Europace Advance Access published online on June 3, 2008
Europace, doi:10.1093/europace/eun139
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Implantation of single-lead atrioventricular permanent pacemakers guided by electroanatomic navigation without the use of fluoroscopy
Arrhythmia and Cardiac Pacing Unit, Cardiology Department, Hospital Clinico Universitario, Av Blasco Ibanez, 17, 46010 Valencia, Spain
Manuscript submitted 11 March 2008. Accepted after revision 6 May 2008.
* Corresponding author. Tel/fax: +34 963 862 658.E-mail address: ruiz_ric{at}gva.es
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Abstract |
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Aims: Fluoroscopy is the standard and almost unique tool used for cardiac imaging during permanent pacemaker implantation, and its use implies exposure of patients and operators to radiation. The usefulness for this purpose of electroanatomic systems not based on fluoroscopy is unknown. Our aim was to study the feasibility of implanting single-lead VDD pacemakers without the use of fluoroscopy.
Methods and results: EnSite NavX®, a catheter navigation tool based on the creation of a voltage gradient across the thorax of the patient, was used as an exclusive imaging tool during the implantation of single-lead atrioventricular (VDD) permanent pacemakers in 15 consecutive patients with atrioventricular block and normal sinus node function. A retrospective series of 15 consecutive patients in whom VDD pacemakers were implanted under fluoroscopic guidance was used as a control group. The pacemaker could be implanted in all patients. Time spent to obtain the right ventricle anatomy was 10.1 ± 5.4 min and time to place the lead in an adequate position was 10.1 ± 7.8 min. Total implant time was 59.3 ± 15.6 min (51.5 ± 12.3 min in the control group; P = 0.14). In one patient, a short pulse of radioscopy was needed for a correct catheterization of the subclavian vein. No complications were observed during the procedure. One lead dislodgement that required re-operation was detected 24 h after implantation. At 3 months follow-up, all pacemakers were functioning properly, with adequate pacing and sensing thresholds.
Conclusion: Electroanatomic navigation systems such as NavX can be used for cardiac imaging during single-lead atrioventricular pacemaker implantation as a reliable and safe alternative to fluoroscopy.
Key Words: Pacemaker, Non-fluoroscopy imaging, Heart block, Mapping, Electroanatomic navigation
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Background |
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Transvenous implantation of pacemakers is performed with the aid of fluoroscopy, as the standard tool for visualization of cardiac chambers and thoracic structures. It implies radiation for patients and operators and, to the best of our knowledge, there are no alternative tools. Recently, some devices intended for navigation of catheters through the cardiac chambers and vascular structures have been developed.1
–6 They are used to facilitate mapping and ablation procedures of arrhythmias, even though their use has been described as an allied tool for pacemaker implantation in anecdotic cases.7,8 Our objective was to investigate the feasibility of implantation of permanent single-lead atrioventricular (VDD) pacemakers guided only by an electroanatomic navigation system and without the use of radioscopy. |
Methods |
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In 15 consecutive patients, submitted for implantation of a permanent single-lead VDD pacemaker because of atrioventricular block with normal sinus node function, the implantation was performed with the aid of an EnSite NavX® system (Endocardial Solutions, Inc., St Paul, MN, USA). NavX is an intracardiac non-fluoroscopic electroanatomic navigation tool based on the creation of an electric voltage gradient. Three pairs of adhesive electrodes are placed on the chest configuring orthogonal axes, and a low-power 5.7 kHz electrical potential is generated across each pair of electrodes. The voltage gradient from each axis generates a three-dimensional navigation field. The system is able to accurately locate the position of any electrode placed within the navigation field by measuring the local voltage detected from it. Up to 64 electrodes (maximum of 8 catheters with up to 20 electrodes per catheter) can be located simultaneously at a sampling rate of 93 Hz. The system also permits the accurate construction of a geometric contour of the patient's cardiac chamber subject to study by sweeping a conventional catheter in its interior, defining the endocardial boundaries.
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The procedures were performed in the post-absortive, fasting state. All patients gave informed written consent. Under local anaesthesia, the left subclavian vein was canulated with a 6F valvulated sheath and a subcutaneous pouch was dissected. A quadripolar electrophysiology catheter (interelectrode distance 0.5 cm) was introduced and used to build the contour of the right ventricle and to mark references of subclavian, innominate, and superior vena cava veins. The catheter was then withdrawn and the 6F sheath replaced by a 9F or 10F peelable introducer for the pacemaker lead. Passive fixation leads were used in all cases. The four electrodes of the pacemaker lead (two atrial and two ventricular) were connected to the NavX system. The pacemaker lead tip was positioned in the apex of the right ventricle using electroanatomic navigation, the position was then confirmed by 12-lead electrocardiogram (paced QRS complex morphology), and sensing and pacing thresholds were measured (Figures 1 and 2). Ventricular threshold
1 V at 0.5 ms of pulse duration, ventricular sensing 
5 mV, and atrial sensing 0.7 mV were considered acceptable. The lead was sutured to the muscular layer and connected to a VDD pacemaker that was inserted in the pouch. After confirming the normal function of the system, a single shot of fluoroscopy confirmed the position of the lead. The subcutaneous tissue was sewn with a resorbable suture and the skin with staples. Total and partial times of the procedure were measured. All procedures were performed by the same two experienced cardiologists. Patients were discharged the day following the operation, after checking the function of the pacemaker and obtaining an X-ray chest film. Follow-up was performed 3 months after the procedure in the outpatient pacemaker clinic.
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The results were compared with that obtained in 15 consecutive patients who were implanted with fluoroscopy and were retrospectively analysed.
Data are expressed as mean ± SD and as percentage.
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Results |
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The mean age of the patients was 72 ± 13 years (range: 51–89) and six were male. Clinical characteristics of the patients are shown in Table 1. Manufacturers of the pacemakers were as follows: Boston Scientific/Guidant (Boston Scientific Corporation, Natick, MA, USA) (n = 5), Medtronic Inc. (Minneapolis, MN, USA) (n = 3), Vitatron (Arnhem, The Netherlands) (n = 1), and Sorin/Ela Medical (Sorin SPA, Milano, Italy) (n = 6). The diameters of the leads were 9F (n = 11) and 10F (n = 4) with interpolar distances of 13 (n = 10) and 13.5 cm (n = 5). The duration of the procedures and pacing/sensing parameters obtained during the implantation are shown in Table 2. Note that acquisition of anatomy took only a mean of 10 min, for a mean total procedure duration of 59 min. Only in one patient, the use of X-ray guidance was necessary due to the recurrent deviation of the guidewire from the subclavian to the internal jugular vein. Once clear subclavian access was gained, the procedure could be continued without fluoroscopy. No complications were recorded during the procedure in any patient. Before discharge, one patient had to be re-operated because of dislodgment of the lead, which was repositioned uneventfully using a conventional approach. Age and gender of the patients in the control group were similar to the patients in the study group. In the control group, the total procedure time (51 ± 12 min) was slightly shorter than in the study group, but the difference was not significant (P = 0.14). Pacing and sensing parameters obtained at the implantation were similar in both groups. No complications were observed in the control group.
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Patients were visited in the outpatient clinic for follow-up 3 months after implantation. No complications were seen at follow-up. Ventricular threshold and sensing amplitudes were in normal ranges and are shown in Table 2.
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Discussion |
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To the best of our knowledge, this paper is the first to describe a series of permanent pacemaker implantation without the use of fluoroscopy and with the aid of an electroanatomic navigation system not based on the use of X-ray.
X-ray is the standard and unique tool used nowadays to guide pacemaker leads to their position in the cardiac chambers. It implies radiation exposure, with doses that are usually negligible for patients, but not for operators who are exposed in every implant9 and in whom the accumulative effects can have deleterious consequences. In specific groups of patients, such as children, fertile women, and, specially, pregnant women, exposition to X-ray has to be avoided, being contraindicated in the latest group. Therefore, the development of an alternative technique would be of great interest to make the procedure safer for patients and operators when necessary.
Recently, some systems have been developed to help in the placement and navigation of catheters during electrophysiological studies and ablation procedures. The Biosense CARTO® system uses a magnetic field to localize a dedicated catheter.1 Although it has been used to help in a permanent pacemaker implantation in a patient with an Ebstein's anomaly,7 it is not useful as a solitary tool, because it only localizes and represents dedicated special catheters. The LocaLisa® system4 is based on principles similar to that of NavX and can accurately localize regular intracardiac electrodes, but it is not implemented with the capability of reconstruction of the cardiac chamber anatomy. Finally, the RPM® system5 can locate regular catheters, but a special echo-reference catheter has to be used, usually placed in the coronary sinus, with the disadvantage of its cost.
The NavX system not only reproduces the three-dimensional position of a standard catheter but can also represent an anatomic contour of the cardiac chamber subject to study.2,3 Recently, a case of atrioventricular conduction ablation with the implantation of a single-chamber ventricular pacemaker has been described with the exclusive aid of this system.8 With NavX, the anatomy is acquired through the movement of a catheter inside the cavity. For that purpose, a regular quadripolar catheter was used in this study, but as any catheter can be used, it is feasible that the anatomy could be acquired directly with the pacemaker lead, thus saving the cost of the diagnostic catheter. The recording of the intracardiac electrograms and pacing manoeuvres during manipulation of the catheter and/or pacemaker lead are valuable tools in the correct identification of the intracardiac structures and the definitive placement of the lead. We did not find it difficult to cross the tricuspid annulus nor to place the lead in the right ventricular apex, as reflected by the time needed for that purpose. As previously speculated,8 the use of atrioventricular single leads (for VDD mode of pacing) makes the procedure easier because the atrial pair of electrodes allows the representation of a longer part of the lead by the system, including the distal (ventricular) and proximal (atrial) pair of electrodes, so the course of the lead is visible almost from the superior vena cava to the right ventricular apex. It can be argued that the manipulation of catheters and leads inside the cardiac chambers without the aid of fluoroscopy may be dangerous because perforation or damage to cardiac structures could be difficult to prevent. But navigational tools, and NavX among them, have proved to be safe when performing electrophysiological studies without the use of fluoroscopy.6 Moreover, the recent widespread use of CARTO and NavX for radiofrequency ablation procedures, especially atrial fibrillation and ventricular tachycardia, has demonstrated their safety.
In our series, the only complication observed during implantation was related to the subclavian vein catheterization and not to the implantation itself. An early lead dislocation was the only post-op complication in this series, but dislodgement of pacemaker leads is also observed when using fluoroscopy. The technique, performed by two cardiologists experienced in pacemaker implants, did not penalize very much the duration of the procedure, and the implant could be done in all the cases.
It would be necessary to perform a controlled study with a larger series of patients to assess the real figures of this approach and to accurately compare the standard and the electroanatomic techniques, but the results obtained with our cases point to the feasibility and to comparable results. We think that, at the present time, electroanatomic navigation can be an alternative to fluoroscopy in selected cases rather than a technique of widespread use, but in these cases, especially with pregnant women, can be problem solving. However, it seems that trends in cardiac imaging point to the integration of Echo images, X-ray, CT scan, magnetic resonance imaging, and images from navigation tools, so it would be reasonable to think that in near future, device implantations will be made with the help of a system integrating some of these types of cardiac imaging.
In conclusion, electroanatomic navigation systems such as NavX can be used for cardiac imaging during single-lead atrioventricular pacemaker implantation as a reliable and safe alternative to fluoroscopy.
Conflict of interest: none declared.
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References |
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