Catheter ablation for the treatment of paroxysmal atrial fibrillation (PAF) is recommended in patients who are intolerant or refractory to Class I or III antiarrhythmic drug therapy.1 Pulmonary vein isolation (PVI) is the cornerstone of the ablation procedure and can be achieved using a variety of technologies and energy sources. In addition to conventional radiofrequency catheter ablation and cryoballoon ablation, the latest technology to receive FDA premarket approval for PVI was the visually guided laser balloon (VGLB, HeartLight Endoscopic Ablation System, CardioFocus) in 2016 (Figure 1). The VGLB allows point-by-point ablation around each pulmonary vein (PV) under direct visual guidance with similar one-year success rates than conventional PVI.2
A 56-year-old male with a history of paroxysmal atrial fibrillation (PAF) refractory to antiarrhythmic drug therapy was referred to the University of Illinois at Chicago Medical Center for PVI. After discussing the available treatment modalities, the patient opted for PVI using the VGLB.
The procedure was performed under general anesthesia in the electrophysiology laboratory. Vascular access was obtained, and double transseptal puncture was performed under fluoroscopic and intracardiac echocardiography guidance using a standard needle and transseptal sheaths. Intravenous heparin was administered to maintain an activated clotting time ≥300 seconds. One transseptal sheath was exchanged over-the-wire for a 12 French steerable transseptal VGLB sheath. The deflated VGLB was advanced into the left atrium and positioned in the target PV. A circular mapping catheter was advanced through the standard transseptal sheath and used to record PV activity before and after VGLB ablation. Esophageal temperature monitoring was performed during energy delivery using a temperature cut-off of 39°C.
The VGBL was inflated and positioned at the proximal PV ostium. Under direct visual guidance, point-by-point laser ablation was performed deploying an overlapping, contiguous lesion set encircling the target PV ostium (Figure 2). Electrical isolation was verified after balloon deflation using the circular mapping catheter. All PVs were targeted in identical fashion until electrical PVI was achieved. The number of laser applications per PV was in the range of 28 to 34. During ablation of the right PVs, phrenic nerve pacing was performed at maximum output and the right phrenic nerve compound motor action potential (CMAP) was monitored. No change in right phrenic nerve function was noted during or after the procedure, and no other complications occurred.
Following a 30-minute waiting period and after verifying persistent PVI, the procedure was terminated, and all catheters and sheaths were removed. Hemostasis was accomplished with manual compression. The patient was extubated and returned to a monitored bed in stable condition, having tolerated the procedure well. Two months following the procedure, he is doing well without evidence of recurrent atrial fibrillation.
Overview of the HeartLight Endoscopic Ablation System
The first prospective multicenter study on the use of the VGLB in patients with PAF was published in 2009.3 Of 116 targeted PVs, 105 (91%) were acutely isolated, resulting in a one-year freedom from recurrent atrial fibrillation of 60%. The study used three different fixed balloon sizes. In its current iteration, the HeartLight Endoscopic Ablation System incorporates a compliant balloon with a maximum diameter of 35 mm. The balloon is filled and continuously flushed with heavy water (deuterium oxide, D2O), which allows stepwise adaptation of balloon size adjustable to the individual PV anatomy. The system is introduced and maneuvered via a 12F steerable transseptal sheath. The catheter shaft incorporates a 2F (0.0262-inch) fiber-optic endoscope providing the operator with a direct view of the PV antrum once the balloon is positioned and inflated. In addition, the catheter shaft houses a 980 nm laser diode delivering a 20- or 30-second burst of laser energy. A single ablation lesion covers a 30° arc. In order to achieve a contiguous lesion set around each PV ostium, individual lesions should overlap by 30-50%. Laser energy can be titrated from 5.5 Watts to 12 Watts depending on left atrial wall thickness and nearby extracardiac structures (e.g., esophagus). Rotating, advancing or retracting the laser beam allows for an individualized point-by-point lesion design. Intracardiac echocardiography, fluoroscopy, and/or selective PV venography may aid maneuvering the VGLB to the individual PV ostium. Electrical PV activity is recorded before ablation, and isolation is verified after anatomical circumferential ablation by a circular mapping catheter. If PVI is not achieved after initial anatomical circumferential ablation, gap mapping and ablation can be performed with the spiral mapping catheter positioned in the target PV distal to the inflated VGLB. Routine preprocedural imaging using cardiac MRI is not mandatory and had no impact on successful ablation outcome in a study by Metzner et al.4
Applying the Best Ablative Strategy
During conventional circumferential PVI using radiofrequency energy, ipsilateral PVs are isolated in pairs. Wissner et al compared circumferential to individual PVI using the VGLB.5 The greater distance between the right superior and inferior PV ostium limited simultaneous endoscopic visualization and deployment of connecting wide circumferential lesion sets. The study concluded that the preferred ablative strategy should individually target each PV.5 Since laser energy can be applied at various power settings, two studies compared different energy protocols during VGLB-based PVI. Both studies demonstrated superiority of a higher energy protocol, which minimized the need for touch-up lesions following placement of the initial anatomically guided circumferential lesion set.6,7
How to Minimize Complications
To avoid thermal damage, use of an esophageal temperature probe is strongly recommended. The esophageal cut-off temperature is set to 38.5-39.0°C. Metzner et al found a comparable incidence of thermal esophageal lesions on post-procedural esophagogastroscopy following VGLB-based and conventional PVI.8 Right phrenic nerve palsy occurred at a rate of 1.4% in a study enrolling 72 patients from three different centers using fluoroscopic surveillance and tactile feedback during right phrenic nerve pacing from the superior vena cava.9 Recently, the concept of CMAP monitoring was introduced for cryoballoon ablation.10 A reduction in CMAP amplitude of 30-50% during right phrenic nerve pacing heralds impending nerve damage. A decrease in CMAP amplitude precedes a reduction in diaphragmatic excursion and ablation should be stopped. At our institution, we routinely use CMAP monitoring during all balloon-based atrial fibrillation ablation procedures.
Outcome and Outlook
A study by Dukkipati et al demonstrated durable isolation in 61/68 (90%) PVs at three months following the index PVI procedure.11 The HeartLight study, a non-inferiority multicenter, randomized controlled trial, enrolled 353 patients with drug-refractory PAF to PVI using conventional radiofrequency ablation aided by an electroanatomical mapping system or the VGLB.2 In the VGLB group, acute isolation was achieved in 649/664 (97.7%) PVs. The 12-month freedom from recurrent atrial arrhythmias was 63.5% in the VGLB group and 63.9% in the conventional arm (P=0.94). In April 2016, published results led to FDA premarket approval of the HeartLight Endoscopic Ablation System in the U.S. A post-approval registry will collect clinical outcome data on patients in the U.S. treated after commercial approval of the VGLB. Finally, clinical studies are underway in Europe to test the next-generation VGLB (HeartLight Excalibur Balloon, CardioFocus) that promises an even more compliant balloon design and a decrease in time needed to complete the ablation procedure.
Disclosures: Dr. Wissner reports receiving consultant fees from CardioFocus and Medtronic during the conduct of the study.
- Anderson JL, Halperin JL, Albert NM, et al. Management of patients with atrial fibrillation (compilation of 2006 ACCF/AHA/ESC and 2011 ACCF/AHA/HRS recommendations): a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines. J Am Coll Cardiol. 2013;61(18):1935-1944.
- 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(12):1350-1360.
- Reddy VY, Neuzil P, Themistoclakis S, et al. Visually-guided balloon catheter ablation of atrial fibrillation: experimental feasibility and first-in-human multicenter clinical outcome. Circulation. 2009;120:12-20.
- Metzner A, Kivelitz D, Schmidt B, et al. Impact of pulmonary vein anatomy assessed by cardiac magnetic resonance imaging on endoscopic pulmonary vein isolation in consecutive patients. Europace. 2012;14(4):474-480.
- Wissner E, Metzner A, Reissmann B, et al. Wide circumferential versus individual isolation of pulmonary veins using the endoscopic ablation system. J Cardiovasc Electrophysiol. 2014;25(3):253-258.
- Metzner A, Wissner E, Schoonderwoerd B, et al. The influence of varying energy settings on efficacy and safety of endoscopic pulmonary vein isolation. Heart Rhythm. 2012;9(9):1380-1385.
- Bordignon S, Chun KR, Gunawardene M, et al. Energy titration strategies with the endoscopic ablation system: lessons from the high-dose vs. low-dose laser ablation study. Europace. 2013;15(5):685-689.
- Metzner A, Schmidt B, Fuernkranz A, et al. Esophageal temperature change and esophageal thermal lesions after pulmonary vein isolation using the novel endoscopic ablation system. Heart Rhythm. 2011;8(6):815-820.
- 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 Electrophysiol. 2013;24(1):7-13.
- Franceschi F, Koutbi L, Mancini J, Attarian S, Prevôt S, Deharo JC. Novel electromyographic monitoring technique for prevention of right phrenic nerve palsy during cryoballoon ablation. Circ Arrhythm Electrophysiol. 2013;6:1109-1114.
- Dukkipati SR, Neuzil P, Skoda J, et al. Visual balloon-guided point-by-point ablation: reliable, reproducible, and persistent pulmonary vein isolation. Circ Arrhythm Electrophysiol. 2010;3(3):266-273.