- Email: [email protected]
Cosmic radiation: Not science fiction, but clinical reality
EDITORIAL COMMENTARY
Cosmic radiation: Not science fiction, but clinical reality Deepak Bhakta, MD, Lynne D. Foreman, RN From the Krannert Institute of Cardiology, Indiana University School of Medicine, Indianapolis, Indiana. Since its conception in the 1960s and the first successful implant in 1980, the implantable cardioverter-defibrillator (ICD) has become a cornerstone in preventing sudden death in high-risk populations.1 The widespread acceptance of ICDs in clinical practice has been accompanied by a gradual paradigm shift in how such therapy is applied. Its earliest uses targeted survivors of cardiac arrest due to ventricular arrhythmias. However, in recent years it has been used in a broader, primary preventative role, that is, in asymptomatic individuals with only clinical markers of elevated arrhythmic risk.2– 6 As a result, the frequency of ICD placement has increased steadily over the past decade to include this larger cohort of patients.7 This greater number of implanted devices increases the potential for unfavorable device-related occurrences (e.g., inappropriate shock, ICD and/or lead malfunction, electromagnetic interference, and anxiety due to device recall) that may lead to adverse consequences in previously asymptomatic patients. Although the lifesaving benefit of ICD placement is evident in this group, its impact on lifestyle and quality of life must not be ignored.8 –10 In this issue of Heart Rhythm, Ferrick et al11 present a series of three ICD recipients who experienced programming reset during air travel. Information provided by each device’s event log clearly confirms that each event occurred during flight. As in-flight use of electronic devices is generally restricted, the authors have invoked naturally occurring cosmic radiation as the source of these programming disruptions. Cosmic radiation previously has been raised as an unavoidable source of device reset, albeit to a much smaller degree than with iatrogenic sources (as with radiation therapy linear accelerators).12,13 As mentioned by the authors, exposure to naturally occurring cosmic radiation is greater at higher altitudes, a point that underscores the relevance of the current series. As the population of ICD recipients expands, so too will the number of individuals traveling by air, possibly leading to a greater-than-expected number of resets due to cosmic radiation.14 Device malfunction due to any cause (including reset) may result in unfavorable sequelae in a given patient. In the present series, device reset resulted in automatic reprogramming of pacing mode in one patient, possibly causing sympAddress reprint requests and correspondence: Dr. Deepak Bhakta, Krannert Institute of Cardiology, 1800 North Capitol Avenue, Indianapolis, Indiana 46202. E-mail address: [email protected].
toms due to loss of AV synchrony and rate-adaptive pacing. A second subject expressed considerable anxiety upon learning of his device’s reset (device alarming occurred in these two cases, promptly signaling these patients of an alert condition). In each case, device reset resulted in reversion to rudimentary programming, allowing protection against ventricular arrhythmias and bradycardia. Potentially life-saving therapy was not compromised in any example. However, as the ICD population further diversifies, individualized device programming must be emphasized, and even seemingly minor alterations in device programming may carry significant consequences. Fortunately, the adverse effects of cosmic radiation on implantable devices appear to be a rare phenomenon, although the series presented by Ferrick et al nevertheless raises several intriguing issues. It is interesting that, in their practice, three resets were observed over a course of 2 years, possibly indicating an already increasing frequency of such events. It also is curious that these events were observed in ICDs only, without any reported disruptions in pacemakers. All three incidents occurred on transcontinental flights, highlighting the importance of altitude and duration of exposure in inducing these resets. Although uncommon, the potential interaction between cosmic radiation and implanted devices must not be ignored. Complete elimination may not be possible, but manufacturers have installed mechanisms to assess device memory integrity and determine the presence of memory upset, leading to device reset and alert condition. Efforts to further study the overall frequency of this phenomenon clearly will be hindered by unpredictability and infrequency of events. However, the advent of home ICD monitoring may make such surveillance more practical from an investigational and a clinical standpoint. Further study also may help elucidate the perceived difference of susceptibility to cosmic radiation between pacemakers and ICDs. Until its effects are further characterized, however, it may be prudent to advise ICD patients anticipating air travel of the effects of cosmic radiation on their device, particularly when a prolonged flight is planned. A change in symptoms attributable to device reprogramming or, certainly, audible or sensory device alarming following flight must be brought to a physician’s attention, with performance of in-office follow-up or home ICD monitoring. With the convenience of home ICD
1547-5271/$ -see front matter © 2008 Heart Rhythm Society. All rights reserved.
doi:10.1016/j.hrthm.2008.05.005
Bhakta and Foreman
Editorial Commentary
interrogation, routine home evaluation following air travel may be reasonable. Finally, patients may be reassured that although these interactions may not be completely preventable, in general they result only in temporary “soft” resets that do not affect the lifesaving features of their ICD.
References 1. Mirowski M, Mower M, Stawean W. Standby automatic defibrillator, an approach to prevention of sudden cardiac death. Arch Intern Med 1970;29:158 – 161. 2. Bardy G, Lee K, Mark D, et al. Amiodarone or an implantable cardioverterdefibrillator for congestive heart failure. N Engl J Med 2005;352:225–237. 3. Buxton A, Lee K, DiCarlo L, et al. Electrophysiologic testing to identify patients with coronary artery disease who are at risk for sudden death. N Engl J Med 2000;342:1937–1945. 4. AVID Investigators. A comparison of anti-arrhythmic-drug therapy versus implantable defibrillators in patients resuscitated from near-fatal ventricular arrhythmias. N Engl J Med 1997;337:1576 –1583. 5. Moss A, Hall W, Cannom D, et al. Improved survival with an implanted defibrillator in patients with coronary disease at risk for ventricular arrhythmias. N Engl J Med 1996;335:1933–1940.
1205 6. Moss A, Zareba W, Hall W, et al. Prophylactic implantation of a defibrillator in patients with myocardial infarction and reduced ejection fraction. N Engl J Med 2002;346:877– 883. 7. Maisel W, Megan M, Zuckerman B, et al. Pacemaker and ICD generator malfunctions JAMA 2006;295:1901–1906. 8. Leosdottir M, Sigurdsson E, Reimarsdottir G, et al. Health-related quality of life of patients with implantable cardioverter defibrillators compared with that of pacemaker recipients. Europace 2006;8:168 –174. 9. Noyes K, Corona E, Zwanziger J, et al. Health-related quality of life consequences of implantable cardioverter defibrillators: results from MADIT II. Med Care 2007;45:377–385. 10. Groeneveld P, Matta M, Suh J, et al. Quality of life among implantable cardioverter-defibrillator recipients in the primary prevention therapeutic era. Pacing Clin Electrophysiol 2007;30:463– 471. 11. Ferrick A, Bernstein N, Aizer A, et al. Cosmic radiation induced software electrical resets in ICDs during air travel. Heart Rhythm 2008;5:1201–1203. 12. Bradley P, Normand E. Single event upsets in implantable cardioverter defibrillators. IEEE Trans Nucl Sci 1998;45(Pt 1):2929 –2940. 13. Wilkinson J, Bounds C, Brown T, et al. Cancer-radiotherapy equipment as a cause of soft errors in electronic equipment. IEEE Trans Device Mater Reliab 2005;5:449 – 451. 14. Lim M. Cosmic rays: are air crews at risk? Occupat Environ Med 2002;59:428 – 432.
Cosmic radiation: Not science fiction, but clinical reality Deepak Bhakta, MD, Lynne D. Foreman, RN From the Krannert Institute of Cardiology, Indiana University School of Medicine, Indianapolis, Indiana. Since its conception in the 1960s and the first successful implant in 1980, the implantable cardioverter-defibrillator (ICD) has become a cornerstone in preventing sudden death in high-risk populations.1 The widespread acceptance of ICDs in clinical practice has been accompanied by a gradual paradigm shift in how such therapy is applied. Its earliest uses targeted survivors of cardiac arrest due to ventricular arrhythmias. However, in recent years it has been used in a broader, primary preventative role, that is, in asymptomatic individuals with only clinical markers of elevated arrhythmic risk.2– 6 As a result, the frequency of ICD placement has increased steadily over the past decade to include this larger cohort of patients.7 This greater number of implanted devices increases the potential for unfavorable device-related occurrences (e.g., inappropriate shock, ICD and/or lead malfunction, electromagnetic interference, and anxiety due to device recall) that may lead to adverse consequences in previously asymptomatic patients. Although the lifesaving benefit of ICD placement is evident in this group, its impact on lifestyle and quality of life must not be ignored.8 –10 In this issue of Heart Rhythm, Ferrick et al11 present a series of three ICD recipients who experienced programming reset during air travel. Information provided by each device’s event log clearly confirms that each event occurred during flight. As in-flight use of electronic devices is generally restricted, the authors have invoked naturally occurring cosmic radiation as the source of these programming disruptions. Cosmic radiation previously has been raised as an unavoidable source of device reset, albeit to a much smaller degree than with iatrogenic sources (as with radiation therapy linear accelerators).12,13 As mentioned by the authors, exposure to naturally occurring cosmic radiation is greater at higher altitudes, a point that underscores the relevance of the current series. As the population of ICD recipients expands, so too will the number of individuals traveling by air, possibly leading to a greater-than-expected number of resets due to cosmic radiation.14 Device malfunction due to any cause (including reset) may result in unfavorable sequelae in a given patient. In the present series, device reset resulted in automatic reprogramming of pacing mode in one patient, possibly causing sympAddress reprint requests and correspondence: Dr. Deepak Bhakta, Krannert Institute of Cardiology, 1800 North Capitol Avenue, Indianapolis, Indiana 46202. E-mail address: [email protected].
toms due to loss of AV synchrony and rate-adaptive pacing. A second subject expressed considerable anxiety upon learning of his device’s reset (device alarming occurred in these two cases, promptly signaling these patients of an alert condition). In each case, device reset resulted in reversion to rudimentary programming, allowing protection against ventricular arrhythmias and bradycardia. Potentially life-saving therapy was not compromised in any example. However, as the ICD population further diversifies, individualized device programming must be emphasized, and even seemingly minor alterations in device programming may carry significant consequences. Fortunately, the adverse effects of cosmic radiation on implantable devices appear to be a rare phenomenon, although the series presented by Ferrick et al nevertheless raises several intriguing issues. It is interesting that, in their practice, three resets were observed over a course of 2 years, possibly indicating an already increasing frequency of such events. It also is curious that these events were observed in ICDs only, without any reported disruptions in pacemakers. All three incidents occurred on transcontinental flights, highlighting the importance of altitude and duration of exposure in inducing these resets. Although uncommon, the potential interaction between cosmic radiation and implanted devices must not be ignored. Complete elimination may not be possible, but manufacturers have installed mechanisms to assess device memory integrity and determine the presence of memory upset, leading to device reset and alert condition. Efforts to further study the overall frequency of this phenomenon clearly will be hindered by unpredictability and infrequency of events. However, the advent of home ICD monitoring may make such surveillance more practical from an investigational and a clinical standpoint. Further study also may help elucidate the perceived difference of susceptibility to cosmic radiation between pacemakers and ICDs. Until its effects are further characterized, however, it may be prudent to advise ICD patients anticipating air travel of the effects of cosmic radiation on their device, particularly when a prolonged flight is planned. A change in symptoms attributable to device reprogramming or, certainly, audible or sensory device alarming following flight must be brought to a physician’s attention, with performance of in-office follow-up or home ICD monitoring. With the convenience of home ICD
1547-5271/$ -see front matter © 2008 Heart Rhythm Society. All rights reserved.
doi:10.1016/j.hrthm.2008.05.005
Bhakta and Foreman
Editorial Commentary
interrogation, routine home evaluation following air travel may be reasonable. Finally, patients may be reassured that although these interactions may not be completely preventable, in general they result only in temporary “soft” resets that do not affect the lifesaving features of their ICD.
References 1. Mirowski M, Mower M, Stawean W. Standby automatic defibrillator, an approach to prevention of sudden cardiac death. Arch Intern Med 1970;29:158 – 161. 2. Bardy G, Lee K, Mark D, et al. Amiodarone or an implantable cardioverterdefibrillator for congestive heart failure. N Engl J Med 2005;352:225–237. 3. Buxton A, Lee K, DiCarlo L, et al. Electrophysiologic testing to identify patients with coronary artery disease who are at risk for sudden death. N Engl J Med 2000;342:1937–1945. 4. AVID Investigators. A comparison of anti-arrhythmic-drug therapy versus implantable defibrillators in patients resuscitated from near-fatal ventricular arrhythmias. N Engl J Med 1997;337:1576 –1583. 5. Moss A, Hall W, Cannom D, et al. Improved survival with an implanted defibrillator in patients with coronary disease at risk for ventricular arrhythmias. N Engl J Med 1996;335:1933–1940.
1205 6. Moss A, Zareba W, Hall W, et al. Prophylactic implantation of a defibrillator in patients with myocardial infarction and reduced ejection fraction. N Engl J Med 2002;346:877– 883. 7. Maisel W, Megan M, Zuckerman B, et al. Pacemaker and ICD generator malfunctions JAMA 2006;295:1901–1906. 8. Leosdottir M, Sigurdsson E, Reimarsdottir G, et al. Health-related quality of life of patients with implantable cardioverter defibrillators compared with that of pacemaker recipients. Europace 2006;8:168 –174. 9. Noyes K, Corona E, Zwanziger J, et al. Health-related quality of life consequences of implantable cardioverter defibrillators: results from MADIT II. Med Care 2007;45:377–385. 10. Groeneveld P, Matta M, Suh J, et al. Quality of life among implantable cardioverter-defibrillator recipients in the primary prevention therapeutic era. Pacing Clin Electrophysiol 2007;30:463– 471. 11. Ferrick A, Bernstein N, Aizer A, et al. Cosmic radiation induced software electrical resets in ICDs during air travel. Heart Rhythm 2008;5:1201–1203. 12. Bradley P, Normand E. Single event upsets in implantable cardioverter defibrillators. IEEE Trans Nucl Sci 1998;45(Pt 1):2929 –2940. 13. Wilkinson J, Bounds C, Brown T, et al. Cancer-radiotherapy equipment as a cause of soft errors in electronic equipment. IEEE Trans Device Mater Reliab 2005;5:449 – 451. 14. Lim M. Cosmic rays: are air crews at risk? Occupat Environ Med 2002;59:428 – 432.