Steps for Performing the Convergent Procedure: Experience at Mission Hospital

Significant strides have been made in catheter ablation of atrial fibrillation. For paroxysmal atrial fibrillation (PAF), pulmonary vein isolation using radiofrequency or cryoablation has a success rate as high as 85% at 1 year.¹ Recurrences can be due to pulmonary vein reconnection, extrapulmonary vein triggers, comorbidities that contribute to AF, or all of the above. That being said, the majority of patients with PAF tend to have similar electroanatomic characteristics and mechanisms, which is why pulmonary vein isolation is effective. These are largely the reasons why the design and implantation of new technology clinical trials is relatively straightforward. 

Persistent atrial fibrillation represents a much greater challenge due to its electroanatomic heterogeneity in patients. Within the persistent atrial fibrillation population, there is variability in scar burden, scar location, degrees of left atrial enlargement, and associated comorbidities. All of these impact the mechanisms of atrial fibrillation, and have implications in choice of ablation techniques and technologies. Even within a given patient, multiple mechanisms (such as drivers or rotors) can coexist. This heterogeneity has led to the development of a variety of mapping technologies and ablation techniques. Furthermore, there is a significant lack of consensus among electrophysiologists on the optimal approach to persistent atrial fibrillation.² As a result, it is challenging to design and implement randomized controlled clinical trials for persistent atrial fibrillation ablation. For these reasons, treatment must be individualized, and there are multiple tools available.³ 

There is increasing evidence that the left atrial posterior wall is a critical part of initiating and maintaining persistent atrial fibrillation. Endocardial ablation of the posterior wall is limited by the proximity to the esophagus, often resulting in incomplete posterior wall isolation. Epicardial ablation is limited by its more invasive nature, and high-density mapping pre and post ablation is often not performed.⁴ Technologies have been developed to create hybrid procedures employing both approaches to ensure comprehensive voltage mapping and durable transmurality of lesions. 

Convergent is a newer hybrid atrial fibrillation ablation procedure in which the surgeon via subxiphoid access performs a posterior wall lesion set.⁵ Then, a cardiac electrophysiologist maps and completes isolation of the pulmonary veins and posterior wall. A cavotricuspid isthmus (CTI) ablation line is often performed to prevent right atrial flutter. There are two targeted patient groups for Convergent ablation: longstanding persistent atrial fibrillation (>1 year) and persistent atrial fibrillation with recurrence after failed endocardial ablation. The procedure can be done as a same-day or staged procedure (6-8 weeks separation). With a same-day procedure, the patient requires one hospitalization and one time under anesthesia; however, the procedure is longer (typically 5-6 hours). With a staged approach, the epicardial lesions have time to heal and scar, which may limit the need for extensive ablation after endocardial mapping.

Mission Hospital is the first institution on the West Coast to perform the Convergent procedure for atrial fibrillation. This case is presented below. 

CASE DESCRIPTION

The patient is a 75-year-old male with a 5-year history of longstanding persistent atrial fibrillation. He failed multiple cardioversions as well as rhythm control treatment with amiodarone and sotalol. He remained symptomatic with fatigue, limiting his quality of life. The patient underwent the Convergent procedure using a staged approach. At the end of epicardial ablation, the patient was cardioverted to sinus rhythm (Figures 1-3, Video 1). Atrial fibrillation recurred within 2 days, and he was loaded with amiodarone. Six weeks later, he underwent endocardial mapping and ablation, including completion of pulmonary vein and posterior wall isolation (Figures 4 and 5, Video 2). After left atrial ablation, the patient transitioned to right atrial CTI-dependent flutter, which converted to sinus rhythm after CTI ablation (Figures 6-8). Since the ablation, he has been in sinus rhythm for over a year. 

DISCUSSION

Our steps for performing the Convergent procedure are as follows (Convergent approach subxiphoid animation is also available at https://bit.ly/2p9bILe).

Epicardial ablation (Figures 9 and 10):

• Identify xiphoid process.
• Create pericardial window below xiphoid process to allow access to posterior left atrium.
• Surgeon may remove xiphoid process for easier access.
• The pericardial window is created just above the bifurcation of the pericardium and diaphragm to give a shallow angle for access to the posterior left atrium. The shallow angle is important for both safety and efficacy.
• A cannula is inserted through the window and these structures are visualized: inferior vena cava, right inferior pulmonary vein, left inferior pulmonary vein, and left superior pulmonary vein. The superior veins may not always be visual. Getting the cannula as superior as possible along the posterior wall will help visualization. 
• The ablation catheter (EPi-Sense Coagulation Device, AtriCure, Inc.) is advanced through the cannula, and a set of linear lines is performed from distal to proximal along as much of the posterior left atrium as possible. Deflection off the pericardium should occur as high/superior as possible. Lesions start from right pulmonary veins to left pulmonary veins.
• It is important to visually confirm that the lesions intersect, and utilize the electrogram-sensing function of the catheter to confirm electrical isolation of the posterior wall.
• The cannula and catheter are removed and incisions are closed.

Endocardial ablation:

• Femoral venous access is gained with transseptal catheterization.
• Three-dimensional mapping of the left atrium and pulmonary veins is performed. 
• Pulmonary vein isolation is completed.
• Posterior wall isolation is completed.
• Right atrial cavotricuspid isthmus flutter line is performed.

At Mission Hospital, it was determined that adjuvant use of antiarrhythmic medication (e.g., amiodarone or dofetilide) with Convergent ablation results in the best chance of sinus rhythm in patients with longstanding persistent atrial fibrillation. This observation is supported by the findings of other investigators.⁶ 

CONCLUSION

Ablation of persistent atrial fibrillation remains a work in progress. Treatment must be individualized for the patient by creating a tool box of mapping technologies and ablation techniques. The latest addition to this is the Convergent procedure, which uses a hybrid technology and approach that is less invasive than prior hybrid strategies. Although larger studies are needed, initial data appears very promising. The treatment of comorbidities including obesity, diabetes, hypertension, and sleep apnea is also an important and often overlooked part of the atrial fibrillation treatment program.⁷ 

Acknowledgements.

Dr. Desai wishes to acknowledge the following from Mission Hospital who are a part of the Atrial Fibrillation treatment program: Drs. Lynne Hung, Jay Tiongson, Sevak Darbinian, and Taylor Tang, as well as the Mission Hospital Cardiac Cath Lab and Operating Room staff.

Disclosure: The author has no conflicts of interest to report regarding the content herein.

References

1. Kuck KH, Brugada J, Furnkranz A, et al. Cryoballoon or radiofrequency ablation for paroxysmal atrial fibrillation. N Engl J Med. 2016;374:2235-2245.
2. Sommer P, Kircher S, Rolf S, et al. Successful Repeat Catheter Ablation of Recurrent Longstanding Persistent Atrial Fibrillation with Rotor Elimination as the Procedural Endpoint: A Case Series. J Cardiovasc Electrophysiol. 2016;27:274-280.
3. Verma A, Jiang CY, Betts TR, et al. Approaches to catheter ablation for persistent atrial fibrillation. N Engl J Med. 2015;372:1812-1822.
4. Kumar P, Bamimore A, Schwartz J. Challenges and Outcomes of Posterior Wall Isolation for Ablation of Atrial Fibrillation. J Am Heart Assoc. 2016;5(9).
5. AFib treatment. AtriCure. Available online at https://www.atricure.com/atrial-fibrillation-treatment. Accessed March 12, 2018.
6. Khan A, Mittal S, Kamath GS, et al. Pulmonary vein isolation alone in patients with persistent atrial fibrillation: an ablation strategy facilitated by antiarrhythmic induced reverse remodeling. J Cardiovasc Electrophysiol. 2011;22:142-148.
7. Lau D, Nattel S, Kalman J, et al. Modifiable Risk Factors and Atrial Fibrillation. Circulation. 2017;136:583-596.