This provides an overview of the publications exploring the effects of x-ray irradiation from CT imaging on implantable pacemakers and implantable cardioverter defibrillators (ICD) that we used to develop our recommendations.
- In 2006, Yamaji et. al. reported transient malfunctions such as asynchronous pacing and oversensing in six out of 11 patients of their study that received diagnostic chest scans. 
- Between 2006 and 2014, the medical device industry has published a number of patents describing mitigation techniques of CT radiation and implantable medical device interference. [2-5]
- In 2007, McCollough et. al. evaluated 13 pacemakers and eight ICDs from Medtronic affixed on an anthropomorphic phantom and scanned with various clinical CT protocols (coronary angiography, coronary calcium scoring, pulmonary embolism detection and chest examination) that directly irradiate typical implantation sites. The authors observed that under typical clinical doses, a number of the devices experienced pacing inhibition and tracking, depending on the examination. When scanning using the maximum possible doses, one case of power-on reset was observed. They stressed that interference occurred only when the scanner directly irradiated the device and that inhibition was shorter when the patient table moved faster through the x-ray beam. The primary cause of interference was the use of a higher dose delivery rate, not a higher absolute dose. In this study, high doses delivered at lower rates did not trigger any events.
- In 2008 Oda et al. followed McCollough’s approach to repeat the analysis on 33 pacemakers from six manufacturers and on nine ICDs from four manufacturers, all affixed to an anthropomorphic phantom. Short episodes of oversensing were observed in three pacemakers, but none of the ICDs appeared to be affected. 
- In 2008, the medical device industry published a number of white papers [8, 9] describing the effects of CT radiation on pacemakers and ICDs.
- In 2009, Porres et al. published a case report where the ICD of a pacing dependent patient recorded oversensing that mimicked ventricular tachyarrhythmia during thoracic CT scanning. The oversensing was associated with capacitor charging and inappropriate inhibition of needed ventricular pacing but no reported patient symptoms. Porres reported that because the oversensing was brief, no shock was delivered. 
- In 2010, Hirose et al. experimentally identified that the electronic component most likely responsible for the pacemaker interactions with x rays was the ECG amplifier and that it was only affected when the pacemaker was positioned directly in the x ray beam. 
- In 2011, the Heart Rhythm Society published a document on the perioperative management of patients with pacemakers, ICDs and arrhythmia monitors, which included some information on interactions between these devices and diagnostic radiation from CT. 
- In 2014, Hussein et al. reported on a 10-year retrospective review of patient records of 241 patients with ICDs and 145 patients with pacemakers that received CT scans for medical conditions that would typically expose the implant site to radiation.  Their study did not identify any clinically significant adverse events reported in patients’ records. Specifically, they did not identify any reported deaths, bradycardia or tachycardia requiring the termination of the CT scan or an immediate intervention, unplanned hospital admissions, reprogramming of the device, inappropriate lCD shocks, or device replacement or revision thought to be related to radiation exposure from CT imaging. Some of the limitations of the 2014 Huseein et al. study were that it did not attempt to determine whether oversensing or pacing inhibition had actually occurred in any of the patients. Furthermore, the authors did not report dose rate or total dose information on any of the scans.
In conclusion, although it is possible that CT x-rays directly irradiating the electronics of implantable pacemakers or ICDs can cause electronic interference, the probability that this interference can cause clinically significant adverse events is extremely low. The probability of x-ray electromagnetic interference is lower when radiation dose and particularly the radiation dose rate are reduced. Interference can be completely avoided when the implantable device is outside of the primary x-ray beam of the CT scanner.
 Yamaji, S., et al., “Does High-Power Computed Tomography Scanning Equipment Affect the Operation of Pacemakers?,” Circulation Journal 70:190-197 (2006)
 Clement W. et al., “Methods and apparatus for reducing deleterious effects of x-ray radiation upon implantable medical device circuitry,” US Patent Application No: US 20060241398 A1
 Clement W. et al., “Methods and apparatus for reducing spurious signals in implantable medical devices caused by x-ray radiation,” US Patent Application No: US 20060224064 A1, 2006
 Roberts J. P. et al., “Radiation-based timer for implantable medical devices,” US Patent Application No: WO 2010098980 A1, 2011
 Stevenson R. A. et al., “Ionizing radiation-protected active implantable medical device,” US Patent Application No: US 8694102 B2, 2014
 McCollough C., et al, “Effects of CT Irradiation on Implantable Cardiac Rhythm Management Devices,” Radiology 243 (3):766-774 (2007).
 N. Oda, H. Nakajima, H. Abe, S. Koyama, S. Kakeda, and Y. Kourogi, “Effect of diagnostic X-rays on implantable cardiac pacemakers and implantable cardioverter defibrillators, and its management,” Nippon Hoshasen Gijutsu Gakkai Zasshi, vol. 64, no. 7, pp. 805–813, 2008.
 Boston Scientific, Computed Tomography (CT) Scanning and Implantable Pacemakers and Defibrillators, 2008.
 St. Jude Medical, Diagnostic Radiation and Implantable Cardiac Rhythm Devices, 2008
 Porres J. M., et al., “Computed Tomography Scan and ICD Interaction,” Case Reports in Medicine, vol. 2009, Article ID 189429, 3 pages, 2009.
 Hirose M., et al., “X-ray radiation causes electromagnetic interference in implantable cardiac pacemakers.” Pacing and Clinical Electrophysiology. 2010; 33:1174-1181
 Crossley G. H., et al., “The Heart Rhythm Society (HRS)/American Society of Anesthesiologists (ASA) Expert Consensus Statement on the Perioperative Management of Patients with Implantable Defibrillators, Pacemakers and Arrhythmia Monitors: Facilities and Patient Management,” Heart Rhythm, Vo. 8, No. 7, pp 1114-1151, 2011
 Hussein A. A., et al., “Safety of Computed Tomography in Patients With Cardiac Rhythm Management Devices: Assessment of the U.S. Food and Drug Administration Advisory in Clinical Practice.” J Am Coll Cardiol. 2014; 63(17):1769-1775.