Volume 14 – Issue 5 – May 2014 Posted on: 4/23/14 0 Comments 979 reads
Start Page: 27
End page: 29
Interview by Jodie Elrod

In this feature interview we learn more about the multicenter CONVERGE Study, nContact’s randomized IDE Study for the treatment of persistent atrial fibrillation (AF) through a multidisciplinary closed-chest approach. The CONVERGE Study will randomize patients 2:1 between nContact’s epicardial-endocardial Convergent Procedure using the EPi-Sense™-AF guided Coagulation System with VisiTrax® and standalone endocardial ablation using fluid-irrigated catheters.

Here EP Lab Digest® speaks with physicians from the first two sites to enroll patients in theCONVERGE Study: John R. Onufer, MD of Virginia Cardiovascular Specialists, Levinson Heart Hospital in Richmond, Virginia, and Graham Bundy, MD of Cardiothoracic Surgical Associates, Levinson Heart Hospital in Richmond; and David R. Tschopp, MD of Austin Heart in Austin, Texas, and Faraz Kerendi, MD of Cardiothoracic and Vascular Surgeons in Austin.

Please tell us briefly about the CONVERGE IDE Clinical Trial.

Tschopp: The CONVERGE Study is designed to compare standard endocardial ablation to a combined epicardial-endocardial ablation in patients with longstanding persistent AF.

Bundy: This is a randomized study comparing catheter-based treatment with an epicardial and endocardial ablation strategy to treat atrial fibrillation.

Onufer: The purpose is to find the best approach with the most durable results to restore normal rhythm in patients with persistent AF over seven days. This is a large population of patients that tend to be highly symptomatic. We’ve been doing the hybrid procedure with the nContact device for about four or five years now, and have noted that our results have been quite good in terms of managing patients and only requiring one procedure. Therefore, this needed to be looked at in a much more systematic way to confirm that this wasn’t just our patient selection or the way we uniquely did the procedure, but instead was applicable to everyone. The goal is to determine whether this is a better first-time procedure than catheter ablation in these patients.

What are some of the eligibility criteria for the CONVERGE Study?

Tschopp: Patients have to be greater than 18 years of age and less than 80, they have to have had AF for less than 10 years, be refractory or intolerant to at least one antiarrhythmic drug (class I and/or III), and have documented persistent AF.

Onufer: Eligible patients need documentation of persistent AF, their ejection fraction has to begreater than 40 percent, and have no valvular heart disease. They have to have failed an antiarrhythmic drug and be willing to be a candidate for either catheter ablation or a combined catheter and surgical ablation.

Are there patients who are ineligible to participate?

Tschopp: Patients who are ineligible include those who previously had open-heart surgery or left atrial ablations. Patients with paroxysmal AF and patients who are contraindicated for anticoagulants are also excluded.

Kerendi: Patients with a low left ventricular ejection fraction are also excluded.

Please tell us how the CONVERGE Study’s treatment — the epicardial-endocardial Convergent Procedure — is performed.

Kerendi: The epicardial portion is done through a transabdominal, transdiaphragmatic approach, in which we make a small incision in the central portion of the diaphragm and then put in a pericardioscope. We visualize the epicardial surface of the left atrium and pulmonary veins, and do as much of the ablation from the external aspect of the atrium that we can. We’re limited by where the pericardium is actually adhered to those structures, so we cannot do the entire area that we would want to. This is where the endocardial part comes in — to finish off the areas that we’re unable to get to.

Tschopp: From the endocardial perspective, regardless of whether or not you’re doing a Convergent Procedure, you always isolate the pulmonary veins; in longstanding persistent AF patients, many if not most physicians will isolate the posterior wall. In addition to that, physicians will frequently do a cavotricuspid isthmus ablation line. When you’re doing a ConvergentProcedure, since the surgeon has already done an epicardial ablation, the posterior wall is pretty much isolated. Therefore, you only need to focus on completing the isolation of the pulmonary veins, which primarily involves ablation over the areas of pericardial reflection that aren’t adequately ablated by the epicardial approach, and then completing the cavotricuspid isthmus ablation.

Bundy: The procedure starts with the patient undergoing a fairly excessive cardiac screening including possible cardiac catheterization and TEE, as well as a thorough history and physical exam, so by the time they get to the operating room, we’re confident they’re good candidates for the procedure. I begin with a 2 cm subxiphoid incision, an abdominal incision just below the xiphoid process in the midline, then insufflate the abdomen with carbon dioxide and place two 5 mm ports in the left and right upper quadrants. Next we retract the liver caudally and make a small left 2 cm incision transversally in the central tendon of the diaphragm. Then I use a large hollow cannula to gain access in the pericardial space. Through that cannula, I can advance my catheter, which has a 3 cm ablation coil and is approximately 1 cm wide. It is an irrigated system with vacuum assistance to facilitate contact with the epicardial surface. It provides a fairly large area of ablation during a 90-second ablation. I focus on ablating the entire posterior left atrium between the pulmonary veins, ablate within the oblique sinus, anterior to the left-sided pulmonary veins and advance the catheter toward the ligament of Marshall. Then I advance the cannula over the inferior vena cava and ablate the veins anteriorly on the right side — the superior veins and inferior veins — and ablate down into the oblique sinus. What I cannot access epicardially, Dr. Onufer and his associates can get to endocardially. When I’m finished with the epicardial portion of the procedure, which takes about an hour and a half to two hours, I leave a drain in the pericardial space, and close the diaphragm and abdominal incisions. Then Dr. Onufer or one of his associates will come in and perform electrophysiologic mapping and ablation.

Onufer: After his completion of the epicardial approach, we place catheters exactly like we would for any AF ablation; this includes placing a coronary sinus catheter, an intracardiac ultrasound catheter to visualize the transseptal and monitor for any complications, and either a lasso or spiral catheter and an irrigated tip catheter are placed into the left atrium along with a His catheter. We’ll also create a voltage map of the left atrium beforehand to see 3D geometry and identify any gaps. Then we ablate to complete the pulmonary vein isolation. Upon completion of this, we typically see a marked reduction of voltage in the posterior left atrium. However, everyone has needed some type of additional lesions around their pulmonary veins to get complete isolation. The nContact lesion set does not completely isolate the pulmonary veins, which we don’t look at as any detriment, it’s just part of the synergistic or combined effect we’re trying to achieve with doing both procedures. So after doing pulmonary vein isolation and confirming block, we’ll typically challenge with isoproterenol and programmed stimulation. If we induce any atrial flutters or atrial tachycardias, we’ll eliminate those. After this, the catheters are withdrawn and the patient is sent to the ICU under full anticoagulation with coumadin. They are monitored in the ICU for about two days, and usually go home after the second day. The pericardial drain placed by the surgeon is usually taken out the day after the procedure, or within the first postoperative day.

The Convergent Procedure is a hybrid procedure; how does it differ from other hybrid ablations? Does it require a new room or new equipment?

Onufer: In terms of other hybrid ablations, the procedure is staged into two separate procedures so the surgeon performs isolation of each of the pulmonary veins in one setting, and then the patient comes back in a second setting for the endocardial ablation. It’s interventionally very different and requires thoracoscopic access. That being said, the Convergent Procedure is done in a single procedure setting. There is usually less pain and earlier discharge with epicardial ablation from the subxiphoid approach. In terms of the facility needed, we use a hybrid room, which means that the EP lab is completely conducive to the surgeon bringing in their equipment for the procedure. The room is set up for OR capability and is larger to accommodate surgical equipment.

Kerendi: Other hybrid ablation approaches require either a thoracotomy or thoracoscopy via a 3 or 4 port approach. The only other hybrid procedure that’s commonly performed involves the bilateral thoracoscopic approach. First, to access the pulmonary veins and the atrium on the right side, and then do a similar approach on the left side; this makes a total of 6-8 incisions and takes longer to accomplish compared to what we do. With the Convergent Procedure there are only two incisions made in the abdomen, which is better from a pain standpoint. From a case duration standpoint, the Convergent Procedure is much shorter than any other approach out there.

Tschopp: I believe there are actually two available hybrid procedures other than the Convergent Procedure, but both require thoracoscopy. The Convergent Procedure is the least invasive epicardial approach to successfully isolate the posterior wall, so that is a significant advantage, especially when it’s coupled with a reduced morbidity.

Kerendi: It also has the advantage of ablating on the surface of the heart and ganglionated plexi, which are thought to be important contributors to AF.