Combined Endocardial and Epicardial Ablation for Atrial Fibrillation: Single Center Experience
Much debate has been made between cardiothoracic surgeons and electrophysiologists regarding the best way to treat patients who have drug resistant atrial fibrillation. Although surgical procedures, such as the “Cut and Sew” Cox - Maze have been successful in the treatment of atrial fibrillation it requires cardiopulmonary bypass and has a higher rate of bleeding and need for permanent pacing.[i] The invasive nature of this procedure and number of surgeons who perform the procedure has also limited its use. Minimally invasive surgical ablation procedures, such as the “Mini-Maze” have not resulted in the success rates of open chest procedures.[ii] [iii]
Percutaneous pulmonary vein atrum isolation has also been challenging for electrophysiologists and has not been demonstrated to result in the efficacy that has been seen in the Cox Maze for patients with persistent and permanent atrial fibrillation.[iv] [v] [vi]
The Convergent procedure was developed to create a complete and comprehensive pattern of linear lesions under direct endoscopic visualization, while avoiding chest incisions, deflation of the lungs, and invasive heart dissections that has hindered electrophysiologist adoption of surgical ablation. It takes a multidisciplinary treatment to produce a complete comprehensive lesion pattern as both epicardial and endocardial ablation are required. Following ablation, standard EP testing is used to confirm isolation of the pulmonary veins and the posterior left atrium.[vii] The purpose of this paper is to present our outcomes of the multidisciplinary Convergent procedure for the treatment of paroxysmal, persistent and longstanding persistent AF patients.
Between May 2010 and December 2011, the first 104 AF patients received the Convergent procedure at Our Lady of the Lake Regional Medical Center, Baton Rouge, LA. Patients were between the ages of 37-79 years and had documented AF based on the Heart Rhythm Society definitions.[viii] Paroxysmal, persistent, and permanent AF patients were selected to undergo the Convergent Procedure. The paroxysmal patients were selected only if they had a high AF burden. Patients were excluded if they had prior open heart surgery or a major abdominal procedure.
The Convergent Procedure
The procedure combines the expertise of both a cardiothoracic surgeon and electrophysiologist for the treatment of AF. In all patients, epicardial ablation was performed before endocardial mapping and ablation. Epicardial ablation is performed through a transdiaphragmatic access without chest incisions or ports, deflation of the lungs, or heart dissections.[ix] Because the pericardial reflections between the left atrium and pericardium are not dissected, there are gaps between the continuous linear epicardial lesions. These known breakthrough locations are mapped and connected endocardially to complete the comprehensive pattern, as shown in Figure 1. After endocardially completing the pattern, electrophysiology testing is performed to assure lesion transmurality, pattern completeness, and PV isolation.
Description of Convergent Procedure
By definition, the Convergent procedure is the completion of both epicardial and endocardial components of the procedure. The procedure was performed under general anesthesia. Both the epicardial ablation and endocardial ablation were performed in the EP laboratory. Perioperative anticoagulation consisted of cessation of warfarin three days before the procedure and initiation of aspirin 325 mg daily. Patients with a CHADS score > 2 were bridged with Enoxaparin prior to the procedure. Transesophageal echocardiography was performed on all patients to exclude LA thrombus the morning of the ablation.
An esophageal temperature probe was inserted to monitor esophageal temperature during both the epicardial and endocardial ablation.
The patient was prepped and draped for both abdominal epicardial access and catheterization through the femoral veins. Endocardial ablation was performed immediately after epicardial ablation and closing of abdominal access incisions.
Transdiaphragmatic Access and Epicardial Ablation Procedure
Access to the posterior surface of the heart was achieved via a transdiaphragmatic pericardial window created endoscopically under CO2 insufflation using a 5 mm Optiview trocar inserted in the left upper quadrant of the abdomen for laparoscopic exploration (Figure 2, A-B). An additional trocar (10/12 mm) is inserted in the subxyphoid region and a 5 mm trocar in the right upper quadrant. A pericardioscopic cannula (nContact Inc., Morrisville, NC, USA) is inserted through the pericardial window and manipulated throughout the pericardial space to allow for positioning the epicardial ablation electrode (Figure 2, C-D). After access to the posterior of the heart is achieved, long linear lesions of the comprehensive biatrial pattern (Figure 2, E-F) are created under direct endoscopic visualization without dissecting the pericardial reflections.[x] Epicardial ablation is performed along the posterior left atrium and around the antrum of the pulmonary veins. The average total skin-to-skin time for the epicardial component of the convergent procedure was 84 (± 21.6) minutes with an average RF ablation time of 34.7 (±7.7) minutes.
All epicardial lesions were created using the Numeris® Coagulation System (nContact, Inc., Morrisville, NC, USA), which utilizes a vacuum irrigated unipolar radiofrequency (RF) electrosurgical device with a 3 cm long directional ablation electrode. Suction applied to the probe ensures consistent contact with epicardial tissue. Irrigation prevents spread of thermal injury and cools the tissue surface, which allows for concentrated, focused energy. The system provides audible (cessation of the suction hiss sound when complete device to epicardial tissue vacuum seal is achieved) and visible confirmation of contact (initiation of saline perfusion upon completion of the vacuum seal). The RF generator uses an algorithm based on the electrical resistance of the tissue to modulate power delivery to the lesion to avoid popping and over-desiccation.
Transseptal Access and Endocardial Catheter Ablation Procedure
Percutaneous access to the left atrium is obtained through a conventional double transseptal puncture. Four venous accesses were obtained: Two 8-French sheaths in the right femoral vein, one 11-French sheath and and one 8-French sheath in the left femoral vein. Using standard electrophysiological ablation techniques, endocardial lesions are created to connect the epicardial linear lesions along the pericardial reflections. The technique of pulmonary vein antrum isolation has been described extensively elsewhere.[xi] Briefly, a 3.5 mm irrigated tip catheter (Navistar Thermocool®, Biosense Webster, Diamond Bar, CA, USA) was used to create endocardial lesions. ICE was used to identify pulmonary vein antra, to guide radiofrequency delivery and to look for potential complications. Electroanatomical mapping was performed using the CARTO system. RF energy was set on 35 W up to 40 W and to no more than 41 ºC catheter tip temperature. When ablating on the posterior wall if needed power was reduced to 25 Watts. EP testing was performed to confirm PV isolation.
Antiarrhythmic drug (AAD) therapy was started immediately after the procedure and continued for eight weeks. Anticoagulation was reinitiated postoperatively and continued for at least 5 months.
Patients were seen by the surgeon for wound inspection at 1 month and by the electrophysiologist for a physical exam and EKG at 1-, 3-, 6- and 12-months. AAD and were also recorded at each follow-up visit. Two months post procedure was defined as a blanking period. During the blanking period, any treated or untreated AF/AFL episodes were not considered treatment failures. All patients were monitored for at least 72 hours at 6 months and at a year. Interrogation of implanted devices were also performed.
Continuous data were described as mean +/- standard deviation (SD) or as mean (range) for skewed distributions. Baseline and follow-up values are reported as mean ± standard deviation (SD) for numeric measures, and counts and percents for categorical measures.
104 patients receiving the Convergent Procedure were included in the study, all of which underwent treatment in a single setting.
Table 1 summarizes the baseline clinical characteristics of the study population. The median patient age was 60.9, and a majority of the patients were male (77%). Twenty-eight percent of the patients (28/104) were paroxysmal, thirty percent (31/104) were persistent, and forty three percent (45/104) were permanent. Seventy-eight percent (39/50) of the patients had structural heart disease. The average left atrial size was 4.1 cm based on transthoracic echocardiography measurements.
Total Procedure time including both the Epicardial and Endocardial Procedure was 212.7 (+/- 22.9) minutes. Median Procedure time (skin to skin) for the epicardial ablation was 84.1 (+/- 21.6) minutes and epicardial ablation time was 34.7 (+/- 7.7) minutes. The total time of the endocardial ablation was 128.7 (+/- 28.7) minutes. Fluoroscopy time was 19.1 (+/- 7.4) minutes. Pulmonary veins were successfully isolated in all patients. Average ICU stay was 1 (+/- 0.4) days and Average Length of Stay was 3 (+/- 0.8) days.
Safety data for the study is described in Table 2. There were no Major Adverse Events < 30 days post procedure. After 30 days we observed, one cerebral vascular accident in a patient with of permanent AF and severe LV dysfunction (EF 30%) who presented to the ER with stroke symptoms in sinus rhythm. There was one pericardial effusion (>30 days after procedure) that did require drainage and two pleural effusions. There was one case of pulmonary vein stenosis that required stenting.
Efficacy outcomes are detailed in Table 3. At 12 months post procedure 72% (52/72) of patients were in Sinus Rhythm off Anti-Arrhythmic Drugs (AAD) and 87.5% (63/72) were in Sinus Rhythm +/- AAD. At Last Follow up (215 days) 73% (76/104) were in Sinus Rhythm off AAD and 89% of patients (93/104) were in Sinus Rhythm +/- AAD. Three patients underwent a repeat catheter ablation procedure.
Efficacy outcomes were also looked at based on AF type. Parosysmal, Persistent, and Permanent AF patients at 12 months had success of 72%, 84%, and 62% off of AAD and 89%, 88%, and 86% +/- AAD. Table 4 shows outcomes based on AF type at 1 year and at time of last follow up.
To date this is the largest study assessing the safety and outcomes of the Convergent Procedure for the treatment of atrial fibrillation. We have demonstrated that the procedure is effective and safe. The percentage of patients free from atrial fibrillation and at 1 year was 72% not using anti-arrhythmic drugs and 87.5% +/- anti-arrhythmic drugs.
Even though this was our early experience with a small number of patients, these results make this technique a promising approach to the treatment of AF. In our view, the collaboration between surgeon and electrophysiologist is beneficial to the outcome of the procedure since it allows electrophysiologists and surgeons to work in a collaborative rather then a competitive fashion, and as a result it has allowed one to cover the weaknesses of the other. The surgical approach allows for a complete lesion set on the posterior wall and around the pulmonary veins but is weak in mapping and is unable to reliably complete a cavotricuspid ablation line. The EP catheter-based approach allows for completion of the pulmonary vein isolation at the pericardial reflections and meticulous testing of block. Using epicardial and endocardial ablation we can also overcome the challenges seen in achieving transmurality of ablation lesions.
Effect on AF Type
In our patients we elected to treat paroxysmal, persistent, and permanent atrial fibrillation. Although pulmonary vein isolation is now established as the corner stone for ablation of paroxysmal atrial fibrillation it is not effective in all patients. Since there is a continuum of arrhythmia burden in the paroxysmal AF population we elected to choose patients who had a high AF burden since we felt additional substrate modification and complete posterior wall isolation would be required to improve outcomes.
In our experience, paroxysmal AF patients did not have higher success rates then persistent AF patients off of anti-arrhythmic drugs. This may have been reflected by a higher incidence of both post ablation right atrial and left atrial flutter seen in the paroxysmal group. Later in our experience we included cavotricuspid lines empirically in all parosysmal patients due to an increased finding of failures due to typical right atrial flutter as well as the common finding of induction of right atrial flutter during burst pacing after completion of the left sided lesions. Post ablation left atrial flutter was not a common finding so we did not feel the need to perform a mitral isthmus ablation on all patients unless they had a documented LA flutter. Further study of the paroxysmal patient population will need to be performed to elucidate this issue.
Single center experience previously reported using the Convergent procedure demonstrated 87% of persistent and long standing persistent patients had less than 3% AF burden verified by implantable loop recorders at 24 months. This success rate unfortunately carried a major complication rate of 10% including mortality secondary to atrial esophageal fistula and CVA, pericardial effusion, and excessive bleeding. [xii] Based on the early experience learned from this study on how to mitigate the risks of the procedure we were able to decrease the complication rate. In our series, we did not experience any atrial esophageal fistulas, but did report one CVA, one pericardial effusion without tamponade, and one case of pulmonary vein stenosis. Further experience and development of a standardized lesion set, continued vigilance to improve safety will hopefully help us work toward achieving a higher success rate while keeping complications equivalent to that seen with stand alone percutaneous catheter ablation.
Epicardial Connections and Hybrid Ablation
Despite the adoption of catheter ablation for treatment of patients with atrial fibrillation the success rate needs to improve. It has been reported that as much as 20% of electrical impulses arising from the pulmonary veins might be propagated through pathways other than the venoatrial continuity at the veins ostium, such as epicardial connections with a nearby PV or epicardial venoatrial connections at a distance from the ositium.[xiii] These connections may be responsible for some recurrence seen with catheter based endocardial ablation and offers a clear rationale for the epicardial approach. Electrophysiologist and surgeons have shown that they can work together to improve the safety and efficacy of hybrid ablations and we are learning that there are advantages of a combined endocardial and epicardial approach.[xiv]
Despite some early promise, some would argue that the given the invasiveness of a surgical procedure that surgery should be limited to failed endocardial cases or for treatment of longstanding persistent atrial fibrillation. Our interpretation of the published literature shows that catheter ablation success is still in need of improvement and the invasiveness of a hybrid procedure has not resulted in an unacceptable complication rate. Furthermore, the perceived logistical problems of a hybrid strategy[xv] were overcome at our institution by performing the ablation in the EP lab with a total procedure time of less than four hours.
This was a retrospective assessment of the safety and effectiveness of the Convergent Procedure although all the data were collected and entered in a prospective database.
The convergent procedure, a hybrid approach for AF, is a safe and successful procedure with a procedure success rate of 72% at 1 year without the use of AAD. The clinical implications of our findings are relevant in helping cardiologist, electrophysiologist, and surgeons determine which is the best procedure to chose when recommending AF ablation for their patients.
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