Advances in Balloon Technologies for AF Ablation
Dr. Karl-Heinz Kuck presented new advances in balloon technologies for AF ablation at AF2107.
Electrical isolation of the pulmonary veins is the ‘cornerstone’ approach to treat symptomatic atrial fibrillation (AF) by catheter ablation.1,2 Traditionally, pulmonary vein isolation (PVI) has been achieved by circumferential heating of the left atrial tissue surrounding the pulmonary veins in a serial, ‘point- by-point’ application of focal radiofrequency current (RFC) lesions utilizing irrigated electrode catheters and electroanatomical guidance. In his session on Friday, Karl-Heinz Kuck, MD (Asklepios Klinik St. Georg, Hamburg, Germany) explored new advances in balloon technologies for AF ablation, including the cryoballoon, endoscopic PVI, and the Apama® RF balloon.
“An apparently more straight-forward approach to PVI is that of placing a special cryoballoon catheter under fluoroscopic guidance at the pulmonary vein antra and delivering coolant to the inside of the balloon, thereby freezing the atrial tissue in contact with the balloon in a single-shot approach lasting a few minutes,” said Dr. Kuck. “The initially available cryoballoon (Medtronic) enabled tissue freezing only along its equator, whereas in the currently available, second-generation cryoballoon, the entire distal hemisphere of the balloon is cooled down to sub-zero temperatures.”
Both generations of the cryoballoon were tested for efficacy in the treatment of drug-refractory paroxysmal AF against RFC catheters with and without contact-force sensing (Biosense Webster, Inc.) in the randomized, multicenter FIRE AND ICE trial. The trial confirmed its hypothesis of noninferiority, in terms of time to first documented clinical failure within one year outside a 90-day blanking period, of the cryoballoon vs RFC ablation in 374 patients undergoing the former and 376 patients undergoing the latter treatment modality.3 Clinical failures assessed in this primary efficacy endpoint of the trial included the recurrence of AF (lasting for more than 30 sec), atrial flutter or atrial tachycardia, the prescription of class I or III antiarrhythmic agents, and repeat ablation. Primary efficacy rates (Kaplan-Meier estimates) were 34.6% for cryoballoon ablation and 35.9% for RFC ablation, corresponding to a hazard ratio of 0.96 (P=0.0004 for noninferiority; Figure 1).
The primary safety endpoint of FIRE AND ICE — a composite of all-cause death, all- cause stroke/transient ischemic attack, arrhythmia-related and non-arrhythmia-related serious adverse events — was also not found to be different between the study groups at 1 year, with estimated event rates of 10.2% in the cryoballoon group and 12.8% in the RFC group (hazard ratio 0.78; P=0.24).3 Methodology-specific differences were observed for the duration of the ablation procedure, which was on average significantly shorter for cryoballoon ablation (124 vs. 141 minutes for RFC ablation; P<0.0001), and for fluoroscopy time, which was on average significantly longer for cryoballoon ablation (22 vs. 17 minutes; P<0.0001).
He continued: “With respect to rehospitalization events during a mean follow-up of 1.5 ± 0.8 years, patients undergoing cryoballoon ablation fared significantly better than patients undergoing RFC ablation. The former experienced fewer rehospitalizations for any cause (32.6% vs. 41.5%; P=0.01) as well as for cardiovascular reasons (23.8% vs. 35.9%; P<0.01), and had to undergo less often repeat ablation (11.8% vs. 17.6%; P=0.03) or DC cardioversion procedures (3.2% vs. 6.4%; P=0.04).4 The reduction in rehospitalizations, mainly for cardiovascular reasons and repeat ablations, led to significantly lower costs for health-care payers in patients undergoing cryoballoon ablation. Quality of life (both mental and physical) improved, regardless of the ablation modality within the first 6 months of the index ablation. That improvement was maintained throughout the study out to the 30-month visit.”
Endoscopic Pulmonary Vein Isolation
“The endoscopic ablation system (EAS; Figure 2) is a balloon-based ablation device consisting of a compliant balloon that can be adapted to the individual pulmonary vein size (maximum diameter 35mm),” explained Dr. Kuck. “The central balloon shaft houses a laser energy source, which can be titrated from 5.5W to 12W, and a 2F endoscope.”
The rate of acute PVI applying the EAS is reported with 98% to 100%,5-7 and is translated into an 86% PVI durability at invasive re-assessment after 3 months.6 Direct comparison of PVI using the EAS vs. standard RFC ablation in a prospective, multicenter, randomized study of 353 patients with paroxysmal AF proved the noninferiority of endoscopic ablation with regard to efficacy (61.1% vs. 61.7%; P=0.003) and primary adverse event rate (11.8% vs. 14.5%; P=0.002).8
The Apama RF Balloon
The Apama® RF balloon (Apama Medical, Inc.) is a new RFC ablation catheter that combines balloon efficiency with single-point RFC versatility (Figure 3). It consists of an anterior and lateral row of flat, irrigated electrodes. Multipoint RFC application allows for single-shot, customizable ablation geometries. Since the balloon is flat, not only can it be used for PVI, but it can be used for focal ablation and for linear or circular lesions within the atria as well. Four built-in cameras enable real-time visualization to assess electrode contact sites with blood contamination.
He added: “A first-in-human study was initiated earlier this year at 4 international sites, which enrolled 18 patients with both paroxysmal and persistent AF. The data show successful electrical isolation in 98% of all pulmonary veins, with average procedure and balloon times of 2.4 and 1.4 hours, respectively. All safety end-points were reached.”
What is the take-home message? “A variety of balloon-based catheter ablation systems are currently being developed to overcome the limitations of PVI by way of serial point-by-point RFC application,” said Dr. Kuck.
Haissaguerre M, Jais P, Shah DC, et al. Spontaneous initiation of atrial fibrillation by ectopic beats originating in the pulmonary veins. N Engl J Med. 1998;339:659-666.
Verma A, Jiang C, Betts TR, et al. Approaches to catheter ablation for persistent atrial fibrillation. N Engl J Med. 2015;372:1812-1822.
Kuck KH, Brugada J, Fürnkranz A, et al. Cryoballoon or Radiofrequency Ablation for Paroxysmal Atrial Fibrillation. N Engl J Med. 2016;374:2235-2245.
Kuck KH, Fürnkranz A, Chun KR, et al. Cryoballoon or radiofrequency ablation for symptomatic paroxysmal atrial fibrillation: reintervention, rehospitalization, and quality-of-life outcomes in the FIRE AND ICE trial. Eur Heart J. 2016 Jul 5 [Epub ahead of print].
Schmidt B, Metzner A, Chun KR, et al. Feasibility of circumferential pulmonary vein isolation using a novel endoscopic ablation system. Circ Arrhythm Electro-physiol. 2010;3:481-488.
Dukkipati SR, Neuzil P, Kautzner J, et al. The durability of pulmonary vein isolation using the visually guided laser balloon catheter: Multicenter results of pulmonary vein remapping studies. Heart Rhythm. 2012;9:919-925.
Metzner A,Wissner E, Schmidt B, et al. Acute and long-term clinical outcome after endoscopic pulmonary vein isolation: results from the first prospective, multicenter study. J Cardiovasc Electro-physiol. 2013;24:7-13.
Dukkipati SR, Cuoco F, Kutinsky I, et al.; HeartLight Study Investigators. Pulmonary Vein Isolation Using the Visually Guided Laser Balloon: A Prospective, Multicenter, and Randomized Comparison to Standard Radiofrequency Ablation. J Am Coll Cardiol. 2015;66:1350-1360.