Robotic magnetic navigation for atrial fibrillation ablation

OBJECTIVES

We assessed feasibility of magnetic catheter guidance in patients with atrial fibrillation (AF) undergoing circumferential pulmonary vein ablation (CPVA).

BACKGROUND

No data are available on feasibility of remote navigation for AF ablation.

METHODS

Forty patients underwent CPVA for symptomatic AF using the NIOBE II remote magnetic system (Stereotaxis Inc., St. Louis, Missouri). Ablation was performed with a 4-mm tip, magnetic catheter (65 degrees C, maximum 50 W, 15 s). The catheter tip was guided by a uniform magnetic field (0.08-T), and a motor drive (Cardiodrive unit, Stereotaxis Inc.). Left atrium maps were created using an integrated CARTO RMT system (Stereotaxis Inc.). End point of ablation was voltage abatement >90% of bipolar electrogram amplitude.

RESULTS

Remote ablation was successful in 38 of 40 patients without complications. The median mapping and ablation time was 152.5 min (range, 90 to 380 min) but was much longer in the first 12 patients (192.5 min vs. 148 min; p = 0.012). Median ablation time was 49.5 min (range, 17 to 154 min), but it was much shorter in the last 28 patients than in the first 12 patients (49 min vs. 70 min; p = 0.021). Patients receiving remote ablation had longer procedure times than control patients (p < 0.001) with similar mapping time but shorter ablation time on right-sided pulmonary veins. Many more mapping points regardless of their location were collected remotely (p < 0.001).

CONCLUSIONS

Remote magnetic navigation for AF ablation is safe and feasible with a short learning curve. Although all procedures were performed by a highly experienced operator, remote AF ablation can be performed even by less experienced operators.

Circumferential pulmonary-vein ablation for chronic atrial fibrillation

BACKGROUND

We conducted a randomized, controlled trial of circumferential pulmonary-vein ablation for the treatment of chronic atrial fibrillation.

METHODS

A total of 146 patients with a mean (+/-SD) age of 57+/-9 years who had chronic atrial fibrillation were randomly assigned to receive amiodarone and undergo two cardioversions during the first three months alone (the control group) or in combination with circumferential pulmonary-vein ablation. Cardiac rhythm was assessed with daily telephonic transmissions for one year. The left atrial diameter and the severity of symptoms were assessed at 12 months.

RESULTS

Among the 77 patients assigned to undergo circumferential pulmonary-vein ablation, ablation was repeated because of recurrent atrial fibrillation in 26 percent of patients and atypical atrial flutter in 6 percent. An intention-to-treat analysis showed that 74 percent of patients in the ablation group and 58 percent of those in the control group were free of recurrent atrial fibrillation or flutter without antiarrhythmic-drug therapy at one year (P=0.05). Among the 69 patients in the control group, 53 (77 percent) crossed over to undergo circumferential pulmonary-vein ablation for recurrent atrial fibrillation by one year and only 3 (4 percent) were in sinus rhythm without antiarrhythmic-drug therapy or ablation. There were significant decreases in the left atrial diameter (12+/-11 percent, P<0.001) and the symptom severity score (59+/-21 percent, P<0.001) among patients who remained in sinus rhythm after circumferential pulmonary-vein ablation. Except for atypical atrial flutter, there were no complications attributable to circumferential pulmonary-vein ablation.

CONCLUSIONS

Sinus rhythm can be maintained long term in the majority of patients with chronic atrial fibrillation by means of circumferential pulmonary-vein ablation independently of the effects of antiarrhythmic-drug therapy, cardioversion, or both. The maintenance of sinus rhythm is associated with a significant decrease in both the severity of symptoms and the left atrial diameter.

Endocardial impedance mapping during circumferential pulmonary vein ablation of atrial fibrillation differentiates between atrial and venous tissue

BACKGROUND

Circumferential pulmonary vein ablation (CPVA) is an effective treatment for atrial fibrillation (AF). Accurate left atrial (LA) mapping is essential for creating lesions at the LA-pulmonary vein (PV) junction, avoiding PV stenosis.

OBJECTIVES

The purpose of this study was to establish whether endocardial impedance varies within the LA and PVs and whether it is a useful tool for mapping and ablation.

METHODS

Pilot Phase: Three-dimensional LA maps were created using CARTO. Impedance (Z) was measured using a radiofrequency generator at multiple points in the LA, PV ostia (PVO), and deep PVs in 79 patients undergoing their first AF ablation (group 1) and 29 patients undergoing repeat CPVA (group 2). Prospective Phase: In an additional 20 patients, using pilot phase data, one operator defined catheter tip location as either LA or PVO based on CARTO and fluoroscopy. A second operator blinded to CARTO simultaneously did the same based on impedance at 15 +/- 4 points per patient.

RESULTS

Group 1: Z(LA) was 99.4 +/- 9.0 omega. Z(PVO) was higher (109.2 +/- 8.5 omega), rising further as the catheter advanced into deep PV (137 omega +/- 18). Z(PVO) differed from Z(LA) by 9 +/- 4 omega. Group 2 had a lower Z(LA) and Z(PVO) compared with group 1 (P <.05). Impedance monitoring differentiated between LA and PVO, with 91% specificity and sensitivity, 96% positive predictive value, and 81% negative predictive value. At 3-month follow-up, no patients had evidence of PV stenosis on magnetic resonance imaging.

CONCLUSION

Impedance mapping reliably identifies the LA-PV transitional zone, facilitating AF ablation, and its use is associated with a low incidence of PV stenosis.

Atrial fibrillation ablation: state of the art

Among several catheter-based strategies for curing atrial fibrillation (AF), 2 approaches have emerged as dominant strategies in current clinical practice: ostial segmental disconnection of all pulmonary veins (PVs) from the adjacent atrial tissue and circumferential PV ablation, first reported by our laboratory in Milan. The cure for AF by circumferential PV ablation has had a dramatic impact on morbidity, quality of life, and even mortality in patients with the most frequent cardiac arrhythmia. The last 10 years of AF ablation are characterized by a better understanding of AF mechanisms as well as by new and evolving concepts associated with innovation in technologies. We recently demonstrated, for the first time, the role of vagal denervation in enhancing long-term benefits from circumferential PV ablation. Unlike other strategies, our strategy was associated with high success rates in both paroxysmal and chronic AF. As a result, our initial approach did not substantially change over time, and now we have long-term results after >3 years of follow-up. Recently, we demonstrated the safety and feasibility of remote magnetic navigation of a soft magnetic-tip catheter within the left atrium, even at challenging sites for both mapping and ablation in patients with AF. Use of a robotic navigation system has begun a new era in interventional cardiac electrophysiology-without risk of major complications, such as cardiac tamponade or atrioesophageal fistula, even in less experienced laboratories.

Transcatheter radiofrequency ablation of atrial fibrillation in patients with mitral valve prostheses and enlarged atria

OBJECTIVES

Few data have been published on transcatheter ablation of atrial fibrillation (AF) in patients with mitral valve prostheses. Thus, we sought to report our experience.

BACKGROUND

Ablation is an effective treatment for AF. Patients with prosthetic mitral valves represent a special group because of an increased risk from the ablation procedure due to the possibility of damage to the prosthetic valve.

METHODS

Between July 2001 and July 2003, 26 patients with mitral valve prostheses (MVP) underwent circumferential pulmonary vein ablation for AF. A matched group of 52 ablated patients without MVP acted as control subjects. After a blanking period of three months, a follow-up of 12 months was considered for MVP patients and controls. Holter recordings were performed in all subjects at 3, 6, and 12 months.

RESULTS

Radiation exposure was higher in the MVP group, with fluoroscopy times of 35.3 +/- 21 min versus 20.9 +/- 15 min in controls. At the end of follow-up, 73% of MVP patients were in sinus rhythm, compared with 75% of controls. Atrial tachycardia occurred in six (23%) MVP patients, requiring repeat ablation in three, and one (2%) control subject, which settled without treatment. One transient ischemic attack and one femoral pseudoaneurysm occurred in the MVP group. No complications occurred in the control group.

CONCLUSIONS

Ablation of AF in patients with MVP is feasible, with outcomes similar to those of standard patients. Complications were higher among MVP patients with a greater radiation exposure and a higher incidence of post-ablation atrial tachycardia.

Atrial fibrillation ablation

Radiofrequency catheter ablation is currently used widely and successfully to treat a variety of arrhythmias, and ablation for atrial fibrillation represents the frontier of arrhythmia research. Development in many areas will offer to the electrophysiologic community a more rational and effective background upon which select patients for ablation and identify the optimal ablative strategy. Among mechanisms recognized for having a role in atrial fibrillation stay pulmonary vein focal triggers, rotor at the pulmonary vein-left atrial junction, a critical mass to sustain fibrillatory conduction and vagal ganglia. The latter represents the frontier of research as with new technologies based on magnetic resonance imaging they could be easily and specifically identified and targeted for ablation. It is fundamental that both CARTO and NavX systems are currently investigating integration with magnetic resonance imaging to reconstruct the left atrium. Furthermore a learning curve effect can be abated with the use of new systems for the remote control of the catheter such as stereotaxis. In the last decade, we empirically devised a technique that is both safe and effective for curing atrial fibrillation. Briefly, using a three-dimensional mapping system, either CARTO or NavX system, we reconstruct the left atrium and the pulmonary ostia; thereafter circumferential ablation lines are normally created starting at the lateral mitral annulus and withdrawing posterior then anterior to the left-sided pulmonary veins, passing between the left superior pulmonary vein and the left atrial appendage before completing the circumferential line on the posterior wall of the left atrium. The right pulmonary veins are isolated in a similar fashion, and then a posterior line connecting the two circumferential lines on the roof is performed to reduce the risk of macroreentrant atrial tachycardias. The endpoint for circumferential ablation is a > 70-90% reduction in voltage within the isolated regions. In this article we sought to describe critical methodological aspects of our techniques along with future implementation with new technologies and to summarize our published clinical experience on the most prestigious journals.

Prevention of Iatrogenic Atrial Tachycardia After Ablation of Atrial Fibrillation

Background— Circumferential pulmonary vein ablation (CPVA) is effective in curing atrial fibrillation (AF), but new-onset left atrial tachycardia (AT) is a potential complication. We evaluated whether a modified CPVA approach including additional ablation lines on posterior wall and the mitral isthmus would reduce the incidence of AT after PV ablation.

Methods and Results— A total of 560 patients (291 men, 52%; age, 56.5±7.3 years) entered the study; 280 were randomized to CPVA alone (group 1) and 280 to modified CPVA (group 2). The primary end point was freedom from AT after the procedure. In group 1, 28 patients (10%) experienced new-onset AT, and 41 (14.3%) experienced recurrent AF. In group 2, 11 patients (3.9%) experienced AT, and 36 (12.9%) had recurrent AF. Group 1 was more likely to experience AT than group 2 ( P =0.005). Freedom from AF after ablation was similar in both groups ( P =0.57). Among those in group 1, gap-related macroreentrant AT was documented in 23 of the 28 patients (82%), and focal AT was found in 5 (18%). In group 2, gap-related macroreentrant AT was found in 8 of the 11 patients (73%), and focal AT was seen in 3 (27%). Two patients in group 1 and 1 patient in group 2 had both AT and AF. The strongest predictor of AT was the presence of gaps ( P <0.001).

Conclusions— Modified CPVA is as effective as CPVA in preventing AF but is associated with a lower risk of developing incessant AT.

Radiofrequency ablation in children with asymptomatic Wolff-Parkinson-White syndrome

BACKGROUND

Ventricular fibrillation can be the presenting arrhythmia in children with asymptomatic Wolff-Parkinson-White syndrome. Deaths due to this arrhythmia are potentially preventable.

METHODS

We performed a randomized study in which prophylactic radiofrequency catheter ablation of accessory pathways was compared with no ablation in asymptomatic children (age range, 5 to 12 years) with the Wolff-Parkinson-White syndrome who were at high risk for arrhythmias. The primary end point was the occurrence of arrhythmic events during follow-up.

RESULTS

Of the 165 eligible children, 60 were determined to be at high risk for arrhythmias. After randomization, but before any ablation had been performed, the parents withdrew 13 children from the study. Of the remaining children, 20 underwent prophylactic ablation and 27 had no treatment. The characteristics of the two groups were similar. There were three ablation-related complications, one of which led to hospitalization. During follow-up, 1 child in the ablation group (5 percent) and 12 in the control group (44 percent) had arrhythmic events. Two children in the control group had ventricular fibrillation, and one died suddenly. The cumulative rate of arrhythmic events was lower among children at high risk who underwent ablation than among those at high risk who did not. The reduction in risk associated with ablation remained significant after adjustment in a Cox regression analysis. In both the ablation and the control groups, the independent predictors of arrhythmic events were the absence of prophylactic ablation and the presence of multiple accessory pathways.

CONCLUSIONS

In asymptomatic, high-risk children with the Wolff-Parkinson-White syndrome, prophylactic catheter ablation performed by an experienced operator reduces the risk of life-threatening arrhythmias.

Left atrial tachycardia after circumferential pulmonary vein ablation for atrial fibrillation

OBJECTIVES

The purpose of this study was to evaluate the electroanatomic characteristics of left atrial tachycardia (AT) in a series of patients who underwent circumferential pulmonary vein ablation (CPVA) and to describe the ablation strategy and clinical outcome.

BACKGROUND

Circumferential pulmonary vein ablation is an effective treatment for atrial fibrillation. A potential midterm complication is the development of left AT. There are only isolated reports describing mapping and ablation of such arrhythmias.

METHODS

Thirteen patients (age 57.4 +/- 8.9 years, five female) underwent mapping and ablation of 14 left ATs via an electroanatomic mapping system a mean of 2.6 +/- 1.6 months after CPVA.

RESULTS

Three patients were characterized as having focal AT (cycle length: 266 +/- 35.9 ms). Of 11 macro-re-entrant tachycardias studied in the remaining 10 patients (cycle length: 275 +/- 75 ms), 5 showed single-loop and 6 dual-loop circuits. Re-entrant circuits used the mitral isthmus, the posterior wall, or gaps on previous encircling lines. Such gaps and all three foci occurred anterior to the left superior pulmonary vein or at the septal aspect of the right pulmonary veins. Thirteen of 14 tachycardias (93%) were successfully ablated.

CONCLUSIONS

Left AT after CPVA can be due to a macro-re-entrant or focal mechanism. Re-entry occurs most commonly across the mitral isthmus, the posterior wall, or gaps on previous ablation lines. Such gaps and foci occur most commonly at the anterior aspect of the left superior pulmonary vein and at the septal aspect of the right pulmonary veins. These arrhythmias can be successfully mapped and ablated with an electroanatomic mapping system.

First human chronic experience with cardiac contractility modulation by nonexcitatory electrical currents for treating systolic heart failure: mid-term safety and efficacy results from a multicenter study

INTRODUCTION

Conventional electrical therapies for heart failure (HF) encompass defibrillation and ventricular resynchronization for patients at high risk for lethal arrhythmias and/or with inhomogeneous ventricular contraction. Cardiac contractility modulation (CCM) by means of nonexcitatory electrical currents delivered during the action potential plateau has been shown to acutely enhance systolic function in humans with HF. The aim of this multicenter study was to assess the chronic safety and preliminary efficacy of an implantable device delivering this novel form of electrical therapy.

METHODS AND RESULTS

Thirteen patients with drug-resistant HF (New York Heart Association [NYHA] class III) were consecutively implanted with a device (OPTIMIZER II) delivering CCM biphasic square-wave pulses (20 ms, 5.8-7.7 V, 30 ms after detection of local activation) through two right ventricular leads screwed into the right aspect of the interventricular septum. CCM signals were delivered 3 hours daily over 8 weeks (3-hour phase) and 7 hours daily over the next 24 weeks (7-hour phase). Safety and feasibility of this novel therapy were regarded as primary endpoints. Preliminary clinical efficacy, -as expressed by changes in ejection fraction (EF), NYHA class, 6-minute walking test (6-MWT), peak O(2) uptake (peak VO(2)), and Minnesota Living with HF Questionnaire (MLWHFQ), was assessed at baseline and at the end of each phase. At the end of follow-up (8.8 +/- 0.2 months), all patients were alive, without heart transplantation or need for left ventricular assist device. Serial 24-hour Holter analysis revealed no proarrhythmic effect. No devices malfunctioned or failed for any reason other than end-of-battery life. Throughout the two study phases, EF improved from 22.7 +/- 7% to 28.7 +/- 7% and 37 +/- 13% (P = 0.004), 6-MWT from 418 +/- 99 m to 477 +/- 96 m and 510 +/- 107 m (P = 0.002), MLWHFQ from 36 +/- 21 to 18 +/- 12 and 7 +/- 6 (P = 0.002), peak VO(2) from 13.7 +/- 1.1 to 14.9 +/- 1.9 to 16.2 +/- 2.4 (P = 0.037), and NYHA class from 3 to 1.8 +/- 0.4 to 1.5 +/- 0.7 (P < 0.001).

CONCLUSION

CCM therapy appears to be safe and feasible. Proarrhythmic effects of this novel therapy seem unlikely. Preliminary data indicate that CCM gradually and significantly improves systolic performance, symptoms, and functional status. CCM therapy for 7 hours per day is associated with greater dispersion near the mean, emphasizing the need to individually tailor CCM delivery duration. The technique appears to be attractive as an additive treatment for severe HF. Controlled randomized studies are needed to validate this novel concept.

Atrio-Esophageal Fistula as a Complication of Percutaneous Transcatheter Ablation of Atrial Fibrillation

BACKGROUND

Radiofrequency ablation for atrial fibrillation is becoming widely practiced.

METHODS AND RESULTS

Two patients undergoing circumferential pulmonary vein ablation for atrial fibrillation in different centers developed symptoms compatible with endocarditis 3 to 5 days after the procedure. Their clinical condition deteriorated rapidly, and both suffered multiple gaseous and/or septic embolic events causing cerebral and myocardial damage. One patient survived after emergency cardiac and esophageal surgery; the other died of extensive systemic embolization. An atrio-esophageal fistula was identified in both patients.

CONCLUSIONS

Atrio-esophageal fistulas can occur after catheter ablation in the posterior wall of the left atrium. This diagnosis should be excluded in any patient with symptoms or signs of endocarditis after left atrial ablation, and expeditious cardiac surgery is critical if the diagnosis is confirmed. Lower power and temperature settings for applications of radiofrequency energy along the posterior left atrial wall may prevent further cases of fistula formation.

Cardiac contractility modulation by non-excitatory electrical currents. The new frontier for electrical therapy of heart failure

Heart failure (HF) may complicate ischemic heart disease in both its acute and chronic manifestations, representing a prevalent health problem throughout the world. Development of therapies to improve heart function, relieve symptoms, reduce hospitalizations and improve survival is a high priority in cardiovascular medicine. The available pharmacological strategies, including angiotensin-converting enzyme inhibitors, angiotensin receptor antagonists, beta-blockers, and aldosterone receptor antagonists have recently been complemented by new electrical therapy, including implantable cardioverter-defibrillators for "MADIT II" patients and cardiac resynchronization for the 30% of HF patients with concomitant intraventricular conduction delay. The wide variety of available HF medications provides ample evidence that we have not yet succeeded in this effort. Safe and effective inotropic electrical therapy could be a useful addition to our therapeutic armamentarium in an attempt to correct Ca2+ fluxes abnormalities during the cardiac action potential. Cardiac contractility modulation (CCM) by means of non-excitatory electrical currents delivered during the action potential plateau has been shown to acutely enhance systolic function in humans with HF. Herewith, we report on our preliminary experience with CCM therapy for patients with HF, providing fundamental notions to characterize the rationale of this novel form of therapy. Briefly, CCM therapy appears to be safe and feasible. Proarrhythmic effects of this novel therapy seem unlikely. Preliminary data indicate that CCM gradually and significantly improves systolic performance, symptoms and functional status. The technique would appear to be attractive as an additive treatment for severe HF. Controlled randomized studies are needed to validate this novel concept.

Pulmonary Vein Denervation Enhances Long-Term Benefit After Circumferential Ablation for Paroxysmal Atrial Fibrillation

Background— There are no data to evaluate the relationship between autonomic nerve function modification and recurrent atrial fibrillation (AF) after circumferential pulmonary vein ablation (CPVA). This study assesses the incremental benefit of vagal denervation by radiofrequency in preventing recurrent AF in a large series of patients undergoing CPVA for paroxysmal AF.

Methods and Results— Data were collected on 297 patients undergoing CPVA for paroxysmal AF. Abolition of all evoked vagal reflexes around all pulmonary vein ostia was defined as complete vagal denervation (CVD) and was obtained in 34.3% of patients. Follow-up ended at 12 months. Heart rate variability attenuation, consistent with vagal withdrawal, was detectable for up to 3 months after CPVA, particularly in patients with reflexes and CVD, who were less likely to have recurrent AF than those without reflexes ( P =0.0002, log-rank test). Only the percentage area of left atrial isolation and CVD were predictors of AF recurrence after CPVA ( P <0.001 and P =0.025, respectively).

Conclusions— This study suggests that adjunctive CVD during CPVA significantly reduces recurrence of AF at 12 months.