The response of implanted dual chamber pacemakers to 50 Hz extraneous electrical interference

Prepare for Take-Off: Fasten Your Seatbelt and Keep a Magnet in Your Pocket!

Fainting on a plane is quite common, and stewards are used to taking care of things. Statistically, there is always a physician on board. This Letter to the Editor details a case report that deals with inappropriate pacemaker inhibition during a flight.

RocheNC, ThabouillotO, BouvierF, PauleP. Prepare for take-off: fasten your seatbelt and keep a magnet in your pocket!. Prehosp Disaster Med. 2018;33(1):114–115.

Inappropriate implantable cardioverter-defibrillator shocks attributed to alternating-current leak in a swimming pool

Implantable cardioverter-defibrillators (ICDs) are the standard of care for preventing sudden cardiac death in patients who are predisposed to malignant ventricular arrhythmias. Causes of inappropriate ICD shock include equipment malfunction, improper arrhythmia evaluation, misinterpretation of myopotentials, and electromagnetic interference. As the number of implanted ICDs has increased, other contributors to inappropriate therapy have become known, such as minimal electrical current leaks that mimic ventricular fibrillation. We present the case of a 63-year-old man with a biventricular ICD who received 2 inappropriate shocks, probably attributable to alternating-current leaks in a swimming pool. In addition, we discuss ICD sensitivity and offer recommendations to avoid similar occurrences.

Unipolar cardiac pacemakers in electromagnetic fields of high voltage overhead lines

Experimental studies have shown that both electric and magnetic extremely low frequency fields are able to disturb a cardiac pacemaker (CPM) at certain field strengths. However, the simultaneous influence of multiphase electric and magnetic fields beneath high voltage overhead lines (HVOLs) has not yet been investigated. Therefore, the distribution of the electric and the magnetic field as well as the phase angle between both components for an exemplary HVOL was numerically calculated. The calculations show that the phase difference of the capacitive and the inductive induced voltage on the input of an implanted cardiac pacemaker is position-dependent. Based on these and our earlier results a worst-case-scenario for two virtual patients beneath an exemplary HVOL was derived. It turned out that although the interference of CPMs by the electromagnetic fields (EMFs) of HVOLs cannot be ruled out, the life-threatening interference condition 'inhibition by EMF' is unlikely. Due to various factors depending on technical parameters and the individual patient a definite answer about the disturbance of an implanted CPM beneath HVOLs can be given by studies with real CPM patients only.

Influence des champs électromagnétiques non ionisants sur les dispositifs cardiaques médicaux implantables

AN INCREASINGLY FREQUENT PROBLEM: Since sources of electromagnetic interferences can alter the functioning of pacemakers (PM) and implantable cardioverter-defibrillators (ACD) are increasing and cover wide range of frequencies, from 0 to 300 GHz, including very low (VLF) and radio-frequencies (RF), carriers of such devices can suffer from decreased quality of life, without clinical impact, or even dangerous situations. PACEMAKERS: Pacemakers and implantable cardioverter-defibrillators are usually well protected from external interference. With pacemakers, such problems are handled fairly well and the consequences are usually benign. REGARDING DEFIBRILLATION: An interference can result in the inappropriate functioning of the device, the first consequence of which is an unexpected shock for the patient or, conversely, the lack of effective treatment when the patient most needs it. With ICD, the data in the literature suggest more attention should be paid, notably with anti-theft detector gates.

Mohs Micrographic Surgery in a Patient with a Deep Brain Stimulator: A Review of the Literature on Implantable Electrical Devices

BACKGROUND

Implantable electrical devices are becoming increasingly common in the patient population presenting for Mohs micrographic surgery. In addition to understanding the potential intraoperative complications with implantable cardioverter-defibrillators and pacemakers, the Mohs surgeon needs to be aware of the relatively new treatment of movement disorders using implanted deep brain stimulators.

OBJECTIVE

We present only the second reported case of Mohs surgery in a patient with a deep brain stimulator. In an attempt to help minimize adverse events during a procedure, we review the more commonly encountered electrical devices as well as the newer deep brain stimulators. We provide guidelines for the avoidance of electromagnetic interference during an electrosurgical procedure.

METHODS

This 76-year-old patient with Parkinson's disease and an implanted deep brain stimulator underwent Mohs surgery for excision of a squamous cell carcinoma on the ear. In an attempt to minimize electromagnetic interference with his implanted device, hemostasis was obtained with the aid of a battery-operated heat-generating handheld electrocautery device.

RESULTS

The patient tolerated the procedure well without complications or reports of discomfort.

CONCLUSION

Patients with implanted electrical devices are subject to electromagnetic interference during an electrosurgical procedure. Care must be taken in this expanding patient population during a Mohs surgical procedure.

Noise reversion in paced dogs

Pacemakers are commonly implanted by veterinary cardiologists in dogs with bradyarrhythmias. In the past, these pacemakers were placed with little attention to programming except for the basic heart rate. However, the availability of pacing programmers has permitted a better appreciation of the needs for proper and safe pacing in dogs. An awareness of the problems that can result from improper programming is imperative. We report the identification of noise reversion (inappropriate asynchronous pacing) in 42% of dogs consecutively paced (n = 19) at Cornell University during a 2 year period. Noise reversion is the operation that causes the pacemaker to switch to asynchronous pacing with repetitive refractory sensing. It was developed as a protective mechanism against noise being mistaken for cardiac events with the consequence of inhibition of pacing. However, in the dog, this operation can cause inappropriate, and potentially dangerous pacing. In the dog, this common complication is associated with the coexistence of a bradycardia and tachycardia. Proper programming of the refractory period (shortening) in conjunction with the sensitivity (decreasing the sensitivity) can eliminate noise reversion in dogs with both ventricular and atrial pacing.

Pacemaker interference by 60-Hz contact currents

Contact currents occur when a person touches conductive surfaces at different potentials, thereby completing a path for current flow through the body. Such currents provide an additional coupling mechanism between the human body and external low-frequency fields. The resulting fields induced in the body can cause interference with implanted cardiac pacemakers. Modern computing resources used in conjunction with millimeter-scale human body conductivity models make numerical modeling a viable technique for examining any such interference. An existing well-verified scalar-potential finite-difference frequency-domain code has recently been modified to allow for combined current and voltage electrode sources, as well as to allow for implanted wires. Here, this code is used to evaluate the potential for cardiac pacemaker interference by contact currents in a variety of configurations. These include current injection into either hand, and extraction via: 1) the opposite hand; 2) the soles of both feet; or 3) the opposite hand and both feet. Pacemaker generator placement in both the left and right pectoral areas is considered in conjunction with atrial and ventricular electrodes. In addition, the effects of realistically implanted unipolar pacemaker leads with typical lumped resistance values of either 20 kohms and 100 kohms are investigated. It is found that the 60-Hz contact current interference thresholds for typical sensitivity settings of unipolar cardiac pacemaker range from 24 to 45 microA. Voltage and electric field dosimetry are also used to provide crude threshold estimates for bipolar pacemaker interference. The estimated contact current thresholds range from 63 to 340 microA for bipolar pacemakers.

Pacemaker interference by magnetic fields at power line frequencies

Human exposure to external 50/60-Hz electric and magnetic fields induces electric fields within the body. These induced fields can cause interference with implanted pacemakers. In the case of exposure to magnetic fields, the pacemaker leads are subject to induced electromotive forces, with current return paths being provided by the conducting body tissues. Modern computing resources used in conjunction with millimeter-scale human body conductivity models make numerical modeling a viable technique for examining any such interference. In this paper, an existing well-verified scalar-potential finite-difference frequency-domain code is modified to handle thin conducting wires embedded in the body. The effects of each wire can be included numerically by a simple modification to the existing code. Results are computed for two pacemaker lead insertion paths, terminating at either atrial or ventricular electrodes in the heart. Computations are performed for three orthogonal 60-Hz magnetic field orientations. Comparison with simplified estimates from Faraday's law applied directly to extracorporeal loops representing unipolar leads underscores problems associated with this simplified approach. Numerically estimated electromagnetic interference (EMI) levels under the worst case scenarios are about 40 microT for atrial electrodes, and 140 microT for ventricular electrodes. These methods could also be applied to studying EMI with other implanted devices such as cardiac defibrillators.

Cardiac pacing. A review

Pacing is a field of rapid clinical progress and technologic advances. Clinical progress in the 1990s included the refinement of indications for pacing as well as the use of pacemakers for new, nonbradycardiac indications, such as the treatment of cardiomyopathies and CHF and the prevention of atrial fibrillation. Important published data and studies in progress are shedding new light on issues of pacing mode selection, and they may influence future practice significantly. Important technologic advances include development of new rate-adaptive sensors and sensor combinations and the evolution of pacemakers into sophisticated diagnostic devices with the capability to store data and ECGs. Automatic algorithms monitor the patient for appropriate capture, sensing, battery status, and lead impedance, providing better patient safety and pacemaker longevity.

Pacemaker interference and low-frequency electric induction in humans by external fields and electrodes

The possibility of interference by low-frequency external electric fields with cardiac pacemakers is a matter of practical concern. For pragmatic reasons, experimental investigations into such interference have used contact electrode current sources. However, the applicability to the external electric field problem remains unclear. The recent development of anatomically based electromagnetic models of the human body, together with progress in computational electromagnetics, enable the use of numerical modeling to quantify the relationship between external field and contact electrode excitation. This paper presents a comparison between the computed fields induced in a 3.6-mm-resolution conductivity model of the human body by an external electric field and by several electrode source configurations involving the feet and either the head or shoulders. The application to cardiac pacemaker interference is also indicated.

Interference with cardiac pacing

Most exposures to electromagnetic interference are transient and pose no threat to patients with pacemakers and implantable cardioverter defibrillators. Prolonged exposure may be catastrophic in pacemaker dependent patients. New technologies (wireless phones, electronic antitheft surveillance) are safe if proper precautions are takes. Radiofrequency ablation requires concomitant temporary pacing. MR imaging remains contraindicated in patients with these devices until further study is undertaken.

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 oversensing 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.

Dermatologic electrosurgery in patients with implantable cardioverter-defibrillators and pacemakers

BACKGROUND

Electrosurgery is frequently employed in the treatment of skin cancer and other dermatologic conditions in the elderly. Implantable cardioverter-defibrillators (ICDs) and pacemakers are most commonly seen in this older population. Potentially hazardous electrosurgical interference exists with the function of ICDs and pacemakers in this setting.

OBJECTIVE

Our goal is to review the potential hazards of electrosurgery in patients with ICDs and pacemakers and to suggest a perioperative management plan.

METHODS

Review of the medical literature on electrosurgical interference with ICDs and pacemakers was accomplished in addition to a case report of ventricular tachycardia during Mohs surgery on a patient with an ICD.

RESULTS

Multiple case reports and reviews from the nonder-matologic literature demonstrate that a real hazard exists.

CONCLUSION

Knowledge of the potential electrosurgical interference with ICDs and pacemakers is required to perform these procedures safely. A perioperative management plan is suggested.

State of the science: pacemaker and defibrillator interference from wireless communication devices

The use of wireless communication devices has increased rapidly, with current industry estimates of 50,000,000 subscribers of cellular telephone services, a number that is expected to double by the year 2000. Because wireless communication devices emit RF signals, they have the potential to interfere with implantable devices. The mechanism of interference and the magnitude of interference must be considered in terms of the type of wireless communication device being used and the characteristics of the individual implantable device that is exposed to the RF emission of the cellular phone. This article reviews the potential effects of wireless communication devices on implantable devices and makes initial recommendations for patients with implantable devices.