanisms of recurrent atrial fibrillation (AF) after radiofrequency ablation of complex, fractionated atrial electrograms (CFAEs) may be helpful for refining AF ablation strategies. Methods and results Electrogram-guided ablation (EGA) was repeated in 30 consecutive patients (mean age = 59 ± 8 years) for recurrent paroxysmal AF, 10 ± 4 months after the first ablation. During the first procedure, CFAEs were targeted without isolating all pulmonary veins (PVs). During repeat ablation, all PVs and the superior vena cava (SVC) were mapped with a circular catheter and the left atrium was mapped for CFAEs. EGA was performed until AF was rendered noninducible or all identified CFAEs were eliminated. During repeat ablation, ≥1 PV tachycardia was found in 83 PVs in 29 of the 30 patients (97%). Among these 83 PVs, 63 (76%) had not been completely isolated previously. During repeat ablation, drivers originating in a PV or PV antrum were identified only after infusion of isoproterenol (20 μg/min) in 12 patients (40%). At 9 ± 4 months of follow-up after the repeat ablation procedure, 21 of the 30 patients (70%) were free from recurrent AF and flutter without antiarrhythmic drugs. Conclusions Recurrence of AF after EGA is usually due to PV tachycardias. Therefore, it may be preferable to systematically map and isolate all PVs during the first procedure. High-dose isoproterenol may be helpful to identify AF drivers.     

Assessment of the maximum voltage-guided technique for cavotricuspid isthmus ablation during ongoing atrial flutter

Objectives We aimed to test the maximum voltage-guided cavotricuspid isthmus (CTI) ablation technique during ongoing atrial flutter. Background Former pathological and electrophysiological studies clarified that the cavotricuspid isthmus is composed of distinct muscular bundles, which are responsible for the conduction of electrical activation. Based on this observation, a maximum voltage-guided ablation technique (MVGT) was developed. This technique was assessed during pacing from the coronary sinus and was reported to be a feasible method to reach bidirectional isthmus block without the need for a complete anatomic ablation line. Methods This was a prospective, randomized single center study. Twenty patients underwent CTI ablation during atrial flutter. In group I (10 pts) CTI ablation was performed with complete anatomical ablation line. In group II (10 pts) ablation was guided by the highest amplitude potentials on the CTI sequentially until bidirectional isthmus block was reached. The following parameters were compared: acute success rate, procedure time, fluoroscopy time, number of radiofrequency (RF) applications and total RF duration. Results In all patients, atrial flutter terminated during ablation. Bidirectional isthmus block could be achieved in all pts. Procedure time was shorter in group II (107 ± 40 vs 68 ± 19 min, p < 0.01). Significantly less fluoroscopy was used in group II (22.6 ± 10.6 vs 12.1 ± 3.8 min, p < 0.01). There were less RF applications in group II (27.1 ± 21.5 vs 5.9 ± 2.4, p < 0.001). Conclusions (1) The major finding of this study is that MVGT is a feasible method even during ongoing atrial flutter. (2) Our data confirm that MVGT is an effective technique for CTI ablation with considerable decrease in procedure and fluoroscopy times.     

Ablation of Atrial Fibrillation at the Time of Cavotricuspid Isthmus Ablation in Patients With Atrial Flutter Without Documented Atrial Fibrillation Derives a Better Long‐Term Benefit

AF Ablation in Patients With Only Documentation of Atrial Flutter. Objectives: The aim of the study was to evaluate whether isolation of the pulmonary veins (PVs) at the time of cavotricuspid isthmus (CTI) ablation is beneficial in patients with lone atrial flutter (AFL). Background: A high proportion of patients with lone persistent AFL have recurrent episodes of atrial fibrillation (AF) after CTI ablation. However, the benefit of AF ablation in patients with only documentation of AFL has not been determined. Methods: Forty‐eight patients with typical lone persistent AFL (age 56 ± 6; 90% male) were randomized to CTI ablation (Group A; n = 25) or to CTI + PV isolation (PVI) (Group B; n = 23). In addition to PVI, some patients in group B underwent ablation of complex fractionated electrograms and/or creation of left atrial roof and mitral isthmus ablation line in a stepwise approach when AF was induced and sustained for more than 2 minutes. Mean follow‐up was 16 ± 4 months with a 48‐hour ambulatory monitor every 2 months. Results: There were no recurrences of AFL in either group. Six patients in group B (22%) underwent a stepwise ablation protocol. AF organized and terminated in 5 patients during ablation (83%). Complication rate was not significantly different among the groups. Twenty patients in group B (87%) and 11 patients in group A (44%) were free of arrhythmias on no medications at the end of follow‐up (P < 0.05). Conclusions: Ablation of AF at the time of CTI ablation results in a significantly better long‐term freedom from arrhythmias. (J Cardiovasc Electrophysiol, Vol. 22, pp. 34‐38, January 2011)     

Efficacy and safety of dofetilide in patients with atrial fibrillation and atrial flutter

Background  Dofetilide, an I_Kr blocker has been demonstrated to be effective in terminating persistent atrial fibrillation and flutter (AF/AFL), and in maintaining sinus rhythm after direct current cardioversion (CV). It is not known, however, whether pharmacological conversion with dofetilide predicts maintenance of sinus rhythm. In addition, there is limited information comparing the efficacy of dofetilide in persistent versus paroxysmal AF/AFL. Methods and Results  Eighty consecutive patients with AF/AFL (51 persistent, 29 paroxysmal) admitted for initiation of dofetilide were studied. Termination of persistent AF/AFL occurred in 61% of patients while 39% required CV. After 21 ± 19 months of follow-up, 37% of patients with persistent AF/AFL were free of recurrence. Acute conversion with dofetilide did not predict long term efficacy. Dofetilide was more effective in maintaining sinus rhythm in patients with AFL (65%) than in those with AF (25%) (p < 0.05). Dofetilide was more likely to maintain sinus rhythm in patients with persistent than paroxysmal AF/AFL (37 vs. 14%; p < 0.05). Torsades de Pointes developed in two patients despite careful dosing and monitoring of QT changes. Conclusions  Dofetilide is more effective in patients with persistent than in those with paroxysmal AF/AFL. Importantly, short-term response does not necessarily predict long-term efficacy. Significant proarrhythmia can occur even with careful in-hospital monitoring. Dr. Banchs and Dr. Wolbrette contributed equally to this study. Presented in abstract form at the XIII World Congress on Cardiac Pacing and Electrophysiology; December 3, 2007; Rome and published in abstract form (Giornale Italiano di Aritmologia e Cardiostimolazione 2007;10(3):26).     

Catheter ablation of atrial fibrillation in patients with hyperthyroidism

Aims To study the clinical efficacy of catheter ablation for treating patients with hyperthyroidism-related atrial fibrillation (AF). Materials and methods The study involved 16 patients (12 males; age, 59.8 ± 11.3 years) with hyperthyroidism-related AF, who had all been euthyroid for more than 3 months but still suffered from highly symptomatic and antiarrhythmia drug (AAD)-refractory AF. Circumferential pulmonary vein ablation (CPVA) guided by a 3-D mapping system was carried out to encircle the ipsilateral pulmonary veins (PVs) with a procedural endpoint of continuity of the circular lesions and PV isolation. Success was defined as the absence of any atrial tachyarrhythmia (ATa) off AADs beyond the first 3 months after the procedure. Results CPVA was safely carried out in each of the 16 patients without any complications. PV isolation was achieved in all the treated PVs. After a mean follow-up of 15.8 ± 11.8 (range, 6–55) months, 9 patients (56%) were free of ATa without any AADs beyond the first 3 months. AF relapsed in the remaining 7 patients, among whom 4 responded to AAD therapy and 3 were totally unresponsive. Conclusion For patients suffering hyperthyroidism-related AF, CPVA guided by a 3-D mapping system could represent one of the therapeutic options. Drs. Chang Sheng Ma and Xu Liu are co-first authors for this paper.     

A prospective randomised comparison of large-tip cryoablation and 8-mm-tip radiofrequency catheter ablation of atrial flutter

Purpose  Although radiofrequency (RF) energy is routinely used for tricuspid isthmus (TI) ablation, it is often associated with discomfort. The paucity of studies comparing the feasibility and efficacy of cryo- versus RF energy for TI-ablation urged us to conduct a prospective, randomised trial. Methods  Forty patients with atrial flutter (AFl) were randomised to RF- or cryoenergy for TI-ablation. Perceived pain was scored from 1 to 10 on a Visual Analogue Scale. Results  Significantly lower pain scores were recorded for cryoablation versus RF ablation (0.96 ± 0.73 versus 4.2 ± 2.4, p = 0.00004). Cryoablation was associated with significantly longer procedure duration and ablation time (137 ± 35 versus 111 ± 29 min, p = 0.016 and 81 ± 40 versus 48 ± 30 min, p = 0.007) and lower acute success rate (56% versus 100%, p = 0.001) than RF ablation. The recurrence of AFl was 20% (cryo) versus 15% (RF; p = 0.45) after a mean of 15.1 months follow-up. Conclusion  Cryoablation results in significantly less pain and discomfort compared to RF ablation of AFl, which is offset by the significantly lower acute success rate.     

Single cryothermia applications of less than five minutes produce permanent cavotricuspid isthmus block in humans

OBJECTIVES: The aim of this study was to compare single-3-minute (single-3) with double-3-minute (double-3) cryothermia applications for treatment of atrial flutter (AFL). BACKGROUND: Previous animal studies have indicated the need for a double 5-minute cryothermal application to create large and permanent lesions. METHODS: Forty patients (56 +/- 13 years old) with typical AFL (cycle length 229 +/- 35 ms) were randomized to single-3 (n = 20) or double-3 (n = 20) cryothermia applications at each site along the cavotricuspid isthmus (CTI). Cryoablation was performed with the CryoCor cryoablation system. A successful procedure was defined as noninducibility of AFL with the concomitant presence of bidirectional CTI conduction block under isoproterenol infusion. RESULTS: All but 1 patient (95%) of the single-3 group and all patients (100%) of the double-3 group were successfully ablated. The number of sites needed to create isthmus conduction block was 9 +/- 4 (single-3) and 8 +/- 2 (double-3) (NS). Fluoroscopy time did not differ between the two groups (single-3: 31 +/- 14; double-3: 36 +/- 17 min, NS). The procedure time of the single-3 group was significantly shorter compared to the procedure time of the double-3 group (mean procedure duration 132 +/- 64 vs 159 +/- 50 min, P < .04). After a mean follow-up of 11.7 +/- 4.7 months, two recurrences of AFL occurred in the double-3 group. CONCLUSIONS: Single cryothermia applications of 3 minutes produce permanent CTI conduction block in patients with typical AFL and significantly reduce procedure duration.     

Safety and efficacy of catheter ablation of atrial fibrillation in patients with diabetes mellitus—single center experience

Background and objective Little is known about the outcome of catheter ablation of atrial fibrillation (AF) in patients with diabetes mellitus (DM). We investigated the safety and efficacy of catheter ablation of AF in patients with DM. Materials and methods Thirty one patients with DM from a group of 263 consecutive patients undergoing a first-time catheter ablation of AF procedure were enrolled in a prospective study. The ablation protocol (guided by CARTO system) consisted in two continuous circular lesions around ipsilateral pulmonary veins. Results The following clinical characteristics differed between DM and no-DM patients: age (62.0 ± 10.8 vs. 56.1 ± 10.6 years, P = 0.004), longer AF history (9.6 ± 9.3 vs. 6.7 ± 6.3 years, P = 0.024), significantly larger left atrium size (41.1 ± 7.8 vs. 38.3 ± 5.8 mm, P = 0.021), hypertension (58.1 vs. 35.8%, P = 0.018) and structural heart disease (67.7 vs. 43.5%, P = 0.011). Despite a similar AF recurrence rate in DM and no-DM patients (32.3 vs. 22.4%, P = 0.240), the ablation procedure was complicated in 28 patients (11 hematomas, three cardiac tamponades and three strokes) and the incidence of complications was significantly higher in DM than in no-DM patients (29.0 vs. 8.2%, respectively, P = 0.002). Multivariate analysis showed that DM was an independent risk factor for complications occurrence (odd ratio 5.936, 95% confidence interval 2.059 to 17.112, P = 0.001). Conclusions First catheter ablation of AF procedure in DM patients was equally efficacious than in no-DM patients. However, DM patients had a higher incidence of complications, mostly thrombotic or hemorrhagic.     

Higher Rate of Recurrent Atrial Flutter and Atrial Fibrillation Following Atrial Flutter Ablation After Cardiac Surgery

Atrial Flutter After Cardiac Surgery . Introduction: Atrial flutter (AFL) is common after cardiac surgery. However, the types of post‐cardiac surgery AFL, its response to catheter‐based radiofrequency ablation, and its relationship to atrial fibrillation (AF) are unknown. Methods and Results: We retrospectively studied all patients who underwent mapping and ablation for AFL after cardiac surgery from January 1990 to July 2004. One hundred randomly selected patients without prior cardiac surgery (PCS) who underwent mapping and ablation of AFL served as the control population. A total of 236 patients formed the study population (mean age 62 + 13 years, 22% female) and 100 patients formed the control population (mean age 60 + 13 years, 25% female). The majority of patients without PCS had cavo‐tricuspid isthmus (CTI)‐dependent AFL when compared to patients with PCS (93% vs 72%, respectively, P < 0.0001). In contrast, scar‐related AFL was more common in patients with PCS as compared to patients without PCS (22% vs 3%, P < 0.0001). Predictors of scar related AFL in multivariable regression analysis included PCS and left‐sided AFL. Acute success rates and complications were similar between the groups. When compared to patients with AFL ablation without PCS, those that had AFL after PCS had higher rates of recurrence of both AFL (1% vs 12%, P < 0.0001; mean time to recurrence 1.85 years) and AF (16% vs 28%, P = 0.02; mean time to recurrence 2.67 years). Conclusion: Despite ablation of AFL, patients with PCS have a higher rate of AFL and AF when compared to patients without PCS who underwent ablation of atrial flutter during long‐term follow‐up. (J Cardiovasc Electrophysiol, Vol. pp. 760‐765, July 2010)     

Atypical Electrocardiographic Features of Cavotricuspid Isthmus‐Dependent Atrial Flutter Occurring during Left Atrial Fibrillation Ablation

Background: Patients who have undergone percutaneous catheter ablation for atrial fibrillation (AF) may develop cavotricuspid isthmus (CTI)‐dependent atrial flutter (AFL), which can occur either spontaneously during left atrial (LA) ablation for AF or by induction from sinus rhythm during the procedure. The electrocardiographic (ECG) characteristics of CTI‐dependent AFL occurring during LA ablation have not been described. The purpose of this study was to describe the ECG features of CTI‐dependent AFL occurring during percutaneous LA catheter ablation for AF. Methods and Results: Of 223 patients presenting for first AF ablation at our institution between May 2004 and February 2008, 20 patients (9%) developed CTI‐dependent AFL during LA ablation for AF. CTI‐dependent AFL developed spontaneously in 4 patients (20%) and was induced in 16 patients (80%). Among these 20 patients, 3 (15%) had typical ECG patterns and 17 (85%) had atypical ECG patterns. Flutter waves in the inferior leads were biphasic in 10 patients (50%), downward in 3 patients (15%), positive in 3 patients (15%), and not fitting the above classifications in 4 patients (20%). There was no statistically significant association between AFL pattern and LA size, left ventricular ejection fraction, total ablation time, duration of prior AF, or type of prior AF. Conclusion: A majority of patients with CTI‐dependent AFL occurring during LA ablation have atypical ECG patterns. Biphasic flutter waves in the inferior leads are common ECG features, occurring in one‐half of patients. Right atrial CTI‐dependent AFL should be suspected even if the ECG appearance is atypical. Ann Noninvasive Electrocardiol 2010;15(3):200–208     

Is there an evidence of pulmonary vein stenosis following epicardial microwave ablation of atrial fibrillation?

Background  Surgical ablation techniques using microwave energy are an alternative to catheter based ablation therapy in the treatment of atrial fibrillation (AF). However, little is known about potential procedure-related complications. We investigate, whether there is evidence of pulmonary vein stenosis (PVST) in patients with atrial fibrillation undergoing epicardial microwave ablation. Methods  14 patients (ten males and four females) with AF and structural heart disease underwent cardiac surgery for the underlying disease and concomitant ablation of AF using microwave energy. In these patients with a mean age of 71 ± 8 years microwave energy was applied epicardially on the beating heart. Ablation was implemented using a flexible microwave tool with a 40 mm long tip to create isolation of the pulmonary veins. Each application was performed with 65 watt for 90 s. Follow-up was performed twice at a mean of 207 ± 73 days and 395 ± 102 days. Patients were evaluated by 12-lead-ECG and echocardiography. Multidetector helical computer tomographic (MDCT) imaging was done in seven patients to show morphology of the pulmonary veins. Results  On second follow-up 11 patients were seen. ECG showed sinus rhythm in six patients (55 %) and atrial fibrillation in five patients (45%). MDCT showed a moderate pulmonary vein stenosis (50–70%) in one patient. The patient did not suffer from palpitations, dyspnea, angina or syncope. Conclusions  Epicardial microwave ablation is an accepted treatment of atrial fibrillation. The procedure can be done off-pump on the beating heart. Nevertheless, pulmonary vein stenosis is a possible complication of this procedure, which should be kept in mind and evaluated during the follow-up.     

Pulmonary vein encircling ablation alters the atrial electrophysiologic response to autonomic stimulation

Objective Pulmonary vein encircling ablation is often effective in the treatment of atrial fibrillation (AF). The success of the procedure does not depend upon creation of continuous lines of block. Thus mechanisms by which pulmonary vein encircling can cure AF remain unclear. Stimulation of cardiac autonomic ganglia alters atrial refractoriness and potentiates AF. We hypothesized that pulmonary vein encircling alters atrial autonomic function and that these alterations account in part for prevention of AF recurrences following ablation. Methods Atrial effective refractory periods (ERP) and AF inducibility were quantified in ten dogs before and during central autonomic nerve stimulation. Pulmonary vein encircling ablation was then performed and electrophysiologic testing repeated. In two dogs subjected to sham procedures measurements were repeated without performance of ablation. Hearts were examined histologically. Results Autonomic nerve stimulation led to decreased atrial refractoriness and increased AF inducibility and duration. Each of these effects were attenuated following pulmonary vein encircling (e.g., mean ERP decreased before (−23.7 ± 1.8, p < 0.001) but not after ablation (−2.3 ± 1.9, p = 0.25); AF inducibility increased by 26% before vs. 5% after ablation). No attenuation was seen in the sham operated animals. Histologic analysis following pulmonary vein encircling demonstrated destruction of some but not all autonomic ganglia. Conclusion Autonomic stimulation shortens atrial refractory periods and potentiates AF. Pulmonary vein encircling ablation partially destroys atrial autonomic inputs, attenuates the refractory period shortening effect of autonomic stimulation and decreases AF inducibility. Destruction of autonomic ganglia may contribute to the anti-fibrillatory effects of pulmonary vein encircling and warrants further investigation. Potential conflict of interest: PSS is a consultant to and receives grant support from Biosense Webster Research Support. This study was supported by a research alliance with Medtronic Inc., Minneapolis, MN.     

典型心房扑动的经导管射频消融治疗

回顾分析 35例典型心房扑动 (简称房扑 )患者电生理检查和射频消融治疗的临床结果。心内激动标测显示沿三尖瓣环 (TA)逆钟向折返性房扑 2 7例 ,顺钟向折返 2例 ,同时存在二种折返 6例。 8例行TA峡部拖带起搏者均呈隐匿性拖带 ,起搏后间期与房扑周长差值为 1± 4(- 3～ 5 )ms。采用TA峡部双线性消融、后峡部或 /和间隔峡部消融的方法治疗所有患者均成功。 15例以房扑不能再诱发为手术终点 ,随访 10例 ,3例复发 ,复发率 30 % ;2 0例达到TA峡部双向阻滞 ,随访 19例 ,1例复发 ,复发率 5 % ,两组比较P <0 .0 5。随访的 2 9例中 ,7例发生心房颤动 (简称房颤 ) ,发生率 2 4%。与无房颤发作者相比 ,合并器质性心脏病、心房扩大和有房颤病史者的比例明显增加 (6 / 7比 9/ 2 2 ,6 / 7比 4/ 2 2和 7/ 7比 2 / 2 2 ,均P <0 .0 5 )。结果表明 ,心内激动标测结合拖带起搏技术可确定典型房扑的诊断 ,后峡部或间隔峡部消融是治疗房扑的有效方法 ,以TA峡部双向阻滞为手术终点较房扑不能被再诱发为终点可明显降低复发率。房扑消融术后发生房颤与合并器质性心脏病、心房扩大和术前存在房颤有关     

Accuracy of integration of multislice computed tomography imaging into three-dimensional electroanatomic mapping for real-time guided radiofrequency ablation of left atrial fibrillation—Influence of heart rhythm and radiofrequency lesions

Circumferential radiofrequency ablation around the orifices of the pulmonary veins is a curative catheter-based therapy of paroxysmal and persistent atrial fibrillation (AF). Three-dimensional cardiac image integration is a promising new technology to visualize the complex left atrial anatomy and neighbouring structures. This study aimed to validate the accuracy of integrating multislice computed tomography (MSCT) into three-dimensional electroanatomic mapping (EAM) to guide radiofrequency catheter ablation (CA) of AF. Forty consecutive patients (34 male, mean age 56 ± 10 years) with multidrug-resistant AF underwent 16-slice MSCT 1 day before radiofrequency CA. MSCT data were processed and imported to the Carto™ EAM system. Using the CartoMerge™ Image Integration Module, the generated EAM was aligned with the MSCT images. An integrated statistical algorithm provided information about the accuracy of the fusion process. In every single patient, MSCT images could be aligned with the EAM. Mean distance between the EAM points (n = 63 ± 14) and the MSCT surface was 1.6 ± 1.2 mm with no difference between sinus rhythm versus AF (p = 0.145) and no distinction between patients in paroxysmal versus persistent/permanent AF despite a significant difference in left atrial diameters. An average of 388 ± 81 radiofrequency ablation points were taken within the procedures resulting in a mean distance of 2.3 ± 1.8 mm between the EAM points and the MSCT image after the ablation procedure. There was a significant difference of alignment accuracy before and after radiofrequency CA (p < 0.001). MSCT images can be accurately integrated into three-dimensional EAM. Pre-interventional cardiac rhythm does not influence the precision of fusion. Accuracy of fusion deteriorates after radiofrequency CA.     

Reentry mechanisms and ablation of ECG-typical atrial flutters involving the cavo-tricuspid isthmus and the proximal coronary sinus

Aim

Reentry circuits of a rare typical atrial flutter (AFL) involving the cavo-tricuspid isthmus (CTI) and proximal coronary sinus (CS) are described based on electrophysiological data and effects of radiofrequency (RF).

Methods and results

Twelve patients with ECG-typical AFL in whom entrainment demonstrated that CTI and proximal CS were both part of the circuit were included. Initial RF target was CTI in 8 patients and proximal CS in 4. Success was defined as AFL termination/noninducibility. After CTI ablation, AFL cycle length (CL) increased in all: AFL persisted in 3, while in the other 5 AFL was interrupted but subsequently induced with the same morphology; before induction CTI bi-directional block was validated; success was obtained at the CS, targeting fragmented atrial potentials (APs). In those with first ablation at CS, AFL was interrupted in 3 with no AFL inducibility; in 1 AFL persisted with CL prolongation and was terminated at CTI. Two reentry patterns were identified: in 5 patients the inter-atrial septum as well as the mid-distal CS were outside of the circuit, while the CTI, proximal CS and Bachmann's bundle zone were inside, suggesting a left atrial component; in 1 patient electrophysiological mapping suggested an intra-CS circuit component. RF was successful in all without recurrence.

Conclusion

Electrophysiological mapping and RF effects suggest a continuum between the CTI and proximal CS in rare cases with ECG-typical AFL. RF inside the proximal CS, targeting fragmented APs, should be considered in any patient in whom CTI ablation failed to interrupt a typical AFL.     

Pulmonary vein isolation using transvenous catheter cryoablation for treatment of atrial fibrillation without risk of pulmonary vein stenosis

OBJECTIVES: We sought to evaluate the efficacy and safety of pulmonary vein (PV) isolation using transvenous cryoablation for the treatment of atrial fibrillation (AF). BACKGROUND: Although electrical isolation of PVs with radiofrequency energy for the treatment of AF is feasible, it is associated with a significant risk of PV stenosis. Cryoablation is a new alternative therapy allowing ablation of tissue while preserving its underlying architecture. METHODS: In 52 patients with paroxysmal (n = 45) or persistent (n = 7) AF, PV isolation using the CryoCor cryoablation system (CyroCor Inc., San Diego, California) with a 10F deflectable transvenous catheter was performed as guided by ostial PV potentials. Cryoablation was applied twice at each targeted site (2.5 to 5 min/application). Computed tomography (CT) of the thorax was performed at baseline and at 3 and 12 months to evaluate for PV stenosis. RESULTS: All targeted PVs were completely isolated in 49 (94%) of 52 of patients. Of 152 PVs targeted, 147 (97%) were successfully isolated (mean 3.0 PVs isolated per patient). After a mean period of 12.4 +/- 5.5 months of follow-up, 37 (71%) of 52 patients had no recurrence of AF or were clinically improved, including 29 patients (56%) who had no recurrence of AF with (n = 11) or without the use of anti-arrhythmic drugs. At 3 and 12 months, the CT scan showed no evidence of PV stenosis associated with cryoablation in any patients. CONCLUSIONS: Transvenous catheter cryoablation is an effective method to create PV electrical isolation for the treatment of AF. A clinically satisfactory result can be achieved in 71% of patients with AF, without the risk of PV stenosis.