Publication/Presentation Date

7-31-2015

Abstract

Outcomes of Convergent Ablation Procedure using a Cryo-balloon Catheter for Treatment of Atrial Fibrillation

Rosalie Mattiola, Bryan Auvil, James K. Wu, MD, Gregory Altemose, MD,

From the Division of Cardiothoracic Surgery, Department of Surgery, Lehigh Valley Health Network, Allentown, Pennsylvania.

BACKGROUND

Traditional catheter based treatment for atrial fibrillation (AF) uses radiofrequency as a source of energy for the ablation of atrial tissue. This is an endocardial (inside the heart) technique. The success rate of this technique at one year is around 50-60%1. In the last three years, a novel technology using a combined/hybrid trans-diaphragmatic surgical epicardial (outside the heart) ablation with endocardial (inside the heart) ablation techniques have had one-year success rates close to 80%2. This is called the Convergent Procedure (CP) 3. The CP can be done with either radiofrequency ablation (RF), or with a cryo-balloon catheter to create the endocardial lesion set. The cryo-balloon technique may be a preferred approach, as it creates improved endocardial coverage of the pulmonary veins. Limited data is available on the cryo-balloon technique for CP.

OBJECTIVE

To evaluate the effectiveness and patient outcomes of utilizing the cryo-balloon ablation technique in the setting of the Convergent Procedure(CP).

METHODS

From October 2013 to May 2015, thirty-one AF patients underwent the convergent procedure with cryo-balloon endocardial ablation at LVHN. Patients were managed postoperatively medically with amiodarone, steroids, anticoagulants, and anti-inflammatories. Follow-up visits occurred 1 month, 3 months, 6 months, and 12 months after the surgery. Most (89%) patients received an implantable monitoring device that was interrogated at each visit for arrhythmias.

Medical records were reviewed to determine pre-operative comorbidities and post-operative outcomes. Descriptive statistics were utilized to analyze the data.

RESULTS

Of the atrial fibrillation patients undergoing a convergent procedure with a cryo-balloon, 30% suffered from paroxysmal AF; 70% from persistent or chronic AF. Arrhythmia-free survival after the convergent procedure using a cryo-balloon catheter, including repeat ablation was 92% three months post-operatively and 89.5% six months post-operatively. One patient required a repeat ablation post-operatively. There were no deaths. Major complications included one patient experiencing pericardial effusion and one with hemoperitoneum.

CONCLUSIONS

This study of 31 patients suggests that the use of a cyro-balloon catheter for endocardial ablation during the convergent procedure is a viable method to eliminate the recurrence of persistent atrial fibrillation and arrhythmias. Further study is warranted that obtains a larger sample size of CP patients and allows more time between operation and follow-up data collection. Other data should be collected on the time efficiency of the cryo-balloon versus radiofrequency technique.

KEYWORDS

Atrial fibrillation, Catheter ablation, Hybrid ablation, Cryo-ablation, Cryo-balloon catheter, Outcomes

ACRONYMS

AF= Atrial fibrillation; CP= Convergent Procedure; RF= Radiofrequency; ACT= Activated clotting time

Introduction

Atrial fibrillation (AF) is the most common abnormal heart rhythm, effecting approximately 2.2 million individuals in the United States4. AF can be treated medically, and/or by means of shocking the heart back into rhythm via cardioversion(s) and/or by ablating electrical tissue of the posterior heart. Patients with AF whom experience persistent symptoms even after receiving the above treatments are considered appropriate candidates for the hybrid epicardial/endocardial-ablating convergent procedure (CP). Traditionally, ablations utilize radiofrequency (RF) energy as a means to cauterize the electrical tissue of the heart. The epicardial portion of the convergent procedure uses this such technique. However, for the second portion of the procedure, it may be more effective to utilize a cryo-balloon catheter to freeze the endocardial tissue rather than cauterizing it with a RF source. The endocardial segment of the CP is conducted by an electrophysiologist who feeds a catheter thru the femoral artery to the posterior aspect of the heart. The RF catheter tip requires approximately 30 small burns around the pulmonary veins to isolate all electrical conduction that could disturb the heart’s sinus rhythm. The cryo-balloon catheter requires only 8-14 lesions to freeze the electrical tissue around the pulmonary veins.

Figure 1: Radiofrequency Endocardial Ablation8

Figure 2: Cryo-balloon Endocardial Abaltion11

Figures 1 and 2 show cross sections of the heart exposing the left atrium and interior pulmonary vein ostia. The first figure depicts the radiofrequency circumferential mapping process while the second figure animates cryo-balloon occlusion in one of the pulmonary vein ostium.

Methods

Study Population

Between October 2013 and May 2015, thirty-seven AF patients underwent the convergent procedure at Lehigh Valley Hospital at Cedar Crest in Allentown, Pennsylvania. The cryo-balloon technique was used on 31 of those 37 patients to isolate the endocardium. RF ablations were applied to the other 6 patients. Patients met criteria to undergo the convergent procedure if they experienced symptomatic AF for an extended period of time, and/or if they had a history of failed medical therapies, cardioversions or traditional ablations for treatment of AF. Patients were excluded from the study if they were administered RF ablations during the endocardial portion of their CP.

Ablation Procedure

The Convergent Procedure is divided into two parts; epicardial and endocardial. The epicardial portion is performed by a cardiothoracic surgeon.

To begin, general anesthesia is induced and maintained throughout the entire case. An esophageal temperature probe is placed and the patient is prepped and draped in the usual sterile fashion. A small incision is made in the midline, approximately 2 cm below the xiphoid process. The surgeon then enters the peritoneal cavity using a modified Hassan technique. Two

additional 5-mm trocars are placed in the midclavicular line, on either side. This is done under direct palpation. The abdomen is then insufflated with carbon dioxide to achieve a pneumoperitoneum. The surgeon identifies the falicform ligament and creates a pericardial window in the central tendon of the diaphragm. Next, the surgeon guides the nContact cannula into the pericardial space and removes the 5-mm trocars. The posterior aspect of the left atrium is then ablated with a radiofrequency device for 90 seconds per ablation in a linear fashion from the left pulmonary veins to the right pulmonary veins. A double lesion set is created. The nContact cannula is then flipped to access and ablate the anterior surface of the right and left pulmonary veins. Total lesions range from 16 to 23. Finally, a drain is placed into the pericardial space and exited out one of the 5-mm trocar sites. The fascia and skin are repaired in the usual fashion. The case is then turned over to an electrophysiologist for the endocardial portion.

The electrophysiologist begins by assuring the groin area is clipped, prepped and draped in the usual sterile fashion. Local anesthesia is applied to the groin and a transseptal catheterization is performed under fluoroscopic and hemodynamic guidance. A one-puncture transseptal access is performed using a Brockenbrough needle assembly with a long sheath. Once the catheter is across the atrial septum, heparin is immediately infused and dosed to maintain an activated clotting time (ACT) of > 300 seconds. CT levels are assessed every 15 minutes throughout the procedure. Next, right femoral vein access is obtained for catheter placement. The vessel is accessed using the modified Seldinger technique. Similarly, left femoral vein access is obtained for electrode placement. Then, right internal jugular vein access is obtained for coronary sinus catheter placement. Using an Intracardiac echocardiography (ICE), a catheter is then advanced into the right atrium. An echocardiography is used to guide the transseptal puncture, guide catheter positioning, measure the diameter of the pulmonary vein ostia, ensure proper contact between the ablation catheter and the endocardium, measure pulmonary venous blood flow velocity before and after ablation, and identify esophagus location relative to posterior left atrium. At the conclusion of the procedure, ICE imaging is used to ensure there is no evidence of pericardial effusion.

After the catheter enters the right atrium, electrophysiologic testing is performed and measurements of basic intervals and refractory periods are obtained. Catheters are positioned in the high right atrium, right ventricular apex, left atrium and His-bundle region for pacing and recording. Arrhythmia induction protocols include programmed stimulation without acute drug testing. A shell of the pulmonary veins and the left atrium was made prior to surgery using the EnSite Velocity10 3-D mapping system. The anatomy of the pulmonary veins are determined in this manner. A 20mm Achieve circular mapping catheter is then positioned within each of the individual pulmonary vein ostia. Pulmonary vein potentials are determined in all four veins. The electrophysiologist ensures the occlusion of each pulmonary vein and then employs a “freeze-thaw-freeze” strategy which ultimately delivers two lesions per vein. Occlusion is determined by repeat contrast pulmonary venography and lack of color flow via ICE imaging. The cryo-balloon is inflated with a liquid refrigerant (liquid nitrogen). The refrigerant evaporates and scars the tissue of the occulted pulmonary vein, thus

Figure 3: Cryo-balloon catheter5

eliminating any electrical conduction that could interfere with electrical currents in the atria and cause atrial fibrillation6. The Arctic Front Advance 23mm or 28mm cyro-balloon ablation catheter is positioned at the ostium of the left superior pulmonary vein, left inferior pulmonary vein, right superior pulmonary vein and right inferior pulmonary vein. Each vein receives a 1 to 3 lesions which results in the isolation of each respective vein. The total lesion time ranges from 1353 to 2674 seconds.

Figure 4: Complete Pulmonary Vein Isolation

This image depicts the shell of the pulmonary veins of a LVHN CP patient. The grey area represents electrical isolation on scarred tissue.

Postoperative management
Patients were restarted on their normal medication after the procedure. Additionally, at least 77% of the patients received the following medical therapy; an anticoagulant (heparin, coumadin, eliquis) and an anti-inflammatory (colchicine) administered 6-12 hours after the operation. An intravenous steroid (salumedrol; methoprednisolin) administered for 2-3 days post-operatively and amiodarone taken for 6-8 weeks to manage lingering arrhythmias. To thoroughly record both asymptomatic and symptomatic arrhythmia episodes, 89% of the patients received remote monitoring devices (41% Lifewatch EM, 8 % ILR, 22% PPM-dual, 7 % ICD-Dual 11% Holter, 11% None).

Figure 5: Implantable Monitoring Devices

Follow Up

Patients were seen in the office at 1 month, 3 month, 6 month, and 12 month intervals when applicable. At each visit, monitoring devices were interrogated and/or echocardiograms were administered to determine heart rhythm. Recurrent arrhythmias were defined as episodes lasting greater than 1 minute or accounting for greater than a 2% burden as recorded by a monitoring device. Medications were also adjusted and other therapies were scheduled as needed.

Results

Table 1: Study Population Demographics

Characteristic

Subjects

N

31

Age (years), mean (range)

66 (40-81)

Sex:Male, n (%)

23 (74.2)

Paroxysmal AF, n (%)

9 (30)

Persistent AF, n (%)

22 (70)

Hypertension, n (%)

23 (74.2)

Obesity, n (%)

8 (25.8)

Congestive Heart Failure, n (%)

9 (29)

Current/Past Tobacco Use, n (%)

14 (48.3)

Sleep Apnea, n (%)

11 (34.4)

Pacemaker, n (%)

7 (22.6)

Previous Ablation, n (%)

13 (38.7)

Previous Cardioversion, n (%)

17 (54.8)

Family Hist. HD, n (%)

13 (43.3)

N = population size; SD = standard deviation; n= number; AF=

atrial fibrillation; HD= heart disease

The patients were between the ages of 40 and 81 at the time of the procedure. The average age was 66 years old. Male patients defined 67.5% of the study population. All patients were of white race. Patients had either paroxysmal, persistent, or longstanding persistent (chronic) AF.

76.6% (23/30) of patients were in sinus rhythm at every follow up. At 3 months, 100% (26/26) of patients were free of atrial fibrillation while 92% (23/25) of patients that received the full convergent procedure were arrhythmia-free. Six months after their operation, 94.7% (18/19) of patients were AF-free while 89.5% (17/19) were arrhythmia-free. Twelve month post-operative data was only available for 6 patients. All of these patients (100%) were arrhythmia and AF- free.

Table 2: Post-operative outcomes

AF-free

Arrhythmia-free

3 months

100%

92%

6 months

94.7%

89.5%

12 months

100%

100%

Heart rhythm was determined by interrogating monitoring devices and/or by administering echocardiograms. A total of 5 patients did experience recurrent arrhythmias after the convergent procedure using a cryo-balloon catheter. Three out of five experienced post-operative recurrent atrial flutter and were cardioverted back into sinus rhythm. One of these three patients only received endocardial ablations due to liver adhesions, leaving the surgeon to abort the epicardial portion of the CP. One patient experienced symptomatic atrial tachycardia and received another traditional ablation along with cardioversions. One patient experienced irregular rhythm after an epicardial-only ablation. This patient received endocardial ablation 3 months later, but did experienced recurrent atrial fibrillation without palpitations before returning to sinus rhythm. Overall, 3.2% (1/30) of patients required repeat ablation and 12.9% (3/30) required post-operative cardioversion due to recurrent arrhythmias.

Figure 6: Post-operative Therapies in response to Recurrent Arrhythmia

Analysis

Literature Review

Literature on the convergent or “hybrid ablation” procedure is heavily concentrated on radiofrequency ablation for both epicaridal and endocardial segments. A Polish study found 72.2% (13/18) of their patients in sinus rhythm 6 months after the procedure and 80% (8/10) in sinus rhythm after 12 months2. Civello, et al., reports 89% of their patients (93/104) in sinus rhythm approximately 6 months post- operatively7. Gehi, et al., reports a 12-month arrhythmia free survival of 70.5% and a repeat ablation rate of 6%3.

Traditional radiofrequency catheter ablation alone has much lower success rates. A 43 patient study reports 56.5% in normal sinus rhythm using antiarrhythmic drugs six months after the ablation1 . Another endocardial-only radiofrequency ablation study provides 12 month results of 68% arrhythmia-free survival9.

Figure 7: Success of Convergent Procedure using Cryo-balloon catheter

Discussion

Procedural Complications

Overall, procedural complications were very limited. A total of two patients (6.4%) experienced adverse-effects from the operation. Although several measures are taken to avoid effusion including administering anti-inflammatory drugs, one patient experienced pleural effusion 4 days post-operatively. This patient required reoperation for drain insertion. He recovered and was discharged the next day. The other patient experienced hemoperitoneum with a hematoma around on the trocar sites secondary to their anticoagulated state following surgery. The patient was re-operated on and had hematomas evacuated with suction and controlled with cautery. The patient was discharged 4 days after the convergent procedure and recovered successfully. There were no procedural mortalities, no atrioesophogeal fistulas, and no pericardial tamponade.

Table 3: Major Complications

N

31

Procedural Mortality

0

Atrioesophageal fistula

0

Pericardial effusion

1

Pericardial tamponade

0

Bleeding

1

Total

2 (6.4%)

Study Limitations

The study included only patients with symptomatic AF. This was a retrospective study of the effectiveness of cryo-balloon ablation for eliminating the recurrence of AF. No quality of life surveys were collected. A control group of RF ablations was not studied; rather the control group statistics were represented from previous literature. Furthermore, time posed a great limitation on this study as the convergent procedure has only been performed for two years in the Lehigh Valley Hospital. Many patients underwent their CP less than a year before the conduction of study. Thus, limited follow-up data was available.

Conclusions

This retrospective review of a cohort of 31 patients suggests that the use of a cyro-balloon catheter for endocardial ablation during the convergent procedure is a viable method to eliminate the recurrence of persistent atrial fibrillation and arrhythmias.

A literature review of radiofrequency ablation convergent procedures offers success rates very close to the cryo-balloon rates described in this study. However, these studies contained a much larger sample size and occurred over a significantly longer time period. For this reason,

further study is warranted that obtains a larger sample size of CP patients and allows more time for follow-up data collection.

Other data should be collected on the time efficiency of the cryo-balloon versus radiofrequency technique. Because the RF catheter requires the electrophysiologist to administer more than 28 burns around the circumferences of each pulmonary vein, while the heart is beating, while the patient is breathing, it is difficult to ensure proper contact of catheter to tissue and to ensure equal distance between each burn so that the entirety of the tissue is electrically isolated. In comparsion, once a cryo-balloon is positioned in the opening of a pulmonary vein and occlusion is confirmed, it is inflated with liquid nitrogen one to three times. The use of a cryo-balloon catheter is simpler, faster and usually ensures complete electrical isolation with no missed tissue.

The efficiency of the procedure can lead to more patients scheduled for operation, and better outcomes with greater quality of life overall.

Additionally, lesser recurrence of arrhythmias correlates with lower costs for the patient and hospital. The more effective the convergent procedure, the lower amount of repeat ablations, cardioversions and medication required.


References

1. JR Edgerton , et al. (2008). Minimally invasive pulmonary vein isolation and partial autonomic denervation for surgical treatment of atrial fibrillation. The Annals of Thoracic Surgery, 86, Vol 1, 35-39.

2. M Zembala, et al. (2012). Minimally invasive hybrid ablation procedure for the treatment of persistent atrial fibrillation: one year results. Kardiologia Polska; 70, 8: 819–828

3. Gehi et al. (2013). Hybrid epicardial-endocardial ablation using a pericardioscopic technique for the treatment of atrial fibrillation. The Heart Rhythm Society, 10, No 1, 22-28.

4. Mayo Foundation (2015). Atrial Fibrillation. Mayo Foundation for Medical Education and Research. Retrieved from http://www.mayoclinic.org/diseases-conditions/atrial-fibrillation/basics/definition/CON-20027014

6. Medtronic (2014). Arctic Front Advance Cardiac CryoAblation Catheter. Medtronic. Retrieved from http://www.medtronic.com/for-healthcare-professionals/products-therapies/cardiac rhythm/ablation-products-for-atrial-fibrillation/arctic-front/index.htm

7.Civello, K.C., Smith C.A., Boedefeld W. (2013). Combined Endocardial and Epicardial Ablation for Symptomatic Atrial Fibrillation: Single Center Experience in 100+ Consecutive Patients Journal of Innovations in Cardiac Rhythm Management, 000, 1-7.

8. FDM. Left Atrial Ablation for Atrial Fibrillation. Digital image. Catheter Ablation

Atrial Fibrillation Ablation. The London Arrhythmia Centre, 2005. Web. 28 July 2015. .

9. O’Neill, L., Hensey, M., Nolan, W., & Keane, D. (2015). Clinical outcome when left atrial posterior wall box isolation is included as a catheter ablation strategy in patients with persistent atrial fibrillation. Journal of Interventional Cardiac Electrophysiology, 1-8.

10. St. Jude Medical (2014). Ensite Velocity Cardiac Mapping System. Web. 28 July 2015.

11. Weheartit.com. Cryoballoon Ablation Catheter. Digital image. Anatomy. Web. 28 July 2015.

Department(s)

Department of Medicine, Cardiology Division, Department of Surgery, Department of Surgery Faculty, Research Scholars (Acknowledgements and Co-authored Publications), Research Scholars - Posters

Awards

Best Overall - Second Place

Best research Project - Third Place

Best Presentation - Second Place

Document Type

Poster

Additional Files
Mattiola Rosalie - Manuscript.pdf (524 kB)
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