Effects of scatter radiation on ICD and CRT function

Background: Effects of direct radiation on implantable cardiac devices have been well studied. However, the effects of scatter radiation are not as clear. Recommendations on management of patients with implantable cardiac devices undergoing radiotherapy are based on limited studies mostly involving pacemakers. We sought to elucidate the effects of scatter radiation on implantable cardioverter-defibrillators (ICDs) and cardiac resynchronization therapy (CRT)-ICDs.
Methods: We exposed 12 ICDs and eight CRT-ICDs to 400 cGy of scatter radiation from a 6-MV photon beam. Devices were programmed with nominal parameters and interrogated prior to radiation, after each fraction, upon completion of the radiation course and again 1 week later. A retrospective review of patients undergoing radiotherapy at the Mayo Clinic–Rochester between 2002 and 2007 in whom the device was outside the radiation field was also performed. There were 13 patients with devices undergoing radiotherapy during this time period, 12 of whom were interrogated prior to and after radiation.
Results: Interrogation reports were reviewed for device reset or parameter changes. There was no evidence of reset or malfunction during or after radiation. Also, no episodes of device reset, inappropriate sensing or therapy, or changes in programmed parameters were found in our review of patients undergoing radiotherapy.
Conclusions: Device reset or malfunction associated with scatter radiation likely represents an unpredictable, rare occurrence. While we see no clear contraindication to radiotherapy in patients with ICDs or CRT-ICDs, precautions should be taken to avoid direct radiation exposure and to closely evaluate patient outcomes before and after the radiation course.     

Use of a transurethral microwave thermotherapeutic device with permanent pacemakers and implantable defibrillators

OBJECTIVE: To determine whether a device (Urologix Targis system) used for transurethral microwave treatment interferes with sensing, pacing, and arrhythmia detection by permanent pacemakers and implantable cardioverter-defibrillators (ICDs). METHODS: We tested 13 pacemakers in both bipolar and unipolar sensing configurations and 8 ICDs in vitro. Pacemakers and ICDs were programmed to their most sensitive settings. Energy outputs of the microwave device were typical of those used clinically. The probe of the microwave device was anchored 1.2 cm from the pacemaker or ICD being tested. RESULTS: No sensing, pacing, or arrhythmic interactions were noted with any ICD or any pacemaker programmed to the bipolar configuration. One pacemaker (Guidant Vigor 1230) showed intermittent tracking when programmed to the unipolar configuration. CONCLUSIONS: Most patients with permanent pacemakers or ICDs can safely undergo transurethral microwave therapy using the device tested. Pacemakers and ICDs should be programmed to the bipolar configuration (if available) during therapy. The pacemaker or ICD should be interrogated before and after therapy to determine whether programming changes occurred as a result of treatment. However, our findings suggest that this is unlikely.     

An Unusual Source of Electromagnetic Interference: A Device–Device Interaction

Introduction: Implantable cardioverter‐defibrillators (ICDs) are susceptible to oversensing of extracardiac signals, also known as electromagnetic interference (EMI). We report a case of an unusual source of electrical interference of only the high voltage (HV) impedance measurement in the Teligen? ICD (Boston Scientific, St. Paul, MN, USA) caused by electrical interference from an electrosurgical generator with an electrocautery patch located in close proximity to the ICD pulse generator. Method and Results: A patient underwent an uneventful implant of a Boston Scientific Teligen? 100 ICD. Once the device was inserted in a pocket, interrogation of the device repeatedly demonstrated HV electrode impedance measurements between <20 and 40Ωand noise only on the HV electrode. A new lead and generator were implanted without a change in the interrogation results. The erroneous measurements of HV impedance were caused by a combination of the close proximity of the electrocautery patch to the ICD generator. The continuous low‐amplitude current emitted by the contact quality monitoring system of the electrosurgical cautery generator interfered with an equally weak current delivered through the lead by the device to measurement HV impedance. The Medtronic Virtuoso? (Medtronic Inc., Minneapolis, MN, USA) ICD and the St. Jude Medical Current? DR (St. Jude Medical, St. Paul, MN, USA) ICD were not affected by the patch due to greater magnitude of current delivered by the device to measure HV electrode impedance. Conclusion: It is important that the operator must be aware of any potential source of EMI, as it may affect the device and require immediate troubleshooting. Failure to recognize this interaction may result in inappropriate and unnecessary pulse generator replacement. (PACE 2010; 994–998)     

Electromagnetic Interference (EMI) and arrhythmic events in ICD patients undergoing gastrointestinal procedures

BACKGROUND: The objective was to determine the effect of electromagnetic interference (EMI) in patients undergoing gastrointestinal endoscopy. The implantable cardioverter-defibrillator (ICD) is the primary therapeutic modality for patients at risk for sudden cardiac death. One potential problem with ICDs is interactions with electrical devices and medical procedures causing EMI or triggering arrhythmic events. Endoscopy frequently employs electrocautery (EC) for diagnosis and treatment of gastrointestinal diseases. Current guidelines advise inactivating ICDs before any surgical procedure. There is limited information on management of ICDs during endoscopy with or without EC. We prospectively evaluated patients with ICDs undergoing endoscopic procedures at our institution. METHODS AND RESULTS: Forty-one ICD patients underwent 52 gastrointestinal endoscopies over 17 months. The mean age of the population was 66 years (51-83). There were 28 men and 13 women. Thirteen patients had single chamber devices, 25 had dual chamber devices, and 2 had biventricular ICDs. The mean tachyarrhythmia detection rate programmed was 164.7 bpm (125-188). Eighteen procedures (43.9%) required biopsy, coagulation, or polypectomy. Of these, 10 (55%) required the use of EC. Only unipolar EC with mean current 19.6 mA was used. All ICDs were programmed to detection-only with therapies off. Sensitivity was left at nominal programmed settings. Post procedure interrogation showed no detection of EMI or tachyarrhythmic events. CONCLUSIONS: Our study shows no EMI or arrhythmic events triggered during endoscopic procedures in patients with pectorally implanted transvenous ICDs. Routine practice of programming ICDs off for gastrointestinal procedures may not be necessary. However, larger studies are needed before change in current recommendations.     

Deactivating implanted cardiac devices in terminally ill patients: practices and attitudes

Background: Clinicians may receive requests to deactivate pacemakers and implantable cardioverter-defibrillators (ICDs) in terminally ill patients.
Methods: We describe practices and attitudes regarding deactivation of pacemakers and ICDs in terminally ill patients among physicians, nurses, and others who manage treatment of patients with implanted cardiac devices and among field representatives of device manufacturers. A Web-based survey was provided to Heart Rhythm Society members and to representatives of two manufacturers of implantable cardiac devices. Measurements were the answers of 787 respondents.
Results: Of the respondents, 86.8% reported involvement in requests for ICD deactivation and 77.6% reported involvement in pacemaker deactivation (P < 0.001). Having cared for a terminally ill patient for whom the respondent or a physician had ordered device deactivation was common (95.4% for ICDs vs 84.8% for pacemakers; P < 0.001). Having personally deactivated a device was also common (92.4% for ICDs vs 76.6% for pacemakers; P < 0.001). More respondents said they were comfortable with personally deactivating an ICD than deactivating a pacemaker (56.7% for ICDs vs 34.4% for pacemakers; P < 0.001). Respondents reported that the industry representative is the individual who deactivates the device most of the time (59.3% for ICDs and 49.7% for pacemakers).
Conclusions: Deactivation of implanted cardiac devices in terminally ill patients is common. Practices and attitudes associated with pacemaker deactivation differ significantly from those associated with ICD deactivation. Professional groups should develop guidelines for managing requests for implanted cardiac device deactivation and should clarify the role of device industry representatives in these deactivations.     

Electromagnetic Interference from a Muscle Stimulation Device Causing Discharge of an Implantable Cardioverter Defibrillator: Epicardial Bipolar and Endocardial Bipolar Sensing Circuits Are Compared

This case report is about two patients with two different types of ICDs who underwent electrical muscle stimulation (EMS) therapy. In one patient with an ICD that has epicardial screw-in bipolar sensing leads, electromagnetic interference (EMI) from the EMS device caused the delivery of an inappropriate ICD discharge. In a second patient with an ICD with endocardial true bipolar sensing, there was no evidence of EMI during the EMS therapy despite all of our attempts to reproduce it. The sensing circuits in the two different ICDs are compared.     

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.     

Physician management of pacemaker and implantable cardioverter defibrillator advisories

This study was designed to determine how physicians manage pacemaker (PM) and implantable cardioverter defibrillator (ICD) recalls and safety alerts (collectively "advisories") and to determine which factors influence physicians' clinical decisions. Although PM and ICD advisories affected over 500,000 patients in the past decade, physician clinical management of advisory devices has not been well studied. Advisories continue to occur frequently and are increasing in number and rate. Five-hundred physician members of the North American Society of Pacing and Electrophysiology (NASPE) were randomly surveyed by mail and were asked to make clinical recommendations regarding the management of various PM and ICD advisory scenarios. One hundred sixty-two physicians (32%) responded to the survey (cardiac electrophysiologist 69%, general cardiologist 22%, surgeon 6%, and other 3%). There was consensus among physicians regarding the management of some PM and ICD advisories but not others. Factors associated with a higher likelihood of physician recommendation for prophylactic advisory device replacement include: ICD implanted for secondary prevention (vs primary prevention, P < 0.001), pacemaker dependence (P < 0.001), prior appropriate ICD therapy (P < 0.001), higher likelihood of device malfunction (P < 0.001), and physician in practice <10 years (P = 0.02). The number of devices implanted or followed per year and physician specialty had no impact on advisory device management. Physician consensus exists regarding the management of some PM and ICD advisories and can be used to guide clinical practice. Substantial differences of opinion, however, are present regarding the management of many other advisories. Evidence based guidelines incorporating the indication for device implantation and the likelihood of device malfunction would greatly facilitate clinical management of PM and ICD advisory devices.     

Resetting of DDD Pacemakers Due to EMI

Multiprogrammable pacemakers have long been subject to inappropriate reprogramming and electromagnetic interference (EMI). A limited clinical experience with DDD pacing systems precludes the significance of such phenomena in these units. Since August 1981, in a series of 140 DDD systems, certain units demonstrated consistent and reproducible resetting to the back-up modes caused by electrocautery. One unit was permanently reset to the VOO mode. These observations suggest the need for renewed caution at the time of surgery; they also underscore the importance of a thorough understanding of any DDD system and careful follow-up so that such phenomena will not be misinterpreted as pacemaker failure, resulting in erroneous pacemaker removal.     

Radiofrequency Ablation of Atrial Flutter and Atrial Tachycardias in Patients with Permanent Indwelling Catheters

The presence of chronic indwelling leads in the area targeted for RF ablation may pose a technical challenge and reduce the chance of success of the ablation. In addition, application of lesions in close proximity to pacemaker leads or other permanent catheters could affect their function. Fourteen patients referred for RF ablation of atrial flutter/fibrillation and atrial tachycardia, who had a permanent dual chamber pacemaker (10 patients), ICD (1 patient), or both (3 patients) were studied to assess the safety, efficacy, and effects of the ablative procedure on device function. Lead impedance, R and P wave amplitude, and pacing threshold of the defibrillator and pacemaker were measured before and after ablation. The procedure was successful in all patients. In one patient who underwent both atrial flutter and atrial fibrillation ablation, the atrial pacing threshold increased from 1.0 preablation to 2.0 V postablation. No P wave was detectable after ablation. In another patient, the P wave amplitude went from 4.0 to 2.0 mV postablation. In both patients the device converted to the power reset mode. No changes were observed in the remaining patients. Postablation defibrillator testing showed no malfunction. Follow-up reinterrogation of the devices revealed no alterations. In conclusion: (1) RF ablation of atrial flutter and/or tachycardia is feasible even in patients with multiple chronic atrial and ventricular indwelling catheters; and (2) RF applications in close proximity of defibrillator and pacing catheters does not appear to alter their function unless lesions are produced in the area surrounding the distal pacing electrode.     

Environmental Electromagnetic Interference from Electronic Article Surveillance Devices: Interactions with an ICD

A patient with an implantable cardioverter defibrillator (ICD) experienced an inappropriate firing while in close proximity to an electronic article surveillance (EAS) device. Testing revealed the ICD was able to detect high frequency "noise" when close to the EAS device. ICD patients may need counseling to avoid close contact with such devices.     

Outcome of magnetic resonance imaging (MRI) in selected patients with implantable cardioverter defibrillators (ICDs)

OBJECTIVE: To determine if simple strategies used to safely scan pacemaker patients could be applied to implantable cardioverter defibrillator (ICD), patients undergoing MRI allowing ICD patients to undergo MRI as well. INTERVENTIONS: Screening, reprogramming, and monitoring strategies were used to facilitate MRI. RESULTS: Seven patients underwent eight MRI scans at 1.5 T. Post-MRI, all devices demonstrated no change in pacing, sensing, impedances, charge times, or battery status. The patient undergoing a lumbar spine scan experienced a "power-on-reset" of his ICD without permanent impairment of his device. CONCLUSION: Scanning of ICD patients might be performed if appropriate reprogramming and monitoring is implemented.     

Dual Device Therapy in the Setting of Changing ICD Technology: Device-Device Interaction Revisited

This case report concerns an adverse device-device interaction between a replacement ICD and a dual chamber rate responsive pacemaker. It was observed that subtle changes in the design of sensing circuits between an older first-generation ICD and the newer third-generation ICD device led to unexpected and dramatic changes in the interactive behavior of a dual device system. The new ICD was connected to chronically implanted hardware. The sensing behavior of the newer ICD included a shorter time constant in the decay of the automatic gain control function, resulting in triple sensing of both the atrial and ventricular paced stimuli and the evoked QRS complex. Physicians should be aware of new design changes in the future so as to anticipate such interactions. In the setting of rapidly changing technology, extra caution must be exercised when choosing to implant two devices in the same patient.     

Interactions Between Transvenous Nonthoracotomy Cardioverter Defibrillator Systems and Permanent Transvenous Endocardial Pacemakers

Limited information is available regardIng potential adverse Interactions between transvenous nonthoracotomy cardioverter defibrillators and pacemakers. We describe our experience with 37 patients who have undergone successful Implantation of both a transvenous defibrillator and pacemaker. The patients’mean age was 64 ± 12,9 years. Thirty-three were male and four were female. The mean LVEF wos 30.8%±11.8%, The indications for pacemaker implantation included sick sinus syndrome in 13 patients, complete heart block in 15 patients, sinus brady-cardia secondary to medications In 8 patients, and neurocardlogenlc syncope In 1 patient. The Indications for Insertion of a defibrillator Included medically refractory VT in 27 patients and sudden cardiac death in 10 patients. Twenty-three patients received an Endotak lead and 14 patients received o Transvene lead. Eighteen patients had a pacemaker prior to an ICD, 14 patients had an ICD prior to a pacemaker, and 4 patients had both devices placed simultaneously. Interaction was evaluated at Implant of the second device and 1–3 days after both devices were placed. Detection of VF/VT was analyzed during asynchronous pacing (DOO/VOO) with maximum pacing output. In addition, in six patients, DFT was determined before and after pacemaker implantation. In 14 patients (38%), device interactions that could not always be optimally corrected were observed. In five patients, the pacemaker was reset to the “noise reversion” mode after high energy ICD discharge, Oversensing of atrial pacemaker stimuli resulted in inappropriate ICD firings in four patients. This wos observed only with a specific device ond could not be prevented by atriol leod repositioning in two of them, but required reprogramming of the pacemaker to the VVImode. An increase in DFT was observed in five patients who had a pacemaker implanted after on ICD. Compared with previously published studies, a greater frequency of tronsvenous ICD and pacemaker Interactions were observed. Considering that almost 50% of the patients already have o pacemaker ot the time of ICD Implant, the ovalloblllty of deflbrlllotors with dual chamber pocing capability will not eliminate the potential for this problem.     

Initial experience with an active-fixation defibrillation electrode and the presence of nonphysiological sensing

Nonphysiological sensing by a pacing and defibrillation electrode may result in inappropriate defibrillator discharges and/or inhibition of pacing. Active-fixation electrodes may be more likely to sense diaphragmatic myopotentials because of the protrusion of the screw for fixation. In addition, the movement of the fixation screw in an integrated bipolar lead system could also result in inappropriate sensing. This may be increasingly important in patients who are pacemaker dependent because the dynamic range of the autogain feature of these devices is much more narrow. Five of 15 consecutive patients who received a CPI model 0154 or 0155 active-fixation defibrillation electrode with an ICD system (CPI Ventak A V3DR model 1831 or CPI Ventak VR model 1774 defibrillator) are described. In 2 of the 15 patients, nonphysiological sensing appearing to be diaphragmatic myopotentials resulted in inappropriate defibrillator discharges. Both patients were pacemaker dependent. Changes in the sensitivity from nominal to less sensitive prevented inappropriate discharges. In one patient, discreet nonphysiological sensed events with the electrogram suggestive of ventricular activation was noted at the time of implantation. This was completely eliminated by redeployment of the active-fixation lead in the interventricular septum. In two other patients, discreet nonphysiological sensed events resulted in intermittent inhibition of ventricular pacing after implantation. These were still seen in the least sensitive autogain mode for ventricular amplitude. These were not seen on subsequent interrogation 1 month after implantation. Increased awareness of nonphysiological sensing is recommended. The CPI 0154 and 0155 leads seem to be particularly prone to this abnormality. Particular attention should be made when deploying an active-fixation screw for an integrated bipolar lead. This increased awareness is more important when a given individual is pacemaker dependent, which may warrant DFT testing in a least or less sensitive mode in these patients.     

Left Ventricular Mechanical Assist Devices and Cardiac Device Interactions: An Observational Case Series

Background: Nonpulsatile left ventricular assist devices (LVADs) are increasingly used for treatment of refractory heart failure. A majority of such patients have implanted cardiac devices, namely implantable cardioverter-defibrillators (ICDs) or cardiac resynchronization therapy-pacemaker (CRT-P) or cardiac resynchronization therapy-defibrillator (CRT-D) devices. However, potential interactions between LVADs and cardiac devices in this category of patients remain unknown.
Methods: We reviewed case records and device logs of 15 patients with ICDs or CRT-P or CRT-D devices who subsequently had implantation of a VentrAssist LVAD (Ventracor Ltd., Chatswood, Australia) as destination therapy or bridge to heart transplantation. Pacemaker and ICD lead parameters before and after LVAD implant were compared. In addition, ventricular tachyarrhythmia event logs and potential electromagnetic interference reports were evaluated.
Results: Right ventricular (RV) sensing decreased in the first 6 months post-LVAD. Mean R-wave amplitude preimplant was 10.9 ± 5.25 mV compared with 7.2 ± 3.4 mV during follow-up (P = 0.02). RV impedance also decreased from 642 ± 240 ohms at baseline to 580 ± 212 ohms at follow-up (P = 0.007). There was a significant increase in RV stimulation threshold following implantation of the LVAD from 0.8 ± 0.6 V at baseline to 1.4 ± 1.0 V in the first 6 months postimplant (P = 0.01). A marked increase in ventricular tachyarrhythmia burden was observed in three patients. One patient displayed electromagnetic interference between the LVAD and defibrillator, resulting in inappropriate defibrillation therapy.
Conclusions: LVADs have a definite impact on cardiac devices in respect with alteration of lead parameters, ventricular tachyarrhythmias, and electromagnetic interference.     

Inappropriate sensing of pectoral myopotentials by an implantable cardioverter defibrillator system

A case of inappropriate detection of pectoral myopotentials by an implantable cardioverter defibrillator (ICD) system due to inadvertent reversal of the high voltage pins in the ICD header is reported. Inappropriate high voltage connections can result in malfunction of both sensing and defibrillation functions of some ICDs.     

Interactions between Pacemakers and Security Systems

Electromagnetic fields arising from a variety of different sources have been shown to interfere with normal pacemaker function. This study evaluated the possible interactions between two modern security systems and different pacemaker types. Fifty–three patients (27 single chamber pacemakers, 25 dual chamber pacemakers) have been tested routinely for their pacemaker function. Thirty–eight patients presented with unipolar sensing and 15 with bipolar sensing. The patients were asked to walk through an installed security system, an antitheft device, and electromagnetic access device with different field strengths while a six–channel ECG monitored the patients. The pacemaker systems were first measured in their basic programmed modes, then the intervention frequency was changed to 100/min and, thereafter, the maximum sensitivity without T wave over– sensing was added. In the security system with the highest field strength (2,700 mA/m), a pacemaker malfunction could be observed in 13% of the monitored patients. In one case, a pacemaker (VVIR) switched to ventricular safety pacing (VOO mode). In the security system with the lower field strength (1,600 mA/m) we found a pacemaker malfunction in 4% of the tested patients. In the antitheft device (50 mA/m). in the electromagnetic access device (300 mA/m), and in pacemaker systems with bipolar sensing, none of these dysfunctions were observed. Phantom programming as described previously did not occur in any of the systems. Persons who are often in the vicinity of security systems should be equipped with a bipolar pacemaker system. Our findings indicate that patients with pacemakers should avoid contact with security systems.     

Incidence and significance of far-field R wave sensing in a VDD-implantable cardioverter defibrillator

BACKGROUND: A VDD-implantable cardioverter-defibrillator (ICD) provides atrioventricular (AV) synchronous stimulation when necessary and incorporates the advantages of dual chamber arrhythmia discrimination algorithms both at potentially lower costs and less periprocedural complications than a DDD-ICD system. A prerequisite for correct dual chamber ICD function is reliable atrial sensing. METHODS: We evaluated atrial near- and ventricular far-field sensing and its impact on the dual-chamber detection algorithm in 106 patients with a single-lead VDD-ICD during a 12-month follow-up period. RESULTS: Six hundred and thirty-nine follow-ups were included. Mean near-field amplitude was 3.82 +/- 1.76 mV; mean far-field amplitude was 0.31 +/- 0.15 mV. 46% of patients had far-fields >0.35 mV and 35% of patients showed atrial EGM markers corresponding to a ventricular far-field in at least one follow-up. Six hundred and forty-five tachycardia episodes were evaluated. Due to far-field sensing, three of 66 episodes (4.5%) of sinus tachycardia were misclassified as ventricular tachycardia (VT), leading to antitachycardia therapies. Delayed detection of VT was seen in a 12 of 323 episodes (3.7%) in five of 62 patients (8%) having VT events (delay 6.4 +/- 6.0 seconds (range 2-24 seconds)). Stable far-field amplitudes <0.2 mV in a follow-up had a high negative predictive value for the occurrence of malfunction during tachycardia-conversely, high far-field amplitudes or a high incidence of far-field markers are only moderately correlated with malfunction. CONCLUSIONS: Ventricular far-field sensing in a VDD-ICD is not uncommon, however, tachycardia detection by the dual chamber algorithm is not seriously impaired by far-field sensing.