Robotic and magnetic navigation for atrial fibrillation ablation. How and why?

Catheter ablation techniques for atrial fibrillation are evolving with targets for radiofrequency ablation of atrial fibrillation increasingly being selected based on anatomic considerations. Such anatomic ablation techniques require precise catheter localization and stable contact during ablation. Even experienced electrophysiologists occasionally encounter difficulties in maintaining stable catheter contact, especially in some regions of complex anatomy where catheter stability is crucial. Limitations of manually deflected conventional ablation catheters in performing complex catheter maneuvers may also contribute to these challenges. The CARTO RMT version 8 has been recently released to guide left atrial mapping and ablation in conjunction with the Stereotaxis system for remote control of the ablation catheter. We aim to describe how this system works and why it is needed in the field of catheter ablation.

Transcatheter radiofrequency ablation of atrial fibrillation in patients with mitral valve prostheses and enlarged atria: safety, feasibility, and efficacy.

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.

Electroanatomic remodeling of the left atrium in patients undergoing repeat pulmonary vein ablation: mechanistic insights and implications for ablation.

INTRODUCTION: There is limited information describing late changes in the electroanatomic characteristics of the left atrium (LA) associated with recurrence after an anatomical circumferential pulmonary vein ablation (CPVA) for atrial fibrillation (AF). METHODS AND RESULTS: Forty-seven patients (57 +/- 8 years) undergoing a repeat ablation after CPVA were included. Using an electroanatomic mapping system, we measured the bipolar voltage by averaging points in the pulmonary vein (PV)-LA junction and four other LA sites. Conduction velocity and AF cycle length (AFCL) were also measured and the results are compared with the first procedure. After an initial decrease observed at the end of the first procedure, voltage and conduction velocity returned to intermediate values in all LA sites, with lower voltage at the LIPV antrum (P = 0.004), and lower conduction velocity across the LIPV and RSPV (P < 0.001). Conduction gaps were more prevalent at the septal aspect of the right PV encircling lines (85%), between the left atrial appendage (LAA) and the LSPV (70%) and lines at the posterior wall (71%). There was a nonsignificant increase in AFCL, with a more widespread distribution of organized electrograms (32.4% vs 46.6%). CONCLUSION: Recurrence after CPVA is associated with a reverse process of voltage and conduction velocity increase across ablated areas, especially the PV-LA junction, and is related to the presence of conduction gaps, which are distributed mostly at the septal aspect of the lines encircling the right PVs and at the LAA-LSPV area. Organization of atrial electrograms seen during AF ablation is maintained at a repeat procedure.

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.

Prevention of iatrogenic atrial tachycardia after ablation of atrial fibrillation: a prospective randomized study comparing circumferential pulmonary vein ablation with a modified approach.

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.

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.

Mortality, morbidity, and quality of life after circumferential pulmonary vein ablation for atrial fibrillation: outcomes from a controlled nonrandomized long-term study.

OBJECTIVES: This study was designed to investigate the potential of circumferential pulmonary vein (PV) ablation for atrial fibrillation (AF) to maintain sinus rhythm (SR) over time, thus reducing mortality and morbidity while enhancing quality of life (QoL). BACKGROUND: Circumferential PV ablation is safe and effective, but the long-term outcomes and its impact on QoL have not been assessed or compared with those for medical therapy. METHODS: We examined the clinical course of 1,171 consecutive patients with symptomatic AF who were referred to us between January 1998 and March 2001. The 589 ablated patients were compared with the 582 who received antiarrhythmic medications for SR control. The QoL of 109 ablated and 102 medically treated patients was measured with the SF-36 survey. RESULTS: Median follow-up was 900 days (range 161 to 1,508 days). Kaplan-Meier analysis showed observed survival for ablated patients was longer than among patients treated medically (p < 0.001), and not different from that expected for healthy persons of the same gender and calendar year of birth (p = 0.55). Cox proportional-hazards model revealed in the ablation group hazard ratios of 0.46 (95% confidence interval [CI], 0.31 to 0.68; p < 0.001) for all-cause mortality, of 0.45 (95% CI, 0.31 to 0.64; p < 0.001) for morbidities mainly due to heart failure and ischemic cerebrovascular events, and of 0.30 (95% CI, 0.24 to 0.37; p < 0.001) for AF recurrence. Ablated patients' QoL, different from patients treated medically, reached normative levels at six months and remained unchanged at one year. CONCLUSIONS: Pulmonary vein ablation improves mortality, morbidity, and QoL as compared with medical therapy. Our findings pave the way for randomized trials to prospect a wider application of ablation therapy for AF.

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.

A randomized trial of circumferential pulmonary vein ablation versus antiarrhythmic drug therapy in paroxysmal atrial fibrillation: the APAF Study.

OBJECTIVES: We compared ablation strategy with antiarrhythmic drug therapy (ADT) in patients with paroxysmal atrial fibrillation (PAF). BACKGROUND: Atrial fibrillation (AF) ablation strategy is superior to ADT in patients with an initial history of PAF, but its role in patients with a long history of AF as compared with ADT remains a challenge. METHODS: One hundred ninety-eight patients (age, 56 +/- 10 years) with PAF of 6 +/- 5 years' duration (mean AF episodes 3.4/month) who had failed ADT were randomized to AF ablation by circumferential pulmonary vein ablation (CPVA) or to the maximum tolerable doses of another ADT, which included flecainide, sotalol, and amiodarone. Crossover to CPVA was allowed after 3 months of ADT. RESULTS: By Kaplan-Meier analysis, 86% of patients in the CPVA group and 22% of those in the ADT group who did not require a second ADT were free from recurrent atrial tachyarrhythmias (AT) (p < 0.001); a repeat ablation was performed in 9% of patients in the CPVA group for recurrent AF (6%) or atrial tachycardia (3%). At 1 year, 93% and 35% of the CPVA and ADT groups, respectively, were AT-free. Ejection fraction, hypertension, and age independently predicted AF recurrences in the ADT group. Circumferential pulmonary vein ablation was associated with fewer cardiovascular hospitalizations (p < 0.01). One transient ischemic attack and 1 pericardial effusion occurred in the CPVA group; side effects of ADT were observed in 23 patients. CONCLUSIONS: Circumferential pulmonary vein ablation is more successful than ADT for prevention of PAF with few complications. Atrial fibrillation ablation warrants consideration in selected patients in whom ADT had already failed and maintenance of sinus rhythm is desired. (A Controlled Randomized Trial of CPVA Versus Antiarrhythmic Drug Therapy in for Paroxysmal AF: APAF/01; http://clinicaltrials.gov/ct/show; NCT00340314).

Left atrial tachycardia after circumferential pulmonary vein ablation for atrial fibrillation: electroanatomic characterization and treatment.

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.