Original article
135
Safety of the colonoscope magnetic imaging device (ScopeGuide) in patients with implantable cardiac devices
Authors
Gareth D. Corbett1, Yean C. Lim1, James C. Lee1, Alexey Chernolesskiy1, Peter J. Pugh2, Ewen A. B. Cameron1
Institutions
1
submitted 9. June 2013 accepted after revision 4. November 2013
Bibliography DOI http://dx.doi.org/ 10.1055/s-0033-1359044 Endoscopy 2014; 46: 135–138 © Georg Thieme Verlag KG Stuttgart · New York ISSN 0013-726X Corresponding author Ewen A. B. Cameron, MD Box 293 Endoscopy Unit, Addenbrooke’s Hospital Cambridge, CB2 0QQ UK Fax: +44-1223-348729 ewen.cameron@addenbrookes. nhs.uk
Department of Gastroenterology, Cambridge University Hospitals NHS Foundation Trust, Cambridge, United Kingdom Department of Cardiology, Cambridge University Hospitals NHS Foundation Trust, Cambridge, United Kingdom
Background and study aims: Use of the colonoscope magnetic imaging device (ScopeGuide, Olympus Medical Systems, Tokyo, Japan) is currently contraindicated by the manufacturer for patients with implantable cardiac devices, a group of patients that is increasing annually along with the number of colonoscopies performed in the era of colorectal cancer screening. This is the first study to examine the safety of ScopeGuide in patients with permanent pacemakers, implantable cardioverter defibrillators, and cardiac resynchronization therapy. Patients and methods: Nonimplanted cardiac devices were exposed to the electromagnetic field of ScopeGuide ex vivo and assessed for evidence of interference or change in device settings. Following this, consecutive patients attending device check clinics were prospectively recruited and exposed to the ScopeGuide electromagnetic field.
After an initial device check, patients underwent continuous external cardiac monitoring and device interrogation while a colonoscope was placed on the abdomen over clothing and connected to ScopeGuide to simulate colonoscopy. Patients were monitored for 2 minutes to assess for any interference. ScopeGuide was then disconnected and devices were checked for any change in settings. Results: A total of 230 patients were invited to participate and 100 were recruited to the study. There was no evidence of interference on device leads or change in programming following exposure to the electromagnetic field generated by ScopeGuide. Conclusion: ScopeGuide does not appear to cause interference or change in settings and is therefore likely to be safe for use in patients with implantable cardiac devices.
Introduction
ognized by many endoscopists to be a useful adjunct to colonoscopy, even though it probably provides little benefit to expert colonoscopists [6]. ScopeGuide is currently contraindicated for use in patients with implantable electronic medical devices due to the electromagnetic field it generates [7]. Accordingly, this adjunct cannot be used in patients with permanent cardiac pacemakers (PPMs) or implantable cardioverter defibrillators (ICDs), nor in those with implantable infusion devices or neurostimulator devices that are used for Parkinson’s disease [8], gastric dysmotility [9], and bladder dysfunction [10]. Due to their increasing number, the patients for whom this is most likely to affect in daily practice are those with implantable cardiac devices. These devices include PPMs inserted for treatment of bradyarrhythmias, ICDs inserted for primary or secondary prophylaxis of life-threatening ventricular arrhythmias, and cardiac resynchronization therapy devices (CRT) for treatment of heart fail-
!
Colonoscopy is the gold standard investigation for suspected colorectal cancer and is used in many countries as a screening tool in at-risk age groups. This technique is technically challenging and can be uncomfortable for patients, particularly if loops form in the colonoscope. The colonoscope magnetic imaging device (ScopeGuide, Olympus Medical Systems, Tokyo, Japan) was developed in the 1990 s [1, 2] to aid colonoscopy training and to allow early detection of loops, and is being used with increasing frequency. This technology utilizes magnetic coils along the length of the colonoscope to provide a 3 D real-time graphic representation of the instrument, which facilitates the early recognition of loops and has been shown to reduce cecal intubation time and discomfort, and improve completion rates by trainee endoscopists [3]. It also allows the localization of colonic tumors with an accuracy equivalent to that of radiological imaging [4, 5]. ScopeGuide is therefore rec-
Corbett Gareth D et al. Safety of ScopeGuide with implantable cardiac devices … Endoscopy 2014; 46: 135–138
This document was downloaded for personal use only. Unauthorized distribution is strictly prohibited.
2
Original article
ure. In 2009, a worldwide survey showed that the number of implanted cardiac devices was increasing in almost all of the countries surveyed, with over 1 million devices inserted worldwide [11]. In such patients, the concern regarding ScopeGuide use is that the electromagnetic field produced might interfere with the medical device. This could manifest as device inhibition (e. g. PPMs failing to pace when they should), device dysfunction (e. g. inappropriate pacing with PPMs or inappropriate DC shock delivery with ICDs), or interference with device settings (e. g. returning them to the factory preset mode). This risk is theoretical as there have been no reports of cardiac device malfunction during endoscopic procedures. Moreover, the recommendation of the manufacturer (Olympus) is not based on evidence of actual interference (personal communication with Olympus). We therefore sought to assess the actual safety of using ScopeGuide in patients with implantable cardiac devices.
Methods
Fig. 1 Patient simulator device connected to ex vivo pacemaker, with colonoscope and ScopeGuide positioned to emulate a colonoscopy. A, pacemaker programmer; B, patient simulator; C, pacemaker with programmer wand; D, colonoscope; E, ScopeGuide.
!
Phase 1: ex vivo assessment of interference To assess whether the electromagnetic field created by ScopeGuide would interfere with cardiac device function, an ex vivo study was first performed as a proof of concept safety check. ScopeGuide was set up immediately adjacent to an examination trolley on which a connected colonoscope was placed. A PPM and an ICD (Boston Scientific, Massachusetts, USA) were in turn placed into the center of the coiled colonoscope. Each device was connected to a cardiac simulator device (used for cardiac device setup and maintenance) and wirelessly to a cardiac device programmer to provide monitoring and allow for setting adjustment " Fig. 1). For each device, monitoring of both electrocardiogra(● phy (ECG) and electrogram (EGM) from a simulated intracardiac rhythm was performed. The device settings were then incrementally increased to the most sensitive setting in order to maximize the potential for electromagnetic interference (PPM ventricular sensing threshold increased from 2.5 mV to 0.5mV in 0.25-mV increments; ICD ventricular sensing threshold reduced from 2.5 mV to 0.5 mV in 0.25-mV increments).
Phase 2: in vivo assessment of interference Based on the results of the Phase 1 experiments and further technical information relating to the radiofrequency emission of ScopeGuide obtained from the manufacturer, a noninvasive experiment was designed to determine whether ScopeGuide would cause cardiac device interference. Ethical approval was obtained from the East Cambridge Research and Ethics Committee (Reference 12 /EE0075) and the study was registered on ClinicalTrials. gov (NCT01825525). All patients were invited to participate by letter prior to routine appointments for a maintenance check on their implantable cardiac device, and all participating patients provided written informed consent. Included patients were aged between 18 and 80 years and had any type of implantable cardiac device (PPM, ICD or cardiac resynchronization therapy device) and were without any cognitive deficit. The results of a previous study that investigated the probability of PPM interference from magnetic fields at the frequencies generated by power lines [12] were used to determine the optimal sample size in the present study. In the previous study, the authors reported an incidence of interference of ~2 %. Importantly,
despite detecting this level of interference, the UK National Grid states that the Medicines and Health Regulatory Authority (London, UK) have received no reports of power lines interfering with PPMs in vivo, which makes it unlikely that any have occurred [13]. A total of 100 patients were sought for this experiment as this sample size would provide a 95 % probability of detecting interference if it were to occur at an incidence of 3 %. This was also an achievable number of patients given the size of our unit. To ensure each implanted device was functioning properly prior to exposure to ScopeGuide, each patient underwent a standard device interrogation to check for any abnormal rhythms or other problems that may have occurred since the previous interrogation. The thresholds from each pacing lead were also tested (the lowest output at which capture is achieved). After this device check, a colonoscope (Olympus H260-DL with preinstalled magnetic coils) was placed on the abdomen outside of clothing in a configuration similar to that which occurs during colonoscopy. A monitoring read-out of ECG and EGM data was printed and a ScopeGuide (Olympus, version 2 software) was then connected " Fig. 2). During this time, the to the colonoscope for 2 minutes (● implanted cardiac device was monitored continuously for any interference using internal and external cardiac read-outs displayed on the PPM programmer device. The monitoring display was continuously reviewed by the investigator or pacing technician and digitally stored in the programmer device. If any interference was detected, the ECG/EGM was printed. After 2 minutes the ECG/EGM was printed for 5 seconds before the colonoscope was disconnected from the ScopeGuide, and for 5 seconds after disconnection. A full device check was then performed to determine whether any settings or thresholds had altered. End points were defined as reaching the recruitment target or detecting any interference with a device. An additional patient was recruited who had an implanted cardiac loop recorder (Reveal; Medtronic, Minneapolis, Minnesota, USA), which had been implanted to record any ECG abnormalities that could be causing unexplained syncope or palpitations. These devices use a single lead for ECG monitoring, and therefore may be more susceptible to electromagnetic interference. Possible interference was assessed using the same method as for other implanted cardiac devices.
Corbett Gareth D et al. Safety of ScopeGuide with implantable cardiac devices … Endoscopy 2014; 46: 135–138
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136
Original article
Table 1
Summary of baseline characteristics of recruited patients.
Sex, male / female, n
66 / 34
Age, mean ± SD (range), years
67.8 ± 11 (30 – 80)
Device type, n PPM
65
ICD
16
CRT
19
Pace only Defibrillator
9 10
Manufacturer, n Boston Scientific (PPM / ICD / CRT)
38 (22 / 7 / 9)
Medtronic (PPM / ICD / CRT)
57 (38 / 9 / 10)
Biotronik (PPM)
3 (3)
Sorin Group (PPM)
1 (1)
St. Jude Medical (PPM)
1 (1)
PPM, permanent pacemaker; ICD, implantable cardioverter defibrillator; CRT, cardiac resynchronization therapy.
Table 2
Indications for implantation of device.
Indications
Results
n
PPM
!
Heart block 1
37
A total of 230 patients were invited to participate and 100 provided written informed consent to participate in the study. " Table 1 shows the demographics of the patients, including ● the device type and device manufacturer. The indications for in" Table 2. serting the devices are shown in ● No interference was detected for any of the implanted cardiac devices tested. Specifically, there were no incidences of device dysfunction and no effects upon device settings. The 95 % confidence intervals for the probability of interference occurring are therefore 0 % – 3.6 %. The patient with the Reveal device also showed no interference.
Sinus node disease 2
16
Bradycardic atrial fibrillation
9
Syncope
3
ICD Dilated cardiomyopathy
7
Ischemic cardiomyopathy
4
Idiopathic ventricular fibrillation
3
Right ventricular dysplasia
1
Brugada syndrome
1
CRT – pace only Ischemic cardiomyopathy
5
Dilated cardiomyopathy
4
CRT – defibrillator
Discussion !
The number of patients receiving implantable cardiac devices every year is increasing [11]. This increase will inevitably mean that physicians and surgeons in noncardiac specialties will encounter such patients with increasing regularity. Similarly, the number of medical technologies in clinical use is also increasing. Because all electrical devices produce electromagnetic fields, they all have the potential to interfere with the functioning of implantable devices, even though the strength of the field produced – and thus the risk of interference – will vary substantially between devices. Due to the potential risk of interference, manufacturers of many medical devices, including ScopeGuide, have advised that they should not be used in patients with implantable devices. This is partly due to the fact that medical devices are classified by the Federal Communications Commission (USA) as Class A, a category that includes devices with much higher emission limits than those allowed in Class B, which is only for devices in domestic or residential use. Interestingly the emissions of ScopeGuide (9 – 11 kHz, field strength 70 dBuV/M at 3 meters) are below the Class B limits and are therefore equivalent to, or weaker than, many of those produced by domestic objects deemed safe for patients with implanted devices [14]. Indeed, while such manufacturer recommendations are understandable from a commercial point of view, it is important to realise that they are largely based on theoretical rather than a demonstrated risks of interference.
Dilated cardiomyopathy
5
Ischemic cardiomypathy
3
Hypertrophic cardiomyopathy
1
Idiopathic ventricular tachycardia
1
PPM, permanent pacemaker, ICD, implantable cardioverter defibrillator; CRT, cardiac resynchronization therapy. 1 Includes complete heart block, atrioventricular nodal block, and post atrioventricular nodal ablation. 2 Includes Sick Sinus Syndrome and symptomatic bradycardia.
In addition, over the past two decades, manufacturers of implantable cardiac devices have taken measures to reduce the potential for electromagnetic interference by adjusting the lead polarity, so that most devices now use a bipolar system in which the electrodes are closer to each other and within the heart resulting in a reduced chance of extraneous signals being interpreted as a cardiac event. Studies have attempted to define the real-life risks. One study from Finland [15] examined interference in PPMs and ICDs from a variety of high-strength magnetic field generators. This included a Helmholtz coil, allowing an accurately quantifiable electromagnetic field to be studied, but also an induction hob cooker which generates a much stronger magnetic field than the 9 – 11 kHz field produced by ScopeGuide and has an operating frequency of 48 kHz. Bipolar devices showed no interference in this study. Furthermore, other devices that generate comparable electromagnetic fields have been investigated and have been shown
Corbett Gareth D et al. Safety of ScopeGuide with implantable cardiac devices … Endoscopy 2014; 46: 135–138
This document was downloaded for personal use only. Unauthorized distribution is strictly prohibited.
Fig. 2 Picture demonstrating the experimental setup on participants in the pacemaker clinic. The colonoscope is coiled on the abdomen over the clothes to emulate a colonoscopy. A, colonoscope; B, ScopeGuide.
137
Original article
not to cause interference. In another study, walk-through airport metal detectors, which operate at a continuous frequency of 5 – 10 kHz, did not interfere with implantable cardiac devices in 348 patients [16]. An important caveat, however, is that there are reports of device dysfunction during surgical electrocautery, which resulted in end organ damage, and thus precautions should be taken when delivering endoscopic electrocautery in patients with implantable cardiac devices [17]. The current study aimed to determine whether a magnetic endoscope imager would cause interference with implantable cardiac devices. No interference between the electromagnetic field produced by ScopeGuide and the functioning of implantable cardiac devices was demonstrated, either ex vivo or in vivo, and even when the devices were set to maximal sensitivity. These data would suggest that ScopeGuide is safe for use in patients with implantable cardiac devices; however, there are some limitations to this study. Firstly, although the shape and proximity of the colonoscope to the implanted cardiac device will have accurately simulated what occurs during a colonoscopy, the study participants did not undergo a full colonoscopy. Furthermore, the exposure time was shorter than would occur during a colonoscopy. It will therefore be necessary to perform a further study involving patients undergoing colonoscopy, which on the basis of this work is now likely to be ethically acceptable. Secondly, despite not detecting any interference in a sample of 100 patients, it is possible that interference does occur at a lower incidence than was possible to detect with this sample size. Indeed, the 95 % confidence intervals (based on the number of episodes of interference detected and the sample size) would imply that there is up to a 3.6 % chance that interference might occur, which would reflect a sizeable risk. It is important to note, however, that in any study like this where no events are observed, the upper limit of the 95 % confidence interval will always be positive – even with very large sample sizes. Moreover, the original power calculation meant that if the true incidence of interference was 3 %, there was a 95 % chance that it would have been detected with a sample of this size. Accepting these limitations, we believe that ScopeGuide is likely to be safe for use in patients with implantable cardiac devices. This statement is based both on the data shown herein, but also on the number of domestic devices that generate stronger electromagnetic fields and which are deemed safe by regulatory agencies. Competing interests: None
Acknowledgment !
The authors would like to thank the cardiac physiologists at Cambridge University Hospitals NHS Foundation Trust (Lisa Johnson, Kate Sanders, Joana Teixeira, Sofia Pereira, Daniel Chan, Georgina Heard, and Viki Carpenter) for their assistance with this study.
References 1 Saunders BP, Bell GD, Williams CB et al. First clinical results with a real time, electronic imager as an aid to colonoscopy. Gut 1995; 36: 913 – 917 2 Williams CB, Saunders BP, Bell GD et al. Real-time magnetic three-dimensional imaging of flexible endoscopy. Gastrointest Endosc Clin N Am 1997; 7: 469 – 475 3 Shah SG, Brooker JC, Williams CB et al. Effect of magnetic endoscope imaging on colonoscopy performance: a randomised controlled trial. Lancet 2000; 356: 1718 – 1722 4 Shah SG, Pearson HJ, Moss S et al. Magnetic endoscope imaging: a new technique for localizing colonic lesions. Endoscopy 2002; 34: 900 – 904 5 Ellul P, Fogden E, Simpson C et al. Colonic tumour localization using an endoscope positioning device. Eur J Gastroenterol Hepatol 2011; 23: 488 – 491 6 Shergill AK, McQuaid KR, Deleon A et al. Randomized trial of standard versus magnetic endoscope imaging colonoscopes for unsedated colonoscopy. Gastrointest Endosc 2012; 75: 1031 – 1036 7 Olympus Endoscope Position Detecting Unit, UPD. ScopeGuide® Version 2 User Guide Tokyo: Olympus; 2009 8 Koller W, Pahwa R, Busenbark K et al. High-frequency/unilateral thalamic stimulation in the treatment of essential and parkinsonian tremor. Ann Neurol 1997; 42: 292 – 299 9 Zhang J, Chen JD. Pacing the gut in motility disorders. Curr Treat Options Gastroenterol 2006; 9: 351 – 360 10 Herbison GP, Arnold EP. Sacral neuromodulation with implanted devices for urinary storage and voiding dysfunction in adults. Cochrane Database Syst Rev 2009; 02: CD004202 11 Mond HG, Proclemer A. The 11th world survey of cardiac pacing and implantable cardioverter-defibrillators: calendar year 2009 – a World Society of Arrhythmia’s project. Pacing Clin Electrophysiol 2011; 34: 1013 – 1027 12 Trigano A, Blandeau O, Souques M et al. Clinical study of interference with cardiac pacemakers by a magnetic field at power line frequencies. J Am Coll Cardiol 2005; 45: 896 – 900 13 “Real Life Experience of interference with Implanted Heart Devices”. Warick, UK: National Grid; Available from: http://www.emfs.info/ The+Science/highfields/Pacemakers/experience/ Accessed: 6 August 2013 14 Code of Federal Regulations, Title 47 Telecommunications, Parts 0– 199, Federal Communications Commission Rules. USA: Federal Government; Available from: http://www.ecfr.gov/cgi-bin/text-idx? sid=64f63e21c14d853c79afa96fd333ff3e&c=ecfr&tpl=/ecfrbrowse/Title47/47tab_02.tpl Accessed: 27 Mar 2013 15 Tiikkaja M, Aro AL, Alanko T et al. Electromagnetic interference with cardiac pacemakers and implantable cardioverter-defibrillators from low-frequency electromagnetic fields in vivo. Europace 2013; 15: 388 – 394 16 Kolb C, Schmieder S, Lehmann G et al. Do airport metal detectors interfere with implantable pacemakers or cardioverter-defibrillators? J Am Coll Cardiol 2003; 41: 2054 – 2059 17 Corbett GD, Pugh PJ, Buttery P et al. Endoscopy and implantable devices. Frontline Gastroenterol 2012; 3: 72 – 75
Corbett Gareth D et al. Safety of ScopeGuide with implantable cardiac devices … Endoscopy 2014; 46: 135–138
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135
Safety of the colonoscope magnetic imaging device (ScopeGuide) in patients with implantable cardiac devices
Authors
Gareth D. Corbett1, Yean C. Lim1, James C. Lee1, Alexey Chernolesskiy1, Peter J. Pugh2, Ewen A. B. Cameron1
Institutions
1
submitted 9. June 2013 accepted after revision 4. November 2013
Bibliography DOI http://dx.doi.org/ 10.1055/s-0033-1359044 Endoscopy 2014; 46: 135–138 © Georg Thieme Verlag KG Stuttgart · New York ISSN 0013-726X Corresponding author Ewen A. B. Cameron, MD Box 293 Endoscopy Unit, Addenbrooke’s Hospital Cambridge, CB2 0QQ UK Fax: +44-1223-348729 ewen.cameron@addenbrookes. nhs.uk
Department of Gastroenterology, Cambridge University Hospitals NHS Foundation Trust, Cambridge, United Kingdom Department of Cardiology, Cambridge University Hospitals NHS Foundation Trust, Cambridge, United Kingdom
Background and study aims: Use of the colonoscope magnetic imaging device (ScopeGuide, Olympus Medical Systems, Tokyo, Japan) is currently contraindicated by the manufacturer for patients with implantable cardiac devices, a group of patients that is increasing annually along with the number of colonoscopies performed in the era of colorectal cancer screening. This is the first study to examine the safety of ScopeGuide in patients with permanent pacemakers, implantable cardioverter defibrillators, and cardiac resynchronization therapy. Patients and methods: Nonimplanted cardiac devices were exposed to the electromagnetic field of ScopeGuide ex vivo and assessed for evidence of interference or change in device settings. Following this, consecutive patients attending device check clinics were prospectively recruited and exposed to the ScopeGuide electromagnetic field.
After an initial device check, patients underwent continuous external cardiac monitoring and device interrogation while a colonoscope was placed on the abdomen over clothing and connected to ScopeGuide to simulate colonoscopy. Patients were monitored for 2 minutes to assess for any interference. ScopeGuide was then disconnected and devices were checked for any change in settings. Results: A total of 230 patients were invited to participate and 100 were recruited to the study. There was no evidence of interference on device leads or change in programming following exposure to the electromagnetic field generated by ScopeGuide. Conclusion: ScopeGuide does not appear to cause interference or change in settings and is therefore likely to be safe for use in patients with implantable cardiac devices.
Introduction
ognized by many endoscopists to be a useful adjunct to colonoscopy, even though it probably provides little benefit to expert colonoscopists [6]. ScopeGuide is currently contraindicated for use in patients with implantable electronic medical devices due to the electromagnetic field it generates [7]. Accordingly, this adjunct cannot be used in patients with permanent cardiac pacemakers (PPMs) or implantable cardioverter defibrillators (ICDs), nor in those with implantable infusion devices or neurostimulator devices that are used for Parkinson’s disease [8], gastric dysmotility [9], and bladder dysfunction [10]. Due to their increasing number, the patients for whom this is most likely to affect in daily practice are those with implantable cardiac devices. These devices include PPMs inserted for treatment of bradyarrhythmias, ICDs inserted for primary or secondary prophylaxis of life-threatening ventricular arrhythmias, and cardiac resynchronization therapy devices (CRT) for treatment of heart fail-
!
Colonoscopy is the gold standard investigation for suspected colorectal cancer and is used in many countries as a screening tool in at-risk age groups. This technique is technically challenging and can be uncomfortable for patients, particularly if loops form in the colonoscope. The colonoscope magnetic imaging device (ScopeGuide, Olympus Medical Systems, Tokyo, Japan) was developed in the 1990 s [1, 2] to aid colonoscopy training and to allow early detection of loops, and is being used with increasing frequency. This technology utilizes magnetic coils along the length of the colonoscope to provide a 3 D real-time graphic representation of the instrument, which facilitates the early recognition of loops and has been shown to reduce cecal intubation time and discomfort, and improve completion rates by trainee endoscopists [3]. It also allows the localization of colonic tumors with an accuracy equivalent to that of radiological imaging [4, 5]. ScopeGuide is therefore rec-
Corbett Gareth D et al. Safety of ScopeGuide with implantable cardiac devices … Endoscopy 2014; 46: 135–138
This document was downloaded for personal use only. Unauthorized distribution is strictly prohibited.
2
Original article
ure. In 2009, a worldwide survey showed that the number of implanted cardiac devices was increasing in almost all of the countries surveyed, with over 1 million devices inserted worldwide [11]. In such patients, the concern regarding ScopeGuide use is that the electromagnetic field produced might interfere with the medical device. This could manifest as device inhibition (e. g. PPMs failing to pace when they should), device dysfunction (e. g. inappropriate pacing with PPMs or inappropriate DC shock delivery with ICDs), or interference with device settings (e. g. returning them to the factory preset mode). This risk is theoretical as there have been no reports of cardiac device malfunction during endoscopic procedures. Moreover, the recommendation of the manufacturer (Olympus) is not based on evidence of actual interference (personal communication with Olympus). We therefore sought to assess the actual safety of using ScopeGuide in patients with implantable cardiac devices.
Methods
Fig. 1 Patient simulator device connected to ex vivo pacemaker, with colonoscope and ScopeGuide positioned to emulate a colonoscopy. A, pacemaker programmer; B, patient simulator; C, pacemaker with programmer wand; D, colonoscope; E, ScopeGuide.
!
Phase 1: ex vivo assessment of interference To assess whether the electromagnetic field created by ScopeGuide would interfere with cardiac device function, an ex vivo study was first performed as a proof of concept safety check. ScopeGuide was set up immediately adjacent to an examination trolley on which a connected colonoscope was placed. A PPM and an ICD (Boston Scientific, Massachusetts, USA) were in turn placed into the center of the coiled colonoscope. Each device was connected to a cardiac simulator device (used for cardiac device setup and maintenance) and wirelessly to a cardiac device programmer to provide monitoring and allow for setting adjustment " Fig. 1). For each device, monitoring of both electrocardiogra(● phy (ECG) and electrogram (EGM) from a simulated intracardiac rhythm was performed. The device settings were then incrementally increased to the most sensitive setting in order to maximize the potential for electromagnetic interference (PPM ventricular sensing threshold increased from 2.5 mV to 0.5mV in 0.25-mV increments; ICD ventricular sensing threshold reduced from 2.5 mV to 0.5 mV in 0.25-mV increments).
Phase 2: in vivo assessment of interference Based on the results of the Phase 1 experiments and further technical information relating to the radiofrequency emission of ScopeGuide obtained from the manufacturer, a noninvasive experiment was designed to determine whether ScopeGuide would cause cardiac device interference. Ethical approval was obtained from the East Cambridge Research and Ethics Committee (Reference 12 /EE0075) and the study was registered on ClinicalTrials. gov (NCT01825525). All patients were invited to participate by letter prior to routine appointments for a maintenance check on their implantable cardiac device, and all participating patients provided written informed consent. Included patients were aged between 18 and 80 years and had any type of implantable cardiac device (PPM, ICD or cardiac resynchronization therapy device) and were without any cognitive deficit. The results of a previous study that investigated the probability of PPM interference from magnetic fields at the frequencies generated by power lines [12] were used to determine the optimal sample size in the present study. In the previous study, the authors reported an incidence of interference of ~2 %. Importantly,
despite detecting this level of interference, the UK National Grid states that the Medicines and Health Regulatory Authority (London, UK) have received no reports of power lines interfering with PPMs in vivo, which makes it unlikely that any have occurred [13]. A total of 100 patients were sought for this experiment as this sample size would provide a 95 % probability of detecting interference if it were to occur at an incidence of 3 %. This was also an achievable number of patients given the size of our unit. To ensure each implanted device was functioning properly prior to exposure to ScopeGuide, each patient underwent a standard device interrogation to check for any abnormal rhythms or other problems that may have occurred since the previous interrogation. The thresholds from each pacing lead were also tested (the lowest output at which capture is achieved). After this device check, a colonoscope (Olympus H260-DL with preinstalled magnetic coils) was placed on the abdomen outside of clothing in a configuration similar to that which occurs during colonoscopy. A monitoring read-out of ECG and EGM data was printed and a ScopeGuide (Olympus, version 2 software) was then connected " Fig. 2). During this time, the to the colonoscope for 2 minutes (● implanted cardiac device was monitored continuously for any interference using internal and external cardiac read-outs displayed on the PPM programmer device. The monitoring display was continuously reviewed by the investigator or pacing technician and digitally stored in the programmer device. If any interference was detected, the ECG/EGM was printed. After 2 minutes the ECG/EGM was printed for 5 seconds before the colonoscope was disconnected from the ScopeGuide, and for 5 seconds after disconnection. A full device check was then performed to determine whether any settings or thresholds had altered. End points were defined as reaching the recruitment target or detecting any interference with a device. An additional patient was recruited who had an implanted cardiac loop recorder (Reveal; Medtronic, Minneapolis, Minnesota, USA), which had been implanted to record any ECG abnormalities that could be causing unexplained syncope or palpitations. These devices use a single lead for ECG monitoring, and therefore may be more susceptible to electromagnetic interference. Possible interference was assessed using the same method as for other implanted cardiac devices.
Corbett Gareth D et al. Safety of ScopeGuide with implantable cardiac devices … Endoscopy 2014; 46: 135–138
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136
Original article
Table 1
Summary of baseline characteristics of recruited patients.
Sex, male / female, n
66 / 34
Age, mean ± SD (range), years
67.8 ± 11 (30 – 80)
Device type, n PPM
65
ICD
16
CRT
19
Pace only Defibrillator
9 10
Manufacturer, n Boston Scientific (PPM / ICD / CRT)
38 (22 / 7 / 9)
Medtronic (PPM / ICD / CRT)
57 (38 / 9 / 10)
Biotronik (PPM)
3 (3)
Sorin Group (PPM)
1 (1)
St. Jude Medical (PPM)
1 (1)
PPM, permanent pacemaker; ICD, implantable cardioverter defibrillator; CRT, cardiac resynchronization therapy.
Table 2
Indications for implantation of device.
Indications
Results
n
PPM
!
Heart block 1
37
A total of 230 patients were invited to participate and 100 provided written informed consent to participate in the study. " Table 1 shows the demographics of the patients, including ● the device type and device manufacturer. The indications for in" Table 2. serting the devices are shown in ● No interference was detected for any of the implanted cardiac devices tested. Specifically, there were no incidences of device dysfunction and no effects upon device settings. The 95 % confidence intervals for the probability of interference occurring are therefore 0 % – 3.6 %. The patient with the Reveal device also showed no interference.
Sinus node disease 2
16
Bradycardic atrial fibrillation
9
Syncope
3
ICD Dilated cardiomyopathy
7
Ischemic cardiomyopathy
4
Idiopathic ventricular fibrillation
3
Right ventricular dysplasia
1
Brugada syndrome
1
CRT – pace only Ischemic cardiomyopathy
5
Dilated cardiomyopathy
4
CRT – defibrillator
Discussion !
The number of patients receiving implantable cardiac devices every year is increasing [11]. This increase will inevitably mean that physicians and surgeons in noncardiac specialties will encounter such patients with increasing regularity. Similarly, the number of medical technologies in clinical use is also increasing. Because all electrical devices produce electromagnetic fields, they all have the potential to interfere with the functioning of implantable devices, even though the strength of the field produced – and thus the risk of interference – will vary substantially between devices. Due to the potential risk of interference, manufacturers of many medical devices, including ScopeGuide, have advised that they should not be used in patients with implantable devices. This is partly due to the fact that medical devices are classified by the Federal Communications Commission (USA) as Class A, a category that includes devices with much higher emission limits than those allowed in Class B, which is only for devices in domestic or residential use. Interestingly the emissions of ScopeGuide (9 – 11 kHz, field strength 70 dBuV/M at 3 meters) are below the Class B limits and are therefore equivalent to, or weaker than, many of those produced by domestic objects deemed safe for patients with implanted devices [14]. Indeed, while such manufacturer recommendations are understandable from a commercial point of view, it is important to realise that they are largely based on theoretical rather than a demonstrated risks of interference.
Dilated cardiomyopathy
5
Ischemic cardiomypathy
3
Hypertrophic cardiomyopathy
1
Idiopathic ventricular tachycardia
1
PPM, permanent pacemaker, ICD, implantable cardioverter defibrillator; CRT, cardiac resynchronization therapy. 1 Includes complete heart block, atrioventricular nodal block, and post atrioventricular nodal ablation. 2 Includes Sick Sinus Syndrome and symptomatic bradycardia.
In addition, over the past two decades, manufacturers of implantable cardiac devices have taken measures to reduce the potential for electromagnetic interference by adjusting the lead polarity, so that most devices now use a bipolar system in which the electrodes are closer to each other and within the heart resulting in a reduced chance of extraneous signals being interpreted as a cardiac event. Studies have attempted to define the real-life risks. One study from Finland [15] examined interference in PPMs and ICDs from a variety of high-strength magnetic field generators. This included a Helmholtz coil, allowing an accurately quantifiable electromagnetic field to be studied, but also an induction hob cooker which generates a much stronger magnetic field than the 9 – 11 kHz field produced by ScopeGuide and has an operating frequency of 48 kHz. Bipolar devices showed no interference in this study. Furthermore, other devices that generate comparable electromagnetic fields have been investigated and have been shown
Corbett Gareth D et al. Safety of ScopeGuide with implantable cardiac devices … Endoscopy 2014; 46: 135–138
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Fig. 2 Picture demonstrating the experimental setup on participants in the pacemaker clinic. The colonoscope is coiled on the abdomen over the clothes to emulate a colonoscopy. A, colonoscope; B, ScopeGuide.
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Original article
not to cause interference. In another study, walk-through airport metal detectors, which operate at a continuous frequency of 5 – 10 kHz, did not interfere with implantable cardiac devices in 348 patients [16]. An important caveat, however, is that there are reports of device dysfunction during surgical electrocautery, which resulted in end organ damage, and thus precautions should be taken when delivering endoscopic electrocautery in patients with implantable cardiac devices [17]. The current study aimed to determine whether a magnetic endoscope imager would cause interference with implantable cardiac devices. No interference between the electromagnetic field produced by ScopeGuide and the functioning of implantable cardiac devices was demonstrated, either ex vivo or in vivo, and even when the devices were set to maximal sensitivity. These data would suggest that ScopeGuide is safe for use in patients with implantable cardiac devices; however, there are some limitations to this study. Firstly, although the shape and proximity of the colonoscope to the implanted cardiac device will have accurately simulated what occurs during a colonoscopy, the study participants did not undergo a full colonoscopy. Furthermore, the exposure time was shorter than would occur during a colonoscopy. It will therefore be necessary to perform a further study involving patients undergoing colonoscopy, which on the basis of this work is now likely to be ethically acceptable. Secondly, despite not detecting any interference in a sample of 100 patients, it is possible that interference does occur at a lower incidence than was possible to detect with this sample size. Indeed, the 95 % confidence intervals (based on the number of episodes of interference detected and the sample size) would imply that there is up to a 3.6 % chance that interference might occur, which would reflect a sizeable risk. It is important to note, however, that in any study like this where no events are observed, the upper limit of the 95 % confidence interval will always be positive – even with very large sample sizes. Moreover, the original power calculation meant that if the true incidence of interference was 3 %, there was a 95 % chance that it would have been detected with a sample of this size. Accepting these limitations, we believe that ScopeGuide is likely to be safe for use in patients with implantable cardiac devices. This statement is based both on the data shown herein, but also on the number of domestic devices that generate stronger electromagnetic fields and which are deemed safe by regulatory agencies. Competing interests: None
Acknowledgment !
The authors would like to thank the cardiac physiologists at Cambridge University Hospitals NHS Foundation Trust (Lisa Johnson, Kate Sanders, Joana Teixeira, Sofia Pereira, Daniel Chan, Georgina Heard, and Viki Carpenter) for their assistance with this study.
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