|
| HOME | SUBSCRIPTIONS | CURRENT ISSUE | PAST ISSUES | CARDIOSOURCE | SEARCH | HELP | FEEDBACK |
|
|
|
|||||||||
|
|||||||||||
|
J Am Coll Cardiol, 2006; 47:1390-1400, doi:10.1016/j.jacc.2005.11.058
(Published online 13 March 2006). © 2006 by the American College of Cardiology Foundation |
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Department of Electrophysiology, San Raffaele Scientific Institute, Milan, Italy
Manuscript received August 23, 2005; revised manuscript received November 9, 2005, accepted November 16, 2005.
* Reprint requests and correspondence: Dr. Carlo Pappone, Department of Arrhythmology, University Hospital San Raffaele, Via Olgettina, 60, 20132 Milan, Italy (Email: carlo.pappone{at}hsr.it).
 |
Abstract |
|---|
 Top Abstract MethodsResultsDiscussionReferences |
|---|
BACKGROUND: No data are available on feasibility of remote navigation for AF ablation.
METHODS: Forty patients underwent CPVA for symptomatic AF using the NIOBE II remote magnetic system (Stereotaxis Inc., St. Louis, Missouri). Ablation was performed with a 4-mm tip, magnetic catheter (65°C, maximum 50 W, 15 s). The catheter tip was guided by a uniform magnetic field (0.08-T), and a motor drive (Cardiodrive unit, Stereotaxis Inc.). Left atrium maps were created using an integrated CARTO RMT system (Stereotaxis Inc.). End point of ablation was voltage abatement >90% of bipolar electrogram amplitude.
RESULTS: Remote ablation was successful in 38 of 40 patients without complications. The median mapping and ablation time was 152.5 min (range, 90 to 380 min) but was much longer in the first 12 patients (192.5 min vs. 148 min; p = 0.012). Median ablation time was 49.5 min (range, 17 to 154 min), but it was much shorter in the last 28 patients than in the first 12 patients (49 min vs. 70 min; p = 0.021). Patients receiving remote ablation had longer procedure times than control patients (p < 0.001) with similar mapping time but shorter ablation time on right-sided pulmonary veins. Many more mapping points regardless of their location were collected remotely (p < 0.001).
CONCLUSIONS: Remote magnetic navigation for AF ablation is safe and feasible with a short learning curve. Although all procedures were performed by a highly experienced operator, remote AF ablation can be performed even by less experienced operators.
| ||||||||||
|
Methods |
|---|
|
TopAbstractMethodsResultsDiscussionReferences |
|---|
|
Magnetic catheter. A 4-mm flexible catheter (NaviStar-RMT, Biosense Webster, Diamond Bar, California) incorporating a small permanent magnet in the tip and additional magnets in the distal portion of the device can be deflected in the desired direction and steered by the magnetic navigation system (Fig. 1). The catheter is advanced and retracted by a mechanical device (Cardiodrive, Stereotaxis Inc.). All magnetic field vectors can be stored and, if necessary, reapplied while the magnetic catheter is navigated automatically (Fig. 2). The video workstation-based User Interface (Navigant, Stereotaxis Inc.) used together with the permanent magnets and the Cardiodrive unit (Stereotaxis Inc.) permits accurate orientation changes of the catheter by 1° increments and advancement or retraction by 1-mm steps (Fig. 3). Additionally, X-ray image data can be transferred from the X-ray system to the user interface of the magnetic navigation system to provide an anatomical reference.
|
|
|
|
Remote mapping and ablation protocol. First, the transseptal sheath was positioned just proximal to the fossa ovalis after a magnetic catheter was placed into the left atrium (Fig. 2). After synchronizing with respiratory and cardiac cycles, such as inspiration and end diastolic period, a pair of best matched RAO/LAO images were transferred and kept into Navigant screen as background references for orientation and navigation (Fig. 3). Because two distinct planes of X-ray data are available, spatial locations in two dimensions can be localized by marking on corresponding points in the X-ray images and using epipolar geometry. The user marks the support or base of the catheter (the distal portion of the sheath) on the pair of X-ray images. This provides Navigant with the data needed to compute field orientations corresponding to particular targets. Next, a PV location was selected, either as a target by marking on suitable locations in the reference X-ray images, or by selecting a preset magnetic field vector based on selected study protocol from the list on Navigant (Figs. 3 and 4). Throughout, points were simultaneously acquired for mapping (Fig. 5). The NaviStar-RMT (Biosense Webster) magnetic catheter was used for both mapping and ablation.
|
Statistical analysis. Continuous variables are expressed as median and interquartile range, with range values, and compared by use of the Mann-Whitney U test. For categorical variables the chi-square test was performed, unless the exact test was required for frequency tables when more than 20% of the expected values were <5. Statistical tests were performed with SPSS for Windows (version 13.0.1, SPSS Inc., Chicago, Illinois).
|
Results |
|---|
|
TopAbstractMethodsResultsDiscussionReferences |
|---|
The transseptal sheath was positioned just proximal to the fossa ovalis to allow the greatest movement of the magnetic wire catheter. Before mapping, the position of the magnetic catheter was also controlled by manual advancement or retraction of the catheter through the vascular sheath. Sheath insertion and positioning of diagnostic catheters, including the magnetic catheter, required a median of 7.9 min (range, 5 to 12 min). Median fluoroscopy exposure was 32.3 min (range, 21.8 to 81.4 min). After crossing the atrial septum and positioning the transseptal sheath, the physician left the interventional room to perform mapping and ablation from the control room. Remote magnetic navigation and ablation to all targeted sites was successfully achieved in 38 of 40 patients without complications.
Navigation to the PV ostia was guided by real-time biplanar fluoroscopic images, but venography was not performed to identify the location of PV ostia. We accurately navigated all PVs (Fig. 3), and then, by advancing magnetic catheter using the Cardiodrive unit (Stereotaxis Inc.), we acquired a median of 274 points (range, 139 to 382 points) for accurate maps of the left atrium (Table 1, Fig. 5). Minimal orientation changes of the catheter up to 5° were used for acquiring points around venoatrial junction region and up to 15° for the remaining left atrial reconstruction. At the beginning of the learning curve and for the first 10 patients, the catheter orientation was frequently adjusted using the keyboard rotation and deflection keys to reach mapping targets. In all cases, the catheter was retracted and advanced to access all PVs by using this sequence when feasible: left superior pulmonary vein (LSPV), LIPV, right superior PV, and finally right inferior PV. Afterwards, the mitral valve annulus and the left atrial appendage were accessed by selecting different field directions on NaviSphere. Finally, the magnetic catheter was navigated in sequence to the posterior wall, the roof, the septal wall, and the anterior wall.
Remote catheter ablation. In the first three patients, both mapping and ablation were extremely time consuming and in two of them RF applications were made manually with standard catheters. In the remaining 38 patients, the magnetic catheter successfully reached all targets. We started the encircling lesions around the left-sided PVs, which were completed by repeatedly moving and adjusting the magnetic catheter. The right-sided PVs were then encircled. During this process, the NaviSphere display orientation was adjusted to match that of the CARTO map to facilitate adjustment of the catheter directly from the NaviSphere. No interference of magnetic field with the surface 12-lead electrocardiogram (ECG) was observed in any patient. At the end of the procedure and at discharge, all patients were in stable sinus rhythm without antiarrhythmic drugs.
Learning curve. Overall, the median procedure time including mapping and ablation was 152.5 min (range, 90 to 380 min). In the last 28 patients, this time shortened to 148 min (range, 90 to 209 min) (Table 1). The median ablation time was 49.5 min (range, 17 to 154 min) for encircling all PVs. The mitral isthmus line and posterior lines were performed in a median of 12.5 min each. To evaluate the impact of the magnetic navigation learning curve for mapping and ablation, we compared procedural times for the first 12 patients and the last 28 patients. The median procedure time, including both mapping and ablation times, was 192.5 min (range, 92 to 380 min) in the first 12 patients and 148 min (range, 90 to 209 min) in the last 28 patients (p = 0.012) while ablation time significantly shortened in the last 28 patients (Table 1, Fig. 6). In the first 12 patients, a median of 34.5 min (range, 22.4 to 81.4 min) of fluoroscopy was used for mapping and ablation while it shortened to 30.3 min (range, 21.8 to 60.4 min) in the last 28 patients (p = 0.065) (Table 1).
|
Many more CARTO mapping points were collected in the remote group than in control group (Table 1). Vagal denervation, defined as elicitation and abolition of vagal reflexes during the procedure, did not differ in both groups (39.3% in remote ablation vs. 28.6% in standard approach; p = 0.397). Remote ablation time of right-sided PVs was shorter than standard ablation but similar for the remaining targets (Table 2). Atrial fibrillation was converted to sinus rhythm in two and three patients during standard CPVA and remote CPVA, respectively. At the end of the procedure, electrical cardioversion was successful in all patients in AF, regardless of the procedure.
|
|
Discussion |
|---|
|
TopAbstractMethodsResultsDiscussionReferences |
|---|
Remote magnetic navigation and ablation. Precise target localization and catheter stability are prerequisite for adequate RF applications minimizing risks of potential complications. Stiff manually deflectable catheters with unidirectional or bidirectional deflection radius have several inherent limitations as stable wall contact may be difficult to achieve particularly in regions of complex cardiac anatomy. Usually, challenging sites within the LA include the anterior aspect of right-sided PVs, the narrow ridge that separates the left atrial appendage from the left PVs, and/or the mitral isthmus where movement of the valve greatly limits catheter stability. Incomplete lesions in such areas, particularly at mitral isthmus, facilitate development of multiple gaps, which may in the majority of the cases lead to post-ablation incessant macro-re-entrant atrial tachycardia (2). Despite aggressive protocols, a high rate of conduction recurrence across electrically disconnected segments late after ablation with standard, manually deflectable catheters has been reported to occur in up to 80% of the PVs four to five months after ablation (5). In the current study, all targeted sites regardless of their anatomic position were successfully ablated remotely, and abatement of all atrial potentials was reached rapidly in all targeted sites, usually disappearing within 10 s. This enhanced flexibility and compliance of the catheter could also compensate for cardiac and respiratory motion. These findings confirm previous studies in animals that demonstrated lesion block after RF applications by magnetic catheter even on trabeculated myocardium, which is the most difficult area to achieve linear conduction block (6). Vagal denervation was also obtained similarly to standard CPVA (8).
Catheter stability and sheath positioning. In the current study, to achieve optimal catheter stability associated with the greatest freedom of movement for navigation even in critical areas, initial positioning of the sheath was made just proximal to the fossa ovalis for mapping and ablation of left-sided PVs or lower in the inferior vena cava orifice for the right-sided PVs. Sometimes, the sheath may pull back during navigation, together with the soft magnetic catheter. When this inadvertently occurs, it is possible to rapidly regain access to the transseptal puncture simply by applying a stored magnetic field corresponding to entry into the left atrium. In this study, navigation to the right-sided PV region required much larger catheter deflections with shorter ablation times as compared with standard CPVA. These were more easily obtained positioning the sheath into the inferior vena cava orifice. Conversely, positioning of the sheath proximal to the fossa ovalis was required for better remote navigation and ablation of left-sided PVs. The same positioning was used for successful ablation of the ridge between the left atrial appendage and the LSPV. Reapplication of a previously applied magnetic field vector was useful to repeatedly navigate to previously visited targets decreasing ablation time in challenging sites.
CARTO RMT mapping integration system. In the current study, more mapping points were obtained with the NIOBE system (Stereotaxis Inc.) than with manual catheter manipulation because it is easier to obtain multiple points with this system assuring in all cases a homogeneous mapping density for successful ablation even of particularly challenging regions. The CARTO RMT (Stereotaxis Inc.) system was also able to send real-time catheter tip location and orientation data to the magnetic navigation system, which include target locations, groups of points, and anatomical surface information from the electroanatomical map to the magnetic navigation system. Also, magnetic field orientations corresponding to specific map points were stored on the magnetic navigation system and were re-applied if desired to repeatedly and accurately return to previously visited locations on the map.
Comparison of remote ablation with standard, manually deflectable catheters. Circumferential PV ablation, which is one of the two current predominant approaches for AF ablation, is a complex procedure requiring a rather extensive learning curve. This relatively long learning curve could limit the wide application of the procedure in the clinical practice (9). The current study is the first report in the literature prospectively documenting a single center experience of using remote magnetic navigation for AF ablation. Although an expert operator with extensive experience with standard, manually deflectable catheters performed all procedures, early results suggest that remote navigation is indeed a simple, safe, and useful system for AF ablation not requiring a substantial learning curve as the end point was successfully reached in almost all patients (38 of 40). In the first few patients, the procedure duration and fluoroscopy exposure times were excessively long as they were an expression of the underlying learning curve. This was mainly due to the need to confirm catheter positioning and stability visually during both mapping and RF applications. Both mapping and ablation were performed from control room due to remote navigation nature, reducing in all cases fluoroscopic exposure time for the operator. Although the manual approach may well be operator-dependent, the remote approach is not solely dependent on a single operator, but is most dependent on a well-trained team. This could explain why the overall procedure time was longer in the remote group than in the control group, while mapping time or PV denervation in both approaches remained similar. However, we believe that procedure times will improve as more experience is gained with it in the future. Ablation time of circumferential lesions around right-sided PVs was shorter, remotely suggesting that with this approach there are no specific challenging sites avoiding unnecessary RF energy applications.
Previous studies. There are no data on remote magnetic catheter navigation for AF ablation in humans. Our feasibility data confirm a recent study with this method in 42 patients with atrioventricular nodal re-entrant tachycardia where no complications were reported (7). This system was successful in performing completely controlled mapping and slow pathway modulation in 27 patients or ablation in 15 patients with a mean overall procedure time of 145 min calculated from puncture to sheath extraction.
Complications. No acute complications occurred during magnetic navigation and ablation confirming previous experimental and clinical studies on safety (6,7,10). In animals, attempts to intentionally perforate the heart with the magnetic catheter did not result in significant endocardial injury indicating a very low risk of cardiac injury (6). Our experience confirms these experimental observations as complex tip movements of the soft catheter within the left atrium did not result in any complications. However, further larger studies are required to evaluate whether remote navigation is associated with less complications than standard CPVA (9,11). In our initial experience, echocardiography performed before and after the procedure did not show abnormalities. Although previous animal studies reported interfering signal components in the presence of the magnetic field on surface ECG (1), we did not observe any interference with both surface ECG and intracardiac electrograms.
Study limitations. Mapping and navigation are displayed on separated screens, which may cause longer procedure times. Therefore, it seems to be reasonable to provide a single screen to improve remote procedure times.
The present and the future. At present, our experience is limited to a relatively small number of patients, and there are incomplete data on long-term follow-up. The learning curve with this navigation system appears to be short, but our experience is limited just to 40 cases performed by a highly skilled operator. Previous experience with magnetic navigation in the left atrium among 13 patients with left-sided accessory pathways also indicated that PV ostia stability may be problematic just at the beginning of the learning curve (10). The results of this study have important clinical implications as magnetic soft catheters can easily be navigated precisely and safely in the left atrium even in challenging sites.
|
Acknowledgments |
|---|
|
Footnotes |
|---|
|
References |
|---|
|
TopAbstractMethodsResultsDiscussionReferences |
|---|
This article has been cited by other articles:
|
|
 |
|
  B. Schmidt, K. R. J. Chun, R. R. Tilz, B. Koektuerk, F. Ouyang, and K.-H. Kuck Remote navigation systems in electrophysiology Europace, November 1, 2008; 10(suppl_3): iii57 - iii61. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 W. Saliba, V. Y. Reddy, O. Wazni, J. E. Cummings, J. D. Burkhardt, M. Haissaguerre, J. Kautzner, P. Peichl, P. Neuzil, V. Schibgilla, et al. Atrial fibrillation ablation using a robotic catheter remote control system initial human experience and long-term follow-up results. J. Am. Coll. Cardiol., June 24, 2008; 51(25): 2407 - 2411. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 Y. Minami, H. Chung, M. Kudo, S. Kitai, S. Takahashi, T. Inoue, K. Ueshima, and H. Shiozaki Radiofrequency Ablation of Hepatocellular Carcinoma: Value of Virtual CT Sonography with Magnetic Navigation Am. J. Roentgenol., June 1, 2008; 190(6): W335 - W341. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. Pappone and V. Santinelli Safety and efficacy of remote magnetic ablation for atrial fibrillation. J. Am. Coll. Cardiol., April 22, 2008; 51(16): 1614 - 1615. [Full Text] [PDF]
|
|
|
|
|
|
L. Di Biase, J. D. Burkhardt, R. A. Schweikert, W. I. Saliba, and A. Natale Reply J. Am. Coll. Cardiol., April 22, 2008; 51(16): 1615 - 1616. [Full Text] [PDF]
|
|
|
|
|
|
R. Mehta, D. T. Hart, B. S. Nagra, Z. Liu, and B. K. Kantharia Successful ablation of focal left atrial tachycardia using Stereotaxis NiobeTM remote magnetic navigation system Europace, March 1, 2008; 10(3): 280 - 283. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 C. Pappone and V. Santinelli Non-fluoroscopic mapping as a guide for atrial ablation: current status and expectations for the future Eur. Heart J. Suppl., December 1, 2007; 9(suppl_I): I36 - I47. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
B. D. Lindsay Is Pulmonary Vein Antrum Isolation a Critical Determinant of Recurrent Arrhythmias After Ablation of Atrial Fibrillation? J. Am. Coll. Cardiol., August 28, 2007; 50(9): 875 - 876. [Full Text] [PDF]
|
|
|
|
|
|
L. Di Biase, T. S. Fahmy, D. Patel, R. Bai, K. Civello, O. M. Wazni, M. Kanj, C. S. Elayi, C. K. Ching, M. Khan, et al. Remote Magnetic Navigation: Human Experience in Pulmonary Vein Ablation J. Am. Coll. Cardiol., August 28, 2007; 50(9): 868 - 874. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
H. Calkins, J. Brugada, D. L. Packer, R. Cappato, S.-A. Chen, H. J.G. Crijns, R. J. Damiano Jr, D. W. Davies, D. E. Haines, M. Haissaguerre, et al. HRS/EHRA/ECAS Expert Consensus Statement on Catheter and Surgical Ablation of Atrial Fibrillation: Recommendations for Personnel, Policy, Procedures and Follow-Up: A report of the Heart Rhythm Society (HRS) Task Force on Catheter and Surgical Ablation of Atrial Fibrillation Developed in partnership with the European Heart Rhythm Association (EHRA) and the European Cardiac Arrhythmia Society (ECAS); in collaboration with the American College of Cardiology (ACC), American Heart Association (AHA), and the Society of Thoracic Surgeons (STS). Endorsed and Approved by the governing bodies of the American College of Cardiology, the American Heart Association, the European Cardiac Arrhythmia Society, the European Heart Rhythm Association, the Society of Thoracic Surgeons, and the Heart Rhythm Society. Europace, June 1, 2007; 9(6): 335 - 379. [Full Text] [PDF]
|
|
|
|
 |
|
 V. Y. Reddy, P. Neuzil, Z. J. Malchano, R. Vijaykumar, R. Cury, S. Abbara, J. Weichet, C. D. McPherson, and J. N. Ruskin View-Synchronized Robotic Image-Guided Therapy for Atrial Fibrillation Ablation: Experimental Validation and Clinical Feasibility Circulation, May 29, 2007; 115(21): 2705 - 2714. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. Aryana, A. d'Avila, E. K. Heist, T. Mela, J. P. Singh, J. N. Ruskin, and V. Y. Reddy Remote Magnetic Navigation to Guide Endocardial and Epicardial Catheter Mapping of Scar-Related Ventricular Tachycardia Circulation, March 13, 2007; 115(10): 1191 - 1200. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | SUBSCRIPTIONS | CURRENT ISSUE | PAST ISSUES | CARDIOSOURCE | SEARCH | HELP | FEEDBACK |
