Europace Advance Access originally published online on February 13, 2008
Europace 2008 10(3):280-283; doi:10.1093/europace/eun025
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ELECTROPHYSIOLOGY
Successful ablation of focal left atrial tachycardia using Stereotaxis NiobeTM remote magnetic navigation system
1 Division of Cardiac Electrophysiology, Ohio State University Medical Center, Columbus, OH, USA; 2 Division of Cardiac Electrophysiology, University of Texas-Health Science Center at Houston, 6431 Fannin Street, Suite MSB 1.246, Houston, TX 77030, USA
Manuscript submitted 8 October 2007. Accepted after revision 14 January 2008.
* Corresponding author. Tel: +1 713 500 6590; fax: +1 713 500 6556. E-mail address: bkantharia{at}yahoo.com
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Abstract |
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Stereotaxis NiobeTM remote magnetic navigation system (MNS) (St Louise, USA), is a new technology that has applications in the field of catheter based ablation treatment of cardiac arrhythmias. Most if not all data on the feasibility, safety, and efficacy of the Stereotaxis NiobeTM MNS comes from select centres where highly skilled personnel have acquired considerable experience using this technology. Herein, we report a case where the Stereotaxis NiobeTM MNS was successfully used to perform remotely-controlled high density three-dimensional electroanatomical mapping and radiofrequency ablation of a focal atrial tachycardia originating from the anteroseptal region of the left atrium.
Key Words: Magnetic navigation system, Atrial tachycardia, Radiofrequency ablation
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Introduction |
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Stereotaxis NiobeTM remote magnetic navigation system (MNS) (St Louise, USA) technology has applications in the field of catheter based ablation treatment of cardiac arrhythmias.1
–7 However, most if not all data on the feasibility, safety, efficacy, and the advantages of the Stereotaxis NiobeTM MNS technology over the conventional catheter ablation therapy of cardiac arrhythmias come from select high-volume centres where operators have acquired considerable experience using this technology.1–7 One centre has reported an alarming rate of catheter charring and incomplete pulmonary vein isolation using the magnetic navigation catheter.7 We, therefore, believe that further technical development and experience is necessary for wider application of the Stereotaxis NiobeTM MNS for ablation of complex cardiac arrhythmias. Herein, we report our experience where for an elderly man with focal atrial tachycardia originating from the anteroseptal region of the left atrium we used Stereotaxis NiobeTM MNS to perform remotely-controlled high density three-dimensional electroanatomical CARTOTM (Biosense-Webster, USA) mapping and radiofrequency (RF) ablation successfully, efficiently, and safely. |
Case presentation |
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A 72 year old man with a past medical history of coronary artery bypass grafting, mitral valvular repair surgery, and prior RF ablation for typical right atrial flutter, presented with daily occurrence of atrial tachycardia (Figure 1) causing symptoms of palpitations and dyspnoea. Given the highly symptomatic and drug-refractory (beta-blockers, calcium channel blockers, and sotalol) nature of the arrhythmia, after counselling and informed consent, the patient underwent invasive electrophysiology (EP) evaluation and RF ablation.
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The procedure was performed in a postabsorptive state with minimal use of intravenous midazolam and fentanyl to achieve conscious sedative state that would allow patient's full co-operation for the duration of the procedure and safe mapping condition. Intracardiac electrograms from the high right atrium, His-bundle location, coronary sinus, and the right ventricular midseptal region were simultaneously recorded and displayed with surface ECG on a multichannel recorder (Cardiolab, Prucka Engineering, USA). The patient was in clinical tachycardia which, based on P-wave morphology (upright in the inferior leads), intracardiac activation pattern, and response to standard EP manoeuvres, was defined as left atrial tachycardia at cycle length of 340 ms. Intracardiac echocardiogram was performed to rule out left atrial clot and assist with transeptal puncture using Accu-NavTM phased array catheter (Biosense-Webster, USA). Intravenous heparin, 10 000 units bolus followed by infusion at 1200 units/h was administered and the dosage adjusted to keep the activated clotting time (ACT) between 275 and 300 s following transeptal catheterization. Mapping and ablation in the left atrium was subsequently performed using a 4-mm tip Navistar-RMTTM catheter (Biosense-Webster, USA). Electroanatomical mapping was performed using CARTO-RMT integration (Stereotaxis Inc.) system. Previously acquired computer tomographic (CT) images of the left atrium were also integrated with electroanatomical map using CARTO-Merge software (Figure 2).
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Electroanatomic activation mapping confirmed a focal left atrial tachycardia originating from the anteroseptal location (Figure 2). Intracardiac electrograms recorded at the earliest site were 30 ms before the inscription of surface P-waves. Using magnetic navigation, RF ablation was performed at this site. Stockert RF® generator (Biosense-Webster, USA) was used to deliver RF in a temperature-controlled mode (maximum temperature 50°C, power 30 W, duration 60 s). A single RF lesion (mean temperature 43°C, mean power 27 W, mean impedance 91 ohms) application resulted in prompt termination of the tachycardia with profound possibly vagally-induced bradycardia (6.5 s pause) necessitating cessation of RF delivery (Figure 3). Subsequently, four contiguous additional insurance RF lesions were applied circumferentially surrounding the success site (total ablation lesions 5, total ablation time 236 s, average temperature 41°C, average power 28 W, average impedance 88 ohms). Post ablation, the atrial tachycardia could no longer be induced in spite of aggressive stimulation protocol (decremental burst pacing up to 300 ms and up to three extrastimuli at progressively short coupling intervals to refractoriness in the right and left atria and the coronary sinus) as well as the use of intravenous isoproterenol (up to 2 µg/min).
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The total procedure time was 275 min (inclusive of screening for magnet safety, patient preparation, vascular access, catheter placement, EP evaluation, transeptal puncture, LA mapping and ablation, and vascular haemostasis after removal of all catheters). The LA mapping time was 28 min; and the total fluoroscopy time was 29 min. The patient received a total of 5 mg of midazolam and 275 µg of fentanyl over the total duration of the procedure so that stable patient position is achieved for safe mapping using MNS.
The patient has remained symptoms-free during the 6 months follow-up period after the ablation.
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Discussion |
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Briefly, the Stereotaxis NiobeTM remote MNS is composed of two computer-based remotely controlled permanent earth magnets positioned relative to each other on either side of the fluoroscopy table, a computer-controlled mechanical device (Cardiodrive, Stereotaxis Inc.) to advance and retract the catheter, and a video workstation-based User Interface (Navigant, Stereotaxis Inc.) displaying navigation vectors.1
–7 In conjunction with this technology, the use of CARTO-Merge software allows to integrate previously acquired CT images when three-dimensional electroanatomical mapping is performed with CARTO-RMT integration system (Stereotaxis Inc.).
Although, the conventional catheter technology based ablation procedure provides a high level of curative success in the treatment of various cardiac arrhythmias, difficult catheter manipulation resulting in inadequate mapping, inability to reach target sites for ablation, cardiac and vascular trauma, prolonged procedure time and radiation exposure may constitute some of the limitations to the success of the procedure. In that respect the Stereotaxis NiobeTM MNS demonstrated advantage of overcoming these limitations, and thus is quite promising for its applicability during RF ablation of various arrhythmias.1–7 These include slow pathway ablation and modification for atrioventricular nodal re-entry (including ablation in a patient with persistent left superior vena cava), accessory bypass tracts (including septal tracts) and even circumferential pulmonary vein ablation for atrial fibrillation.1–7 In terms of more complex procedures such as circumferential pulmonary vein isolation using Stereotaxis NiobeTM MNS, it is noteworthy that Di Biase et al.7 recently reported ineffective complete pulmonary vein isolation and the propensity for charring on the ablation catheter tip. It is worth to point out that the investigators after noting charring with RF delivered at higher power of 50 W for longer duration of 60 s changed the RF delivery settings to lower power of 40 W for shorter duration of 45 s. The limitations of charring and inadequate ablation were not encountered by Pappone et al.5 who reported that after a period of adequate learning curve the total procedure and ablation time shortened considerably. Furthermore, many more mapping points regardless of their location could be collected by the Stereotaxis NiobeTM remote MNS for electroanatomical CARTOTM mapping.5 This, in our opinion, is perhaps the most useful advantage of the technology in addition to the advantage of achieving optimal catheter position for delivery of RF energy and to return to the target sites and the areas of interest with precision.
From our experience in general, and this case in particular (where the entire mapping and ablation procedure was performed safely, effectively, and efficiently with remote navigation), we feel that Stereotaxis NiobeTM MNS potentially has wide applicability in the area of interventional ablation therapy of complex cardiac arrhythmias. However, we also believe that it is with the future reports from the ‘new’ operators like us when carefully taken into consideration with the experience of the ‘established’ operators that the true place of the Stereotaxis NiobeTM MNS in patient care would be better defined.
Conflict of interest: none declared.
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References |
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[1] Faddis MN, Blume W, Finney J, Hall A, Rauch J, Sell J, et al. Novel, magnetically guided catheter for endocardial mapping and radiofrequency catheter ablation. Circulation (2002) 106:2980–5.
[2] Faddis MN, Chen J, Osborn J, Talcott M, Cain ME, Lindsay BD. Magnetic guidance system for cardiac electrophysiology: a prospective trial of safety and efficacy in humans. J Am Coll Cardiol (2003) 42:1952–8.
[3] Ernst S, Ouyang F, Linder C, Hertting K, Stahl F, Chun J, et al. Initial experience with remote catheter ablation using a novel MNS: magnetic remote catheter ablation. Circulation (2004) 109:1472–5.
[4] Ernst S, Ouyang F, Linder C, Hertting K, Stahl F, Chun J, et al. Modulation of the slow pathway in the presence of a persistent left superior caval vein using the novel MNS. Niobe Europace (2004) 6:10–4.[CrossRef]
[5] Pappone C, Vicedomini G, Manguso F, Gugliotta F, Mazzone P, Gulletta S, et al. Remote catheter navigation for atrial fibrillation ablation. J Am Coll Cardiol (2006) 47:1390–400.
[6] Chun JKR, Ernst S, Matthews S, Schmidt B, Bansch D, Boczor S, et al. Remote-controlled catheter ablation of accessory pathways: results from the magnetic laboratory. European Heart Journal (2007) 28:190–5.
[7] Di Biase L, Fahmy TS, Patel D, Bai R, Civello K, Wazni OM, et al. Remote magnetic navigation: human experience in pulmonary vein ablation. J Am Coll Cardiol (2007) 50:868–74.
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