Single-Center Experience of Catheter Ablation for Atrial Fibrillation Using Multi-Electrode Mapping and Ablation Catheters
- Volume 23 - Issue 10 - October 2011
- Posted on: 9/29/11
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Abstract: Purpose. Radiofrequency ablation (RFA) is an established therapy for the treatment of paroxysmal and persistent atrial fibrillation (AF). Many techniques have been reported to achieve RFA. We report a single-center experience of RFA using three multi-electrode catheters. Methods. We collected data of the patients who had RFA for AF using custom-designed multi-electrode mapping and ablation catheters between May 2007 and November 2009 at this center. Results. A total of 105 patients aged 56 ± 9.6 years underwent RFA using three multi-electrode catheters. Eighty-seven patients were new and 18 patients had re-do AF ablation using the multi-electrode mapping and ablation catheters. In the new patients, the mean procedure duration was 141 ± 38 minutes and fluoroscopy time was 38 ± 4 minutes. The mean duration of follow-up was 15.8 ± 6.4 months. Symptomatic improvement was achieved in 75 patients (86%), 48 patients (55%) remained in sinus rhythm (SR) after the first procedure, while 7 (8%) had multiple procedures and remained in SR without antiarrhythmic drugs (AAD). Fourteen patients (16%) required AAD following a single procedure and 1 patient (1.1%) after multiple procedures to remain in SR. Seven patients (8%) had reduced burden of symptoms. No improvement occurred in 12 patients (13.7%). In the 18 re-do patients, 15 (83.3%) had symptom improvement. Four patients (22.2%) remained in SR after a single procedure and 4 patients (22.2%) required multiple procedures to remain in SR without AAD. One patient (5.5%) remained in SR on AAD following a single procedure and 1 patient (5.5%) remained in SR on AAD following multiple procedures. Five patients (27%) had reduced burden of symptoms and 3 patients (16.6%) had no improvement. Conclusion. PVI using multi-electrode mapping and ablation catheters is an effective treatment of paroxysmal and persistent AF with a complication rate equivalent to published data.
J INVASIVE CARDIOL 2011;23(10):407–413
Key words: atrial fibrillation, percutaneous endocardial ablation, complications, PVI, success rate
Atrial fibrillation (AF) is a major health problem.1 The clinical consequences range from increased hospitalization, diminished quality of life, and increase in congestive heart failure, to devastating thromboembolic events and increase in mortality.2-6 Radiofrequency ablation (RFA) is an established therapy for selected patients with paroxysmal and persistent AF.7 The cornerstone of RFA for AF is the electrical isolation of the pulmonary veins (PVI), though in selected patients additional non-pulmonary vein lesions are performed.8 Traditionally, PVI is achieved using an irrigated single-tip catheter placing contiguous point-by-point lesions either targeting the electrical connections between the left atrium (segmental PVI) or by placing continuous circular lesions around the pulmonary veins (wide area circumferential ablation; WACA).9-11
However, such procedures can be technically complex and are associated with long fluoroscopy and procedure times. Recently, anatomically designed multi-electrode mapping and ablation catheters have been introduced in order to reduce procedure and fluoroscopy times and potentially simplify the procedure (Medtronic Ablation Frontiers, Medtronic, Inc.).12 The long-term efficacy of these catheters in comparison to a single-tip catheter-based approach is unknown and is currently under investigation by randomized trials.13 The aim of this single-center, retrospective, observational study was to analyze the safety and efficacy of the three multi-electrode catheters.
Population. Southampton University Hospital is a regional cardiac electrophysiology center for the Central South Coast Cardiac Network. We included consecutive patients who had undergone RFA for persistent or paroxysmal AF (May 2007 and November 2009) with an ablation strategy utilizing a circular catheter for pulmonary vein isolation (PVAC; Medtronic Ablation Frontiers), as well as custom-designed catheters for ablation of complex fractionated atrial electrograms (CFAE) on the septum and body of the left atrium.
Paroxysmal atrial fibrillation (PAF) was defined as recurrent AF (≥2 episodes) that terminated spontaneously within 7 days. Persistent AF was defined as AF that sustained for longer than 7 days, or that required electrical or chemical cardioversion.14,15
Patient selection. At present, there are no randomized clinical trials demonstrating improved survival or stroke reduction with RFA in AF, and therefore the procedure is predominantly reserved for symptomatic patients to improve quality of life. National and international guidelines advocate RFA to relieve symptoms in selected AF patients who are symptomatic despite anti-arrhythmic drugs (AAD) or who are intolerant to medication due to side effects.14,15 In our study, patients were selected for RFA consistent with these guidelines.
Preprocedure anticoagulation. All patients were anticoagulated with warfarin for a minimum period of 4 weeks preprocedure with a target INR of 2.0–3.0.16
Multi-electrode catheters and RF generator. The PVAC is a 9 Fr, over-the-wire, decapolar mapping and ablation catheter with an adjustable 25 mm diameter array at the distal portion (Figure 1A). The platinum electrodes are 3 mm long with 3 mm spacing. The shaft of the catheter can be deflected in both directions, facilitating correct positioning at each pulmonary vein antrum. Furthermore, the electrode array can be extended to assume a spiral configuration to enable different tissue contact and enhance mapping inside the PV. In addition, two other specifically designed multi-electrode catheters were used to target left atrial CFAE. The multi-array septal catheter (MASC; Medtronic Ablation Frontiers) is designed to target CFAE on the intra-atrial septum (Figure 1B), and the multi-array ablation catheter (MAAC; Medtronic Ablation Frontiers) CFAE in the left atrial body (Figure 1C).
The GENius multi-channel RF Ablation Generator (Medtronic, Inc.) is capable of independently delivering radiofrequency energy to a maximum of 12 electrodes simultaneously. Power can be delivered as unipolar energy, with current flowing from the catheter electrode to the dispersive electrodes on the patient’s back, or bipolar energy, with current flowing between two adjacent selected pairs of electrodes at the catheter array. The generator has 5 preset energy settings: bipolar, unipolar, and 3 ratios of bipolar/unipolar energy (4:1, 2:1, and 1:1).20 Preclinical studies have demonstrated that lesion depth is greater with energy settings with a greater proportion of unipolar energy, with lesion depths of up to 7 mm achievable.20 During RF application, energy delivery to individual electrodes is modulated to reach a user-defined target temperature.
Ablation procedure. A preprocedure cardiac MRI or CT scan was obtained in all patients to detect any anatomical anomalies as well as define pulmonary vein anatomy.17,18 In all cases, a preprocedural transesophageal echocardiogram was performed to look for left atrial thrombus.19
Procedures were performed in the fasting state under conscious sedation with local anesthesia. The ablation technique is described in detail elsewhere.20 In brief, vascular access was via the right femoral vein, right subclavian vein, and right femoral artery. A quadripolar catheter was placed in the coronary sinus (CS) for pacing and recording electrograms. A single transseptal puncture was performed with a Brockenbrough (BRK; Daig Corporation) or RF needle (NRG™ RF needle; Baylis Medical, Inc.) guided by fluoroscopy and contrast injection, and a 12.5 Fr steerable sheath (Channel; Bard Corporation) placed in the left atrium. Following transseptal puncture, systemic anticoagulation was achieved with a loading dose of 100 IU/kg intravenous unfractionated heparin followed by an infusion of 10 IU/kg/hour. During the procedure, the activated clotting time (ACT) was measured every 30 minutes and the heparin infusion rate was adjusted to maintain an ACT in the target range of 300–350 seconds.15
Prior to ablation, contrast angiography was used to define the PV as a reference for positioning the PVAC catheter. In all patients, isolation of PV was performed using the PVAC catheter. The steerable sheath was used to aid positioning of the PVAC catheter and a 0.032˝ guidewire was introduced into the targeted PV. The PVAC was then introduced into the antrum of the PV using an over-the-wire technique. In this study, RF energy was typically delivered to all electrode pairs for up to 60 seconds per application, using a 4:1 bipolar/unipolar energy ratio and a target temperature of 60 ˚C. The catheter was then rotated and further RF energy delivered if necessary. For potentials that were persistently detectable after ablation using a 4:1 energy ratio, further ablation using a 2:1 ratio was performed to achieve greater lesion depth.
Additional ablation of spontaneous CFAE with the MAAC and MASC catheters was performed in selected patients. CFAE were defined as electrograms with a cycle length ≤120 ms or shorter than the AF cycle length in the coronary sinus, or electrograms that were fractionated or displayed continuous electrical activity.8 Ablation of CFAE was performed in all patients with persistent AF and selected patients with PAF, especially those undergoing a re-do procedure. In patients who were in SR, AF was induced with burst atrial pacing in order to perform CFAE ablation.
The intraprocedural endpoints for PV isolation were entrance block into the PV during SR or CS pacing, and exit block during pacing from the PVAC in the PV distal to the ablation line. The CFAE was ablated until local activity was no longer observed. At the completion of the procedure, IV heparin was discontinued and sheaths were removed when the ACT was <160 seconds.15
Postablation management. All patients were monitored for 24 hours as an inpatient prior to discharge. Unless there were complications, warfarin was routinely restarted on the day of the procedure with subcutaneous low molecular weight heparin cover until the INR was ≥2. All patients were continued on an AAD for 6 weeks postablation and warfarin was continued (target INR, 2–3) until clinical follow-up.22
Follow-up, monitoring, and outcome measures. All patients were followed at our institution in an outpatient clinic at 3–6 months postprocedure. At follow-up, all patients had a 12-lead electrocardiogram (ECG) and were clinically assessed to evaluate their symptom burden. Twenty-four hour and 7-day rhythm monitoring was performed in selected patients depending on symptomatic status.21