Does High-Power Computed Tomography Scanning Equipment Affect the Operation of Pacemakers?

Interference of cardiac implantable electronic devices and computed tomography imaging in the current era with a phantom model

INTRODUCTION

Cardiac implantable electronic devices are used in patients with cardiac rhythm disorders. Computed tomography irradiation is not prohibited for patients with cardiac implantable electronic devices, despite adverse events being reported. Hence, appropriate preparation and knowledge are required before computed tomography irradiation can be carried out in these patients. Since there is limited knowledge or literature about the influence of computed tomography irradiation in cases with recent cardiac implantable electronic devices, we aimed to evaluate the adverse events and elucidate the necessary and sufficient safety measures associated with this therapy.

METHODS AND RESULTS

We placed cardiac implantable electronic devices on an anthropomorphic phantom model and observed their electrical activity in electrograms, while various protocols of computed tomography irradiation were implemented and adverse events evaluated. Oversensing with pauses of up to 3.2 s was observed in standard computed tomography protocols, but ventricular tachyarrhythmia or other clinically significant events could not be confirmed. Oversensing with pauses of up to 8.0 s was observed and ventricular tachyarrhythmia was detected in the maximum-dose protocols. However, treatments such as antitachycardia pacing or shock therapy for ventricular tachyarrhythmia were not observed because of their absence.

CONCLUSION

Computed tomography irradiation for patients using cardiac implantable electronic devices is highly unlikely to cause clinically significant adverse events with the device settings and computed tomography protocols currently being used. Changing or monitoring the device settings routinely before computed tomography irradiation is not necessarily required for most patients.

Impact of X-Ray Exposure From Computed Tomography on Wearable Insulin Delivery Devices

BACKGROUND

To investigate the impact of radiation exposure from a computed tomography (CT) scanner on the functional integrity of a wearable insulin delivery system.

METHODS

A total of 160 Omnipods and four personal diabetes managers (PDMs) were evenly divided into four groups: (1) control group (no radiation exposure), (2) typical radiation exposure group, (3) 4× typical radiation exposure group, and (4) scatter radiation group. Pods were attached to an anthropomorphic torso phantom on the abdomen (direct irradiation) or shoulder (scatter radiation) region. A third-generation dual-source CT scanner was used to scan the pods using either a typical exposure (used for routine CT abdominal study of a median size patient) or 4× typical exposure. A manufacturer-recommended 20-step functionality test was performed for all 160 Omnipods.

RESULTS

The radiation dose (measured in volume CT Dose index) was 16 mGy for a typical exposure, and 64 mGy for 4× typical exposure. The scatter radiation is less than 0.1 mGy. All Pods passed the functionality test except one pod in the scatter radiation group, which sounded an alarm due to occlusion. The blockage to the fluid was due to a kink in the soft cannula, a mechanical issue not caused by the radiation exposure.

CONCLUSIONS

This study suggests X-ray exposure levels used in radiological imaging procedures do not negatively impact the functional integrity of Omnipods. This finding may support the potential for the manufacturer to remove the warning that patients should remove the Pod for X-ray imaging procedures, which will have a huge impact on patient care.

Risk of Cardiac Implantable Electronic Device Malfunctioning During Pencil Beam Proton Scanning in an In Vitro Setting

PURPOSE

Cardiac implantable electronic devices (CIED) are sensitive to scattered secondary neutrons from proton beam irradiation. This experimental in vitro study investigated risk of CIED errors during pencil beam proton therapy.

METHODS AND MATERIALS

We used 62 explanted CIEDs from 4 manufacturers; 49 CIEDs were subjected to a simulated clinical protocol with daily 2 Gy relative biological effectiveness fractions prescribed to the phantom. Devices were located at 3 different lateral distances from the spread-out Bragg peak to investigate the risk of permanent or temporary device errors. Additionally, 13 devices with leads connected were monitored live during consecutive irradiations to investigate the risk of noise, over- or undersense, pace inhibition, and inappropriate shock therapy.

RESULTS

We detected 61 reset errors in 1728 fractions, and all except 1 CIED were reprogrammed to normal function. All, except 1 reset, occurred in devices from the same manufacturer. These were successfully reprogrammed to normal function. The 1 remaining CIED was locked in permanent safety mode. Secondary neutron dose, as estimated by Monte Carlo simulations, was found to significantly increase the odds of CIED resets by 55% per mSv. Clinically significant battery depletion was observed in 5 devices. We observed no noise, over- or undersense, pace inhibition, or inappropriate shock therapy during 362 fractions of live monitoring.

CONCLUSIONS

Reprogrammable CIED reset was the most commonly observed malfunction during proton therapy, and reset risk depended on secondary neutron exposure. The benefits of proton therapy are expected to outweigh the risk of CIED malfunctioning for most patients.

Initial testing of pegfilgrastim (Neulasta Onpro) on-body injector in multiple radiological imaging environments

Purpose

An increasing number of implantable or external devices can impact whether patients can receive radiological imaging examinations. This study examines and tests the Neulasta (pegfilgrastim) Onpro on‐body injector in multiple imaging environments.

Methods

The injector was analyzed for four imaging modalities with testing protocols and strategies developed for each modality. In x‐ray and computed tomography (CT), scans with much higher exposure than clinical protocols were performed with the device attached to an anthropomorphic phantom. The device was monitored until the completion of drug delivery. For magnetic resonance imaging (MRI), the device was assessed using a hand‐held magnet and underwent the magnetically induced displacement testing in a 1.5T clinical MRI scanner room. For ultrasound, magnetic field changes were measured around an ultrasound scanner system with three transducers.

Results

For x‐ray and CT no sign of device error was identified during or after the high radiation exposure scans. Drug delivery was completed at expected timing with expected volume. For MRI the device showed significant attractive force towards the hand‐held magnet and a 50‐degree deflection angle at 50 cm from the opening of the scanner bore. No further assessment from the gradient or radiofrequency field was deemed necessary. For ultrasound the maximum magnetic field change from baseline was measured to be +11.7 μT in comparison to +74.2 μT at 4 inches from a working microwave.

Conclusions

No device performance issue was identified under the extreme test conditions in x‐ray or CT. The device was found to be MR Unsafe. Magnetic field changes around an ultrasound system met the limitation set by manufacture. Patient ultrasound scanning is considered safe as long as the transducers do not inadvertently loosen the device.

Effect of X-ray dose rates higher than 8 Gy/min on the functioning of cardiac implantable electronic devices

Direct irradiation may cause malfunctioning of cardiac implantable electronic devices (CIEDs). Therefore, a treatment plan that does not involve direct irradiation of CIEDs should be formulated. However, CIEDs may be directly exposed to radiation because of the sudden intrafractional movement of the patient. The probability of CIED malfunction reportedly depends on the dose rate; however, reports are only limited to dose rates ≤8 Gy/min. The purpose of this study was to investigate the effect of X-ray dose rates >8 Gy/min on CIED function. Four CIEDs were placed at the center of the radiation field and irradiated using 6 MV X-ray with flattening filter free (6 MV FFF) and 10 MV X-ray with flattening filter free (10 MV FFF). The dose rate was 4-14 Gy/min for the 6 MV FFF and 4-24 Gy/min for 10 MV FFF beams. CIED operation was evaluated with an electrocardiogram during each irradiation. Three CIEDs malfunctioned in the 6 MV FFF condition, and all four CIEDs malfunctioned in the 10 MV FFF condition, when the dose rate was >8 Gy/min. Pacing inhibition was the malfunction observed in all four CIEDs. Malfunction occurred simultaneously along with irradiation and simultaneously returned to normal function on stopping the irradiation. An X-ray dose rate >8 Gy/min caused a temporary malfunction due to interference. Therefore, clinicians should be aware of the risk of malfunction and manage patient movement when an X-ray dose rate >8 Gy/min is used for patients with CIEDs.

Management of radiotherapy patients with implanted cardiac pacemakers and defibrillators: A Report of the AAPM TG-203†

Managing radiotherapy patients with implanted cardiac devices (implantable cardiac pacemakers and implantable cardioverter-defibrillators) has been a great practical and procedural challenge in radiation oncology practice. Since the publication of the AAPM TG-34 in 1994, large bodies of literature and case reports have been published about different kinds of radiation effects on modern technology implantable cardiac devices and patient management before, during, and after radiotherapy. This task group report provides the framework that analyzes the potential failure modes of these devices and lays out the methodology for patient management in a comprehensive and concise way, in every step of the entire radiotherapy process.

Potential effects of low-dose average CT on cardiac implantable electronic devices

BACKGROUND

Average CT has been shown to be more accurate than conventional helical CT in quantitation of the PET data. The risk of CT irradiation of a cardiac implantable electronic device (CIED) causing an adverse event is low and is generally outweighed by the clinical benefit of a medically indicated examination. However, irradiation of CIED over one breath cycle in cine CT scan for average CT could impose risks on a patient who is pacing dependent. The purpose of this study was to demonstrate that low-dose average CT can be safe for CIED.

METHODS

A Medtronic CIED of model Protecta VR was submerged in a saline bath for a series of 4-s cine CT scans on a GE CT scanner programmed to deliver a 2-cm-wide radiation at a dose rate of 0.9 to 41.2 mGy/s to the CIED. The number of over-sensings was recorded as the interference of radiation to the CIED.

RESULTS

Dose rates ≥ 1.9 mGy/s caused over-sensing. The higher the dose rate, the more over-sensings there were. The lowest dose rate of 0.9 mGy/s did not cause any over-sensing.

CONCLUSIONS

Low-dose average CT at 0.9 mGy/s can be safe for a CIED patient who is pacing dependent.

Do we need to establish guidelines for patients with neuromodulation implantable devices, including spinal cord stimulators undergoing nonspinal surgeries?

Background:

Spinal cord stimulation is currently approved to treat chronic intractable pain of the trunk and limbs. However, such implantable electronic devices are vulnerable to external electrical currents and magnetic fields. Within the hospitals and modern operating rooms (ORs), there is an abundance of electrical devices and other types of equipment that could interfere with such devices. Despite the increasing number of patients with neuromodulation implantable devices, there are no written guidelines available or consensus of cautions for such patients undergoing unrelated surgery.

Case Descriptions:

A 60-year-old female with a permanent St. Jude's spinal cord stimulator (SCS) presented for open total abdominal hysterectomy. Both the anesthesia and gynecology staffs were aware of the device presence, but were unaware of any precautions regarding intraoperative management. The device was found to be nonmagnetic resonance imaging compatible, and bipolar cautery was used instead of monopolar cautery. A 59-year-old female with a 9-year-old permanent Medtronic SCS, presented for right total hip arthroplasty. The device was switched off prior to entering the OR, bipolar cautery was used, and grounding pads were placed away from her battery site. In each case, the manufacturer's representative was contacted preoperative. Both surgeries proceeded uneventfully.

Conclusions:

The Food and Drug Administration safety information manual warns about the use of diathermy, concomitant implanted stimulation devices, lithotripsy, external defibrillation, radiation therapy, ultrasonic scanning, and high-output ultrasound, all of which can lead to permanent implant damage if not turned off prior to undertaking procedures. Lack of uniform guidelines makes intraoperative management, as well as remote anesthesia care of patients with previously implanted SCSs unsafe.

Spinal cord stimulation: a review of the safety literature and proposal for perioperative evaluation and management

BACKGROUND CONTEXT

There is currently no consensus on appropriate perioperative management of patients with spinal cord stimulator implants. Magnetic resonance imaging (MRI) is considered safe under strict labeling conditions. Electrocautery is generally not recommended in these patients but sometimes used despite known risks.

PURPOSE

The aim was to discuss the perioperative evaluation and management of patients with spinal cord stimulator implants.

STUDY DESIGN

A literature review, summary of device labeling, and editorial were performed, regarding the safety of spinal cord stimulator devices in the perioperative setting.

METHODS

A literature review was performed, and the labeling of each Food and Drug Administration (FDA)-approved spinal cord stimulation system was reviewed. The literature review was performed using PubMed and the FDA website (www.fda.gov).

RESULTS

Magnetic resonance imaging safety recommendations vary between the models. Certain systems allow for MRI of the brain to be performed, and only one system allows for MRI of the body to be performed, both under strict labeling conditions. Before an MRI is performed, it is imperative to ascertain that the system is intact, without any lead breaks or low impedances, as these can result in heating of the spinal cord stimulation (SCS) and injury to the patient. Monopolar electrocautery is generally not recommended for patients with SCS; however, in some circumstances, it is used when deemed required by the surgeon. When cautery is necessary, bipolar electrocautery is recommended. Modern electrocautery units are to be used with caution as there remains a risk of thermal injury to the tissue in contact with the SCS. As with MRI, electrocautery usage in patients with SCS systems with suspected breaks or abnormal impedances is unsafe and may cause injury to the patient.

CONCLUSIONS

Spinal cord stimulation is increasingly used in patients with pain of spinal origin, particularly to manage postlaminectomy syndrome. Knowledge of the safety concerns of SCS and appropriate perioperative evaluation and management of the SCS system can reduce risks and improve surgical planning.

Dosimetric review of cardiac implantable electronic device patients receiving radiotherapy

A formal communication process was established and evaluated for the management of patients with cardiac implantable electronic devices (CIEDs) receiving radiation therapy (RT). Methods to estimate dose to the CIED were evaluated for their appropriateness in the management of these patients. A retrospective, institutional review board (IRB) approved study of 69 patients with CIEDs treated with RT between 2005 and 2011 was performed. The treatment sites, techniques, and the estimated doses to the CIEDs were analyzed and compared to estimates from published peripheral dose (PD) data and three treatment planning systems (TPSs) — UMPlan, Eclipse's AAA and Acuros algorithms. When measurements were indicated, radiation doses to the CIEDs ranged from 0.01–5.06 Gy. Total peripheral dose estimates based on publications differed from TLD measurements by an average of 0.94 Gy (0.05–4.49 Gy) and 0.51 Gy (0–2.74 Gy) for CIEDs within 2.5 cm and between 2.5 and 10 cm of the treatment field edge, respectively. Total peripheral dose estimates based on three TPSs differed from measurements by an average of 0.69 Gy (0.02–3.72 Gy) for CIEDs within 2.5 cm of the field edge. Of the 69 patients evaluated in this study, only two with defibrillators experienced a partial reset of their device during treatment. Based on this study, few CIED‐related events were observed during RT. The only noted correlation with treatment parameters for these two events was beam energy, as both patients were treated with high‐energy photon beams (16 MV). Differences in estimated and measured CIED doses were observed when using published PD data and TPS calculations. As such, we continue to follow conservative guidelines and measure CIED doses when the device is within 10 cm of the field or the estimated dose is greater than 2 Gy for pacemakers or 1 Gy for defibrillators.

PACS number: 87.55.N‐

Cardiac CT: Imaging of and Through Cardiac Devices

For patients with cardiac devices, cardiac computed tomography (CT) remains the mainstay for imaging due to its superior resolution as compared with echocardiography and nuclear studies and no contraindication to metal as with cardiac magnetic resonance imaging. This review focuses on the evaluation and pitfalls of coronary arterial imaging in patients with devices, such as pacemakers, implantable defibrillators, cardiac resynchronization therapy (CRT), as well as complications such as lead perforation and safety concerns of CT interference. We discuss both pre- and post-procedural CRT assessment for coronary venous imaging and pre-procedural myocardial scar assessment to localize regions of scar and peri-infarct zone to facilitate ventricular tachycardia ablation in patients with devices. We describe potential new research on dyssynchrony and integration with myocardial scar and site of latest activation for patients with or being considered for CRT. We detail the utility of CT for the assessment of proper function and complications in patients with left ventricular assist device implantation.

Proton dose perturbations caused by high-voltage leads from implanted cardioverter defibrillators

An increasing number of patients undergoing proton radiotherapy have cardiac implantable electrical devices (CIEDs). We recently encountered a situation in which a high‐voltage coil on a lead from an implanted cardiac defibrillator was located within the clinical treatment volume for a patient receiving proton radiotherapy for esophageal cancer. To study the effects of the lead on the dose delivery, we placed a high‐Z CIED lead at both the center and the distal edge of a clinical spread‐out Bragg peak (SOBP) in a water phantom, in both a stationary position and with the lead moving in a periodic pattern to simulate cardiorespiratory movement. We then calculated planned doses using a commercial proton treatment planning system (TPS), and compared them with the doses delivered in the phantom, measured using radiographic film. Dose profiles from TPS‐calculated and measured dose distributions showed large pertubrations in the delivered proton dose in the vicinity of the CIED lead when it was not moving. The TPS predicted perturbations up to 20% and measurements revealed perturbations up to 35%. However, the perturbations were less than 3% when the lead was moving. Greater dose perturbations were seen when the lead was placed at the distal edge of the SOBP than when it was placed in the center of the SOBP. We conclude that although cardiorespiratory motion of the lead mitigates some of the perturbations, the effects of the leads should be considered and steps taken to reduce these effects during the treatment planning process.

PACS numbers: 87.55.D‐,87.55.ne, 87.85.M

Electromagnetic interference and implanted cardiac devices: the medical environment (part II)

Electromagnetic interference produced by medical equipment can interact with implanted cardiac devices such as pacemakers and implantable cardioverter-defibrillators. The most commonly observed interaction is in the operating room with electrosurgery. The risk of interactions can often be mitigated by close communication between the cardiac-device specialist and the anesthesiology/surgical team to develop a patient-specific strategy that accounts for factors such as type of device, type of surgery, and whether the patient is pacemaker dependent. Although magnetic resonance imaging should generally not be used in patients with implanted cardiac devices, several published guidelines provide strategies and recommendations for managing risks if magnetic resonance imaging is required with no suitable diagnostic alternatives. Other common sources of electromagnetic interference in the medical environment are ionizing radiation and left ventricular assist devices.

Computed tomography in patients with cardiac pacemakers: difficulties and solutions

The presence of cardiac pacemaker systems may significantly limit interpretation of multi-slice computed tomography (MSCT) images. In 80 patients (45 men; aged 69.5 ± 13.4) with previously implanted anti-arrhythmic devices, a 64-slice CT (Aquilion-64) was performed. In 61 patients (76.3%), ECG gating was used (coronaries visualization) and in 19 patients (23.7%) without ECG gating (not coronaries visualization). In all 19 patients without ECG gating MSCT images were diagnostic. In 37 (60.6%) patients of 61, there was no problem with gating process and image quality was diagnostic. In 24 (39.4%) with visible spikes in the ECG-gating group, there were difficulties in differentiating the R spike from an artificial spike (unipolar pacing) by MSCT software. In 15 patients (24.6%) after reprogramming, it was possible to obtain good quality images. In nine (14.7%) patients, it was not possible to reprogram devices due to old unipolar leads, but in two cases (3.3%), ECG gating was corrected manually and good image quality was obtained. In seven (11.5%) patients, it was not possible to perform ECG gating. The ECG gating process was identified as the main cause of the imaging problems. Bipolar leads working as bipolar pacing seem to be necessary to perform MSCT with ECG gating. A unipolar system lead may cause serious problems with reconstructions.

X-ray radiation causes electromagnetic interference in implantable cardiac pacemakers

BACKGROUND

X-rays are not thought to cause electromagnetic interference (EMI) in implantable cardiac pacemakers. However, x-ray radiation during computed tomography (CT) scanning has been reported to cause EMI in some implantable cardiac pacemakers. The objectives of this study were to identify the location within the pacemakers where x-ray radiation causes EMI and to investigate the association of EMI with the x-ray radiation conditions.

METHODS

We verified the location where x-ray radiation caused EMI using a CT scanner and conventional radiographic x-ray equipment. An inhibition test and an asynchronous test were performed using five types of implantable cardiac pacemakers.

RESULTS

X-ray radiation inhibited the pacing pulses of four types of implantable cardiac pacemakers when the body of each implantable cardiac pacemaker, containing a complementary metal-oxide semiconductor (CMOS), was scanned using a CT scanner. We confirmed that x-ray-induced EMI depends on the x-ray radiation conditions, that is, the tube voltage, tube current, x-ray dose, and direction of x-ray radiation, as well as the sensing thresholds of the implantable cardiac pacemakers.

CONCLUSIONS

X-ray radiation caused EMI in some implantable cardiac pacemakers, probably because the CMOS component was irradiated. The occurrence of EMI depended on the pacemaker model, sensing threshold of the pacemaker, and x-ray radiation conditions.

Establishing radiation therapy treatment planning effects involving implantable pacemakers and implantable cardioverter-defibrillators

Recent improvements to the functionality and stability of implantable pacemakers and cardioverter‐defibrillators involve changes that include efficient battery power consumption and radiation hardened electrical circuits. Manufacturers have also pursued MRI‐compatibility for these devices. While such newer models of pacemakers and cardioverter‐defibrillators are similar in construction to previously marketed devices – even for the recent MRI‐compatible designs currently in clinical trials – there is increased interest now with regard to radiation therapy dose effects when a device is near or directly in the field of radiation. Specifically, the limitation on dose to the device from therapeutic radiation beams is being investigated for a possible elevation in limiting dose above 200 cGy. We present here the first‐ever study that evaluates dosimetric effects from implantable pacemakers and implantable cardioverter‐defibrillators in high energy X‐ray beams from a medical accelerator. Treatment plan simulations were analyzed for four different pacemakers and five different implantable cardioverter‐defibrillators and intercompared with direct measurements from a miniature ionization chamber in water. All defibrillators exhibited the same results and all pacemakers were seen to display the same consequences, within only a a±1.8% deviation for all X‐ray energies studied. Attenuation, backscatter, and lateral scatter were determined to be −13.4%, 2.1% and 1.5% at 6 MV, and −6.1%, 3.1% and 5.1% at 18 MV for the defibrillator group. For the pacemaker group, this research showed results of −15.9%, 2.8% and 2.5% at 6 MV, and −9.4%, 3.4% and 5.7% at 18 MV, respectively. Limited results were discovered from scattering processes through computer modeling. Strong verification from measurements was concluded with respect to simulating attenuation characteristics. For IP and ICD leads, measured dose changes were less than 4%, existing as attenuation processes only, and invariant with regard to X‐ray energy.

PACS number: 87.53.Bn, 87.53.Dq, 87.53.Tf, 87.66.Jj

Computed Tomography Scan and ICD Interaction

Although it has been considered a safe procedure, computed tomography scanning uses high doses of radiation and can cause malfunctioning in those patients with ICD when the radiation is directly incident on the device. We present a case of ventricular oversensing during a thoracic computed tomography.

Safety and imaging quality of MRI in pediatric and adult congenital heart disease patients with pacemakers

BACKGROUND

Magnetic resonance imaging (MRI) is a standard of care in evaluating many disease processes. Given concerns about device damage or movement, programming changes, lead heating, inappropriate pacing, and image artifact, MRI is contraindicated in pacemaker patients. Despite this, studies have demonstrated safety and efficacy of MRI in adults with acquired heart disease and endocardial pacing leads. We sought to evaluate MRI use in congenital heart disease (CHD) patients with predominantly epicardial pacing leads.

METHODS

From July 2007 to October 2008, MRI (1.5 Tesla) was performed in 11 patients without alternative imaging modality who were not pacemaker dependent or possessing abandoned leads. Pacing was disabled during MRI. An electrophysiologist monitored electrocardiogram and hemodynamic parameters throughout each study. Device and lead function were evaluated before and after MRI, and at subsequent clinic visits.

RESULTS

Eleven MRIs (four cardiac, seven noncardiac) were performed in eight patients. Mean patient age was 16.5 +/- 9.2 years (range 1.7-24.5) with five patients under the age of 16 years. Diagnoses included structural CHD in six patients and long QT syndrome and congenital heart block in one each. There were three dual- and five single- (three atrial, two ventricular) chamber devices, two endocardial, and nine epicardial leads. No inappropriate pacing or significant change in generator or lead parameters was noted. All MRI studies were of diagnostic quality.

CONCLUSION

Diagnostic quality MRI can be performed safely in nonpacemaker-dependent CHD patients with predominantly epicardial leads. Further studies will define safe practice measures in this population, as well as in CHD patients with pacemaker dependency.

[Effect of diagnostic X-rays on implantable cardiac pacemakers and implantable cardioverter defibrillators, and its management]

The effects of diagnostic X-rays on implantable cardiac pacemakers and implantable cardioverter defibrillators (ICDs) were investigated. A total of 33 pacemakers from six manufacturers and nine ICDs from four manufacturers were irradiated using several X-ray units (plain X-ray diagnostic unit, under-table system fluoroscopy unit, over-table system fluoroscopy unit, biplane cardiac digital angiography unit, DSA unit and cone-beam CT unit). No systematic reset phenomena were observed in any pacemakers and ICDs under the X-ray irradiation. Nevertheless, over-sensing associated with the lack of a few pulses was observed in three of 33 pacemakers under radiation exposure. It has been proven that diagnostic X-rays might affect pacemaker function. Since the duration of the over-sensing under the radiation was very short and included transient episodes, this sensing failure, therefore, induced by radiation exposure would not affect the health of pacemaker recipients. ICDs were not affected by radiation exposure at a clinical dose. It is recommended that caution be exercised in direct irradiation to the pacemaker. Using a copper sheet of 2.0 mm thickness or more prevented over-sensing of pacemakers in the present study, especially when serial X-ray exposures were used with an over-table fluoroscopy system or cone-beam CT unit.

[Experimental study of the influence on pacemakers of X-rays from angiocardiography equipment]

We performed an experimental study of the influence on pacemakers (PM) of X-rays from the angiocardiography equipment. (1) We used one PM of DDD mode in this study. (2) The PM was irradiated under two exposure levels: one the standard dose and the other the maximum dose in the angiocardiography study situation. (3) We set the pacing lead wires to the bilateral atria and ventricles in Irnich's human body model. (4) We set two irradiation fields, one with a lead block on the PM and the other without the lead block. The result showed that when the PM was included in the irradiation field and the exposure level was of the maximum dose, the influence of irradiation on the PM was that of level 2 as classified by a research report by the Ministry of Internal Affairs and Communications. The absorbed dose of the PM was 93.4 mGy under these conditions. We confirmed that radiation dose does not affect a pacemaker with pacing lead wire. However, it acts on the generator of the PM owing to the direct photoelectric effect. When there were many dose rates (or total radiation dose), an obstacle occurred.

Effects of CT Irradiation on Implantable Cardiac Rhythm Management Devices1

PURPOSE

To prospectively measure the response of a variety of models of implantable cardiac rhythm management devices (ICRMDs) to the radiation delivered by computed tomography (CT), for both maximum and typical dose levels.

MATERIALS AND METHODS

Twenty-one ICRMDs (13 pacemakers, eight cardioverter-defibrillators) manufactured by Medtronic (Minneapolis, Minn) were exposed to ionizing radiation from CT systems in both spiral and dynamic acquisition modes at maximum and typical dose levels. Devices were monitored during exposure to check for any operational abnormalities and were interrogated after exposure to check for any residual abnormalities. Total radiation dose and peak dose rate were measured, and the volume CT dose index was recorded.

RESULTS

Oversensing was observed in 20 of 21 devices at maximum doses and in 17 of 20 devices at typical doses. Oversensing most often manifested as inhibition, although it occasionally manifested as tracking or safety pacing. Two devices inhibited for more than 4 seconds in spiral mode at clinical dose levels. Oversensing was transient and ceased as soon as the device stopped moving through the x-ray beam or the beam was turned off. The partial electrical reset (PER) safety feature was activated in two models, InSync 8040 and Thera DR. With the exception of PER, programming was not altered. Effects occurred only if the x-ray beam passed directly over the ICRMD.

CONCLUSION

CT irradiation at typical clinical doses results in oversensing of ICRMDs in the majority of devices tested, although the identified effects were predominantly transient.