EP Lab Digest - October 2007 - (Page 26)

26 CRYOTHERAPY UPDATE OCTOBER 2007 The Sustained Treatment of Paroxysmal Atrial Fibrillation (STOP AF) Clinical Trial: Interview with Kevin Wheelan, MD Interview by Jodie Elrod disease.The age range is 18-75 years old, and these patients have to have failed at least 1 primary antiarrhythmic drug in the past (see website for details of inclusion/exclusion criteria). What advantages does the Arctic Front balloon offer over current treatments for AF? Currently there are some surgical and catheter-based options that are clinically available for patients. Of the catheterbased strategies, the primary approach that is being used worldwide is radiofrequency energy. There is a wide range of catheters; most physicians who do this procedure use either an 8 mm tip or an irrigated tip 4 mm catheter to ablate in the left atrium.The cryocatheter, a steerable EP catheter with a defined tip electrode for cryoablation purposes, is most commonly used in the 6 mm or 8 mm size.With cryoablation you have the ability to spot freeze, and this can be especially helpful in AVNRT cases; however, when it comes to treating atrial fibrillation, point-by-point freezing is really not being used as a primary modality, because it takes too long. The advantage in using the cryoballoon is that it allows you to create an entire circumferential freeze with 1 application that lasts 4 minutes. There are other research protocols taking place. One is a high intensity ultrasound catheter that is designed to disrupt tissue by beaming high energy ultrasound signals into the targeted zone of tissue and destroying them, but that trial’s technology has been met with some problems and is moving forward slowly. More recently, another trial has gotten underway using a laser-based approach to target the application of energy at the mouth of the pulmonary veins to create ablative lesions. This trial is still at an early stage. Tell us about the Arctic Front® balloon, including size options, diameter, FlexCath interoperability, etc. The Arctic Front cryoballoon (CryoCath Technologies, Inc., Montreal, Quebec, Canada), as it is currently configured, is available in 2 sizes: 23 mm and 28 mm with an inner lumen for wire manipulation. It is predominantly a spherical design balloon, with an added safety feature in that there is an inner balloon and an outer balloon. The outer balloon maintains a constant vacuum, so in the event that any leaks should occur, none of the liquid Nitrous Oxide would come in contact with the patient. The delivery system includes a 14 French steerable sheath, and from my experience, the steerable balloon platform is well designed and very robust to maneuver in the left atrium and occlude the pulmonary veins. I am also impressed by its effectiveness in isolating the targeted pulmonary veins. I n this article, we speak with Dr. Kevin Wheelan, one of the investigators of the STOP AF clinical trial. Dr. Wheelan is Chief of Staff at Baylor Heart and Vascular Hospital in Dallas, Texas. etc. Most importantly, the primary goal of the trial is to statistically prove that the catheter cryoablation technique is as safe as medication, but offers improved efficacy. What is the purpose of the STOP AF trial? Describe the trial objectives. What is important about STOP AF is that it is the first trial designed to obtain FDA approval for a catheter-based treatment for atrial fibrillation. Although the area of AF ablation has grown tremendously over the past 5 or 6 years, all of it has been based on radiofrequency catheter ablation, which has evolved from treatment of many other types of arrhythmias. None of the catheters that we currently use are actually approved for atrial fibrillation ablation by the FDA; they are used off label. This is a pivotal trial in that it is the first time that the FDA has dealt with the issue of defining the success of catheter-based ablation approaches to atrial fibrillation. STOP AF has a rigorous “all or none” endpoint of any documented AF as a failure in either the medical or balloon treatment arms. The objective of the trial is to prove that cryoablation of the PV ostium is better than medical therapy in patients with idiopathic paroxysmal atrial fibrillation. The endpoint of the study is the elimination of spontaneous AF at one year. The secondary endpoints of the trial are symptomatic improvement, reduction in frequency of the episodes, differences in incidence of hospitalizations or need for cardioversion, How does the Arctic Front balloon treat atrial fibrillation? What unmet need will the Arctic Front balloon help fulfill? The goal of this trial is to create complete isolation of all 4 of the pulmonary veins (or their branches). However, as we know, sometimes the right side (more often than the left) of the veins may have a middle vein, so you might have 3 different discreet vein ostia there. In order to be classified as successful according to the protocol, we must isolate at least 3 of the pulmonary veins (2 superiors and 1 inferior). Patients receive a CT, angiography or MRI scan ahead of time, which defines their pulmonary venous anatomy. During the procedure, we’ll use intracardiac echo, angiography, and the CT scan or MRI to determine optimal sizing of which balloon we want to use. More commonly we have been using the larger size balloon and reserving the smaller balloon only for those veins that cannot be isolated with the 28 mm balloon.We are finding that by being more proximal in what we would call the ‘vein antrum,’ rather than inside the actual os of the vein, we are getting a larger surface area of freeze, and I believe a better degree of isolation and elimination of the substrate that is causing AF in this population of patients. What is the target patient population for the study? How many sites are participating? There are a total of 22 North American sites. STOP AF is a randomized controlled trial, with a 2:1 randomization; this means that 2 patients will receive cryoablation and 1 patient will receive medication.This design is predicated on statistical modeling designed to prove or disprove the study hypothesis that ablation is equal to or better than medication for prevention of AF. The medication (or control) group will receive 1 of 3 different antiarrhythmic drugs — flecainide, propafenone or sotalol. The study design is for a total of 243 patients, with 12 months of follow up. There is also the opportunity of crossover from the drugs to the cryo treatment arm at 6 months. The specific target population is patients with idiopathic paroxysmal atrial fibrillation, defined as 2 or more episodes of AF during the 2 months preceding enrollment, at least 1 of which must be documented by EKG. Patients are only allowed mild structural heart How will this technology impact both AF patients and the physicians who treat them? I believe this is highly dependent on what the results of this study are. Currently this technology is marketapproved in Europe, and if one looks at the rate of adoption and the growth occurring among our European colleagues, I predict there will be a very significant and rapid adoption of this technology in the United States. This is all contingent upon the results of this trial proving to be positive. The European data which has been presented indicates that there is at least an 80% effectiveness rate with cryoablation for this subgroup of paroxysmal AF patients, and there has also been some recent abstract data suggesting it may have a role in persistent AF patients as well. If the U.S. trial comes to the same conclusions as the European data, I personally think there will be a radical paradigm shift in the electrophysiology lab,

Table of Contents Feed for the Digital Edition of EP Lab Digest - October 2007

Finally! The New Registered Cardiac Electrophysiology Specialist (RCES) Credential: Interview with Christopher M. Nelson, RN, RCIS, FSICP ECG 101: Closing the Gap Phenomenon Contents Letter from the Editor ICD Patient Support Group: St. Peter’s Hospital Spotlight Interview: Community Healthcare System Use of Magnetic Catheter Navigation for Ablation of Focal Tachycardias Echocardiography: The Preeminent Front Line Screening and Diagnostic Tool for Cardiovascular Imaging and Physiological Assessment First Annual EP Lab Digest Salary Survey: Last Chance! Clinical Trial Update: 2007 Email Discussion Group Adopting and Implementing the AF Ablation Consensus Statement Electrophysiology in the West Summit Events Calendar The Sustained Treatment of Paroxysmal Atrial Fibrillation (STOP AF) Clinical Trial: Interview with Kevin Wheelan, MD Industry News and Products

EP Lab Digest - October 2007

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