Interference with cardiac pacing

In-vivo compatibility between pacemakers and dental equipment

In-vitro studies suggest that electromagnetic interference can occur under specific conditions involving proximity between electronic dental equipment and pacemakers. At present, in-vivo investigations to verify the effect of using electronic dental equipment in clinical conditions on patients with pacemakers are scarce. This study aimed to evaluate, in vivo, the effect of three commonly used electronic dental instruments - ultrasonic dental scaler, electric pulp tester, and electronic apex locator - on patients with different pacemaker brands and configurations. Sixty-six consecutive non-pacemaker-dependent patients were enrolled during regular electrophysiology follow-up visits. Electronic dental tools were operated while the pacemaker was interrogated, and the intracardiac electrogram and electrocardiogram were recorded. No interferences were detected in the intracardiac electrogram of any patient during the tests with dental equipment. No abnormalities in pacemaker pacing and sensing function were observed, and no differences were found with respect to the variables, pacemaker brands, pacemaker configuration, or mode of application of the dental equipment. Electromagnetic interferences affecting the surface electrocardiogram, but not the intracardiac electrogram, were found in 25 (37.9%) patients, especially while using the ultrasonic dental scaler; the intrinsic function of the pacemakers was not affected. Under real clinical conditions, none of the electronic dental instruments tested interfered with pacemaker function.

Perioperative management of cardiac rhythm assist devices in ambulatory surgery and nonoperating room anesthesia

PURPOSE OF REVIEW

Patients with cardiac implantable electronic devices (CIEDs) frequently undergo various surgical procedures and in the past perioperative management involved only placing magnet over the device. New programming features, development of implantable cardiac defibrillator (ICD), cardiac resynchronization therapy, and increasing complexity of the operating room equipment have led to new sources of electromagnetic interference (EMI). A comprehensive understanding of the CIED is necessary to provide a timely and optimal care to the patients.

RECENT FINDINGS

Technological advancements and direct implantation of the transvenous implantable cardiac defibrillators into the heart have led to less clear lines between the pacemakers and the ICD. Subcutaneous ICD as well as the leadless transcatheter deployed intracardiac pacemaker development has complicated the issue further.

SUMMARY

Rapidly developing technologies and increasing number of patients with these devices coming for noncardiac surgeries necessitate continuous education of the anesthesia team regarding perioperative management of such devices.

Safety concerns of Piezoelectric Units in Implantable Cardioverter Defibrillator

PURPOSE

Evidence-based research appears to conflict on the potential risk of electromagnetic interference (EMI) between piezoelectric units (Pzs) and implantable cardioverters and defibrillators (ICDs). The purpose of this study was to observe whether the EMI produced by Pzs is hazardous for ICDs.

MATERIALS AND METHODS

A cross-sectional study of 6 Pzs was conducted in vitro for EMI using an ICD system. To simulate the human body's electrical resistance, electrographic recordings were made of the ICD and lead that were immersed in a bath of saline solution. The variables investigated were the presence of EMI, the distance between the ICD and the Pz, and signal intensity, damage, and type of damage to the ICD and lead. Each series of tests was repeated 3 times, beginning with a 15-second baseline recording (control), until all recording conditions had been covered. Each Pz was recorded under the following conditions: less than 2 cm from the tip of the ICD lead; less than 2 cm from the ICD; less than 2 cm from the lead body and coils; and 15 cm from the lead or the ICD (R4).

RESULTS

In the positive control (direct contact between the lead or the ICD with the Pz switched on), the ICD detected electrical activity as false heart activity. However, after covering all test conditions, no EMI was produced by the Pzs.

CONCLUSION

No EMI or permanent changes in the functioning of the ICD were detected in vitro.

Electromagnetic interference of endodontic equipments with cardiovascular implantable electronic device

OBJECTIVES

Assess the electromagnetic interference (EMI) of endodontic equipment with cardiovascular implantable electronic devices (CIEDs) and related factors.

METHODS

The laser device, electronic apex locators (EAL), optical microscope, endodontic rotary motors, gutta-percha heat carrier (GH), gutta-percha gun and ultrasonic device were tested next to CIEDs (Medtronic and Biotronik) with varied sensitivity settings and distances. CIEDs were immersed in a saline solution to simulate the electrical resistence of the human body. The endodontic equipment was tested in both horizontal and vertical positions in relation to the components of the CIED. The tests were performed on a dental chair in order to assess the cumulative effect of electromagnetic fields.

RESULTS

It was found no EMI with the Biotronik pacemaker. EALs caused EMI with Medtronic PM at a 2 cm distance, with the NSK(®) EAL also affecting the Medtronic defibrillator. GH caused EMI at 2 cm and 5 cm from the Medtronic defibrillator. EMI occurred when devices were horizontally positioned to the CIED. In the majority of the cases, EMI occurred when the pacemaker was set to maximum sensitivity. There was cumulative effect of electromagnetic fields between GH and dental chair.

CONCLUSIONS

EALs and GH caused EMI which ranged according to type and sensitivity setting of the CIEDs and the distance. However, no endodontic equipment caused permanent damage to the CIED. The use of GH caused a cumulative effect of electromagnetic fields. It suggests that during the treatment of patients with CIEDs, only the necessary equipments should be kept turned on.

CLINICAL RELEVANCE

Patients with CIEDs may be subject to EMI from electronic equipment used in dental offices, as they remain turned on throughout the treatment. This is the first article assessing the cumulative effect of electromagnetic fields.

Effects of piezoelectric units on pacemaker function: an in vitro study

INTRODUCTION

The use of piezoelectric units on patients with pacemakers is generally discouraged, although there is no empirical evidence of the effects of current piezoelectric units on pacemaker activity in vitro.

METHODS

Four piezoelectric units (Piezosurgery3, Piezotome, Piezotome2, and Variosurg) and 2 magnetostriction units (Piezotome and Piezotome2) were tested for electromagnetic interference (EMI) with the SENSIA SESR01 pacemaker from Medtronic. The pacemaker, with a single electrode, was immersed in a saline-solution bath and adjusted between 400 and 800 ohms to simulate the electrical resistance of the human body and to register and to produce electrographic recordings. The pacemaker was tested with each ultrasonic device to analyze the presence of EMI at different distances, with the ultrasound switched on, switched off, and during operation. If any of the devices produced interference, the characteristics of the interference were categorized.

RESULTS

In the positive control (direct contact between either the electrode or the generator and the ultrasound device when this was switched on), the pacemaker detected electrical activity as false heart activity. When all the scenarios and distances had been covered, no EMI was produced by the ultrasound units.

CONCLUSIONS

No EMI was detected during the testing of the piezoelectric or magnetostriction units in this in vitro model of pacemaker use.

The effects of six electronic apex locators on pacemaker function: an in vitro study

AIM

To assess the effects of six electronic apex locators (EALs) on pacemaker function in vitro.

METHODOLOGY

Six EALs (Mini Apex Locator®, Dentaport ZX®, Novapex®, Raypex5®, Root ZX mini®, and Justy II®) were tested for electromagnetic interference (EMI) with one pacemaker (Saint Jude Medical). The pacemaker, with a single electrode, was immersed in a saline solution bath adjusted to 400-800 hms to simulate the electrical resistance of the human body and to register the activity by the system. The pacemaker was tested with each of the EALs to analyse the presence of EMI with the EAL switched on, the EAL switched off and during EAL operation. Each series of tests began with a 15-second baseline recording (R0) and continued until all the recording conditions had been covered. The conditions were as follows: R1: recording with the lead of the EAL <2 cm from the tip of the electrode; R2: recording with the lead of the EAL <2 cm from the generator; R3: recording with the lead of the EAL <2 cm from the sensing arc; and R4: recording with the lead of the EAL 15 cm from the sensing arc. If any of the EALs produced interference, its characteristics were categorized.

RESULTS

When the lead of the EAL was <2 cm from the tip of the electrode, the majority of the EALs tested produced only background noise. Only one (the Mini Apex Locator) resulted in EMI that was detected as false heart activity. When the EAL was <2 cm from the generator, just one EAL detected background noise (the Mini Apex Locator). When the EAL was <2 cm from the sensing arc or 15 cm from the sensing arc, the recordings were not affected by any of the EALs. There were no significant differences amongst the EALs analysed with respect to the production of EMI.

CONCLUSIONS

EMI occurred when the EALs were placed close to the tip of the electrode and occasionally when close to the pacemaker; however, no EMI was detected when the EALs were placed near to or 15 cm from the sensing arc in this laboratory experimental model.

A review on remote monitoring technology applied to implantable electronic cardiovascular devices

Implantable electronic cardiovascular devices (IECD) include a broad spectrum of devices that have the ability to maintain rhythm, provide cardiac resynchronization therapy, and/or prevent sudden cardiac death. The incidence of bradyarrhythmias and other cardiac problems led to a broader use of IECD, which turned traditional follow-up into an extremely heavy burden for healthcare systems to support. Our aim was to assess the impact of remote monitoring on the follow-up of patients with IECD. We performed a review through PubMed using a specific query. The paper selection process included a three-step approach in which title, abstract, and cross-references were analyzed. Studies were then selected using previously defined inclusion criteria and analyzed according to the country of origin of the study, year, and journal of publication; type of study; and main issues covered. Twenty articles were included in this review. Eighty percent of the selected papers addressed clinical issues, from which 94% referred clinical events identification, clinical stability, time savings, or physician satisfaction as advantages, whereas 38% referred disadvantages that included both legal and technical issues. Forty-five percent of the papers referred patient issues, from which 89% presented advantages, focusing on patient acceptance/satisfaction, and patient time-savings. The main downsides were technical issues but patient privacy was also addressed. All the papers dealing with economic issues (20%) referred both advantages and disadvantages equally. Remote monitoring is presently a safe technology, widely accepted by patients and physicians, for its convenience, reassurance, and diagnostic potential. This review summarizes the principles of remote IECD monitoring presenting the current state-of-the-art. Patient safety and device interaction, applicability of current technology, and limitations of remote IECD monitoring are also addressed. The use of remote monitor should consider the selection of patients, the type of disease, and centers' availability to receive, interpret and respond to device alerts. Before remote IECD monitoring can be routinely used, technical, procedure, and ethical/legal issues should be addressed.

A model for determining the induced voltage at the terminals of a pacemaker exposed to a low frequency magnetic field

This paper presents a method for calculating induced voltage, in vitro, at the terminals of a unipolar pacemaker (PM) subjected to a low frequency magnetic field. We propose a theoretical model which has been experimentally verified by using a homogeneous phantom model placed at the centre of the source generating a homogeneous magnetic field. The levels of the magnetic field used in our experiment are in accordance with the European Directive 2004/40/EC, which sets the occupational electromagnetic field exposure limits. The voltage induced at the terminals of an implanted pacemaker results in the superimposition of two different voltage sources. The first is due to the presence of the loop formed by the PM system and the second is due to the induced currents circulating in the coupling medium. The influence of the induced currents, calculated by the impedance method, is weak compared to the voltage of the loop. The theoretical results obtained agree with the experimental value. Thus, the proposed model can be used to predict the behaviour of a pacemaker subjected to a low frequency magnetic field as well as to those fields within the accepted exposure limits for a patient with a pacemaker.

Clinical safety of magnetic resonanceimaging early after coronary artery stent placement

OBJECTIVES

Our aim was to examine the rate of adverse cardiac events in patients undergoing magnetic resonance imaging (MRI) <8 weeks after coronary stent placement.

BACKGROUND

The risk of coronary stent thrombosis from dislodgement due to MRI early after stent placement is not well defined. Manufacturers recommend postponing MRI studies until eight weeks after coronary stent placement.

METHODS

We analyzed the Mayo Clinic Rochester Percutaneous Coronary Intervention Database and examined records of 111 patients who underwent MRI <8 weeks after coronary stent placement treated with aspirin and a thienopyridine. Occurrence of death, myocardial infarction (MI), and repeat revascularization within 30 days of MRI were recorded.

RESULTS

Magnetic resonance imaging (1.5 tesla) was performed within a median of 18 days (range, 0 to 54 days) after coronary stent placement. Four noncardiac deaths occurred, and three patients had repeat revascularization procedures. Stent thrombosis did not occur (95% confidence interval, 0% to 3.3%).

CONCLUSIONS

Magnetic resonance imaging <8 weeks after coronary stent placement appears to be safe, and the risk of cardiac death or MI due to stent thrombosis is low. Postponing MRI does not appear to be necessary.

Electronic medical devices: a primer for pathologists

CONTEXT

Electronic medical devices (EMDs) with downloadable memories, such as implantable cardiac pacemakers, defibrillators, drug pumps, insulin pumps, and glucose monitors, are now an integral part of routine medical practice in the United States, and functional organ replacements, such as the artificial heart, pancreas, and retina, will most likely become commonplace in the near future. Often, EMDs end up in the hands of the pathologist as a surgical specimen or at autopsy. No established guidelines for systematic examination and reporting or comprehensive reviews of EMDs currently exist for the pathologist.

OBJECTIVE

To provide pathologists with a general overview of EMDs, including a brief history; epidemiology; essential technical aspects, indications, contraindications, and complications of selected devices; potential applications in pathology; relevant government regulations; and suggested examination and reporting guidelines.

DATA SOURCES

Articles indexed on PubMed of the National Library of Medicine, various medical and history of medicine textbooks, US Food and Drug Administration publications and product information, and specifications provided by device manufacturers.

STUDY SELECTION

Studies were selected on the basis of relevance to the study objectives.

DATA EXTRACTION

Descriptive data were selected by the author.

DATA SYNTHESIS

Suggested examination and reporting guidelines for EMDs received as surgical specimens and retrieved at autopsy.

CONCLUSIONS

Electronic medical devices received as surgical specimens and retrieved at autopsy are increasing in number and level of sophistication. They should be systematically examined and reported, should have electronic memories downloaded when indicated, will help pathologists answer more questions with greater certainty, and should become an integral part of the formal knowledge base, research focus, training, and practice of pathology.

Preoperative assessment and perioperative management of the patient with nonischemic heart disease

We have reviewed important issues relating to hypertension, congestive heart failure, arrhythmias and conduction defects, and valvular heart disease in caring for the patient with nonischemic heart disease in the perioperative period. Careful assessment by history and physical examination along with targeted testing will allow the clinician to identify potential complications, provide guided medical therapy, and better utilize other resources to reduce perioperative risk.

Effect of electronic apex locators on cardiac pacemaker function

The purpose of this study was to assess the effects of five electronic apex locators on pacemaker function in vitro. A Biotronik Actros DR+ pacemaker was evaluated at maximum sensitivity on a flat bench top. The pacemaker lead, electronic apex locator, and oscilloscope were connected across a 150-ohm resistor. Pace monitoring was carried out with a Biotronik EPR 1000 programmer and a Tektronix TDS 220 2-channel digital real-time oscilloscope. Four of five electronic apex locators tested did not cause inhibition or interfere with normal pacemaker function. It seems that electronic apex locators can be used safely in patients with pacemakers.

Emergencies related to implantable cardioverter-defibrillators

Implantable cardioverter-defibrillators (ICDs) have become the dominant therapeutic modality for patients with life-threatening ventricular arrhythmias. ICDs are implanted using techniques similar to standard pacemaker implantation. They not only provide high-energy shocks for ventricular fibrillation and rapid ventricular tachycardia, but also provide antitachycardia pacing for monomorphic ventricular tachycardia and antibradycardia pacing. Devices incorporating an atrial lead allow dual-chamber pacing and better discrimination between ventricular and supraventricular tachyarrhythmias. Intensivists are increasingly likely to encounter patients with ICDs. Electrosurgery can be safely performed in ICD patients as long as the device is deactivated before the procedure and reactivated and reassessed immediately afterward. Prompt and skilled intervention can prove to be life-saving in patients presenting with ICD-related emergencies, including lack of response to ventricular tachyarrhythmias, pacing failure, and multiple shocks. Recognition and treatment of tachyarrhythmia can be temporarily disabled by placing a magnet on top of an ICD. The presence of an ICD should not deter standard resuscitation techniques. Multiple ICD discharges in a short period of time constitute a serious situation. Causes include ventricular electrical storm, inefficient defibrillation, nonsustained ventricular tachycardia, and inappropriate shocks caused by supraventricular tachyarrhythmias or oversensing of signals. ICD system infection requires hardware removal and intravenous antibiotic therapy. Deactivation of an ICD with the consent of the patient or relatives is reasonable and ethical in terminally ill patients.