Unipolar Pacemaker Research Articles

Device-device interaction

With a continuous increase in the approval of cardiac implantable electronic devices (CIED), not only pacemakers (PM) and implantable cardioverter defibrillators (ICD) but especially devices for treating chronic heart failure, more and more possibilities of device-device interactions arise, which in isolated cases can lead to death of the patient. Because of the still low numbers of patients overall, there are very few scientific studies and only isolated case reports on this topic. Devices which are at risk of interaction with a previously implanted PM are wearable cardioverter defibrillators (WCD) and subcutaneous ICDs (S-ICD). These two devices both use the surface electrocardiogram (ECG) in their algorithm for detecting ventricular arrhythmia. These surface ECGs seem to be prone to unipolar pacemaker stimulation artefacts. By correct programming of implanted pacemakers in the bipolar stimulation mode it is possible to avoid ECG artefacts and inadequate treatment. In baroreceptor activation therapy (BAT) there seem to be no device interactions so far, even though this device shows substantial highly frequent artefacts in the ECG. The cardiac contractility modulation (CCM) system has also until now not shown interactions with transvenous or subcutaneous ICD devices, even though randomized trials are missing.

Safety and interaction of patients with implantable cardiac defibrillators driving a hybrid vehicle

BackgroundElectromagnetic interference (EMI) can affect the function of implantable cardioverter defibrillators (ICD). Hybrid electric vehicles (HEV) have increased popularity and are a potential source of EMI. Little is known about the in vivo effects of EMI generated by HEV on ICD. ObjectiveThis study evaluated the in vivo interaction between EMI generated by HEV with ICD. Methods and resultsThirty patients (73±9 y/o; 80% male) with stable ICD function were exposed to EMI generated by a Toyota Prius Hybrid®. The vehicle was lifted above the ground, allowing safe changes in engine rotation and consequent variations in electromagnetic emission. EMI was measured (NARDA STS® model EHP-50C) and expressed in A/m (magnetic), Volts/m (electrical), and Hertz (frequency). Six positions were evaluated: driver, front passenger, right and left back seats, outside, at the back and front of the car. Each position was evaluated at idle, 30 mph, 60 mph and variable speeds (acceleration-deceleration-brake). All ICD devices were continuously monitored during the study.The levels of EMI generated were low (highest mean levels: 2.09A/m at right back seat at 30 mph; and 3.5V/m at driver seat at variable speeds). No episode of oversensing or inadvertent change in ICD programming was observed. ConclusionIt is safe for patients with ICD to interact with HEV. This is the first study to address this issue using an in vivo model. Further studies are necessary to evaluate the interaction of different models of HEV or electric engine with ICD or unipolar pacemakers.

96-53: Transvenous unipolar pacemaker lead extraction - differences with other leads. Experience among 2022 TLE procedures

96-53: Transvenous unipolar pacemaker lead extraction - differences with other leads. Experience among 2022 TLE procedures

Syncope as a presenting feature of complete extrusion of a unipolar permanent pacemaker

Complete extrusion of a permanent pacemaker is an extremely rare complication. We report a unique case of a patient presenting with syncopal episodes after complete extrusion of his implanted pacemaker. An 82-year-old gentleman with a history of pacemaker implantation, 6 years back, presented with syncopal episodes and was found to have complete extrusion of his pacemaker out of its pocket. An electrocardiography revealed complete heart block which would revert to paced rhythm when the pulse generator would be pushed back into the pacemaker pocket. Neglecting the pre-extrusion stage, he presented with syncopal episodes after complete extrusion and loss of contact of the unipolar pacemaker with the pacemaker pocket resulting in complete loss of pacing.

A low-cost device for contactless detection of pacemaker pulses

A new sensor capable to detect pacemaker pulses without using electrodes is presented. The magnetic field associated to the pacing current is sensed by a coil placed in proximity of the pacemaker wire, without the need of any electric connection with the patient. The new sensor is capable to provide accurate measurement of the occurrence and timing of pacemaker pulses. Hence, it provides important information about the pacemaker functioning, which can be used in patient’s monitoring and pacemaker device assessment. An in-vitro testing of the new sensor was carried out involving a real unipolar pacemaker immersed in saline solution. A wideband ECG circuit was also realized to record pacemaker pulses. The electrocardiographic signal and the output of the sensor were simultaneously recorded and compared. A microcontroller-based circuit provides accurate timing measurements of inter-pulse intervals and pulse duration and display them in real-time. Preliminary results suggest the possibility to use the new sensor to achieve prolonged, passive, unobstructive and wearable monitoring of pacemaker patients during their daily life activities. Accurate timing of the pacemaker pulse can also support standard ECG diagnosis and measurement of the residual charge of the pacemaker battery.

Does Bipolar Pacemaker Current Activate Blood Platelets?

The aim of this study was to investigate whether bipolar pacemaker current lead can activate blood platelets. The null hypothesis was that 1 minute of electrical stimulation of platelets would not influence their subsequent reactivity to adenosine diphosphate (ADP). Both platelets and muscle cells contain actin and myosin filaments, and both cells are activated following calcium influx. Muscle cells open their calcium channels and contract when exposed to an electric current. Current through a bipolar pacemaker lead will expose a small volume of blood, including platelets, to the depolarizing current. Platelet activation may ensue, resulting in aggregation, release reaction, and contraction. In contrast, a unipolar pacemaker system will not depolarize blood, but transmit current directly into the myocardium, and the current afterward passes through other tissues before returning to the pacemaker can. Platelet-rich plasma was prepared from two healthy subjects. Platelet reactivity to the agonist ADP was tested in paired samples in an aggregometer in a case/control setup. Eighteen of 46 tested pairs of platelet-rich plasma showed increased reactivity in the paced sample; 26 were unchanged while two showed decreased reactivity in the paced sample. Using a two-sided sign test, the null hypothesis was rejected (P = 0.0004). The study demonstrates increased reactivity to ADP in platelets exposed in vitro to stimulation by pacemaker current. The clinical relevance of these findings remains to be investigated.

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.

A Fatal Device‐Device Interaction between a Wearable Automated Defibrillator and a Unipolar Ventricular Pacemaker

We report a fatal device-device interaction between a wearable automated defibrillator (WAD; LifeVest - LifeCor, Inc., Pittsburgh, PA, USA) and a unipolar pacemaker that occurred in an 18-year-old patient listed for cardiac transplantation due to his failing Fontan. The patient developed ventricular tachycardia that was initially detected by the WAD. However, large unipolar pacing artifacts and specific WAD arrhythmia detection algorithms caused the WAD to revert to nonrecognition of the arrhythmia, which lead to the patient's death. We identify likely causes of the failure and suggest methods of preventing such occurrences in the future.

Do induction cooktops interfere with cardiac pacemakers?

In induction cooktops, coils produce time-varying magnetic fields that induce eddy currents in the ferromagnetic bottom of a pot or pan, thereby heating it, while the cooktop itself remains cool. Interference with pacemaker sensing could conceivably be produced by voltages induced directly by induction or indirectly by leakage currents. A worst-case pacemaker-patient (PP) model representing left-sided implantation of a unipolar pacemaker was used for measurement of induced voltages, to judge whether induction cooktops could interfere with pacemaker sensing. Eleven induction cooktops of European manufacture were tested using the PP model. The pacemaker sensitivity with respect to 24 kHz voltages, amplitude-modulated at 100 Hz, was investigated in 244 devices. The current passing through the body of a grounded patient touching a metal pot was determined by measuring the voltage from hand to hand and between electrodes placed on the thorax to simulate an implanted unipolar pacing system underneath. The results obtained were complex. If the pot is positioned concentrically with the induction coil, the smallest pot produced the largest stray field, but the induced voltage always remained below the critical value of 100 mV. With eccentrically positioned large pots, voltages of up to 800 mV could be induced. The induced voltage could always be reduced to </=60 mV by maintaining a distance of 35 cm. The most sensitive pacemaker reacted at 90.5 mV. Because of leakage current, approximately 2% of the voltage between pot and ground appears across the pacemaker's sensing input. Patients are at risk if the implant is unipolar and left-sided, if they stand as close as possible to the induction cooktop, and if the pot is not concentric with the induction coil. Unipolar pacing systems can sense interference generated by leakage currents if the patient touches the pot for a long period of time. The most likely response to interference is switching to an asynchronous interference mode. Patients with unipolar pacemakers are at risk only if they are not pacemaker-dependent.

Numerical modeling of pacemaker interference in the electric-utility environment

Potential for electromagnetic interference (EMI) with cardiac pacemakers in workplaces in electric utilities due to 50- and 60-Hz fields is well known. Only younger employees of electric-utility companies may want to return to their jobs that often entail exposure to such fields. EMI may occur due to exposure to strong external electric fields, magnetic fields, contact currents, and electrostatic discharges (ESD). Numerical modeling of the potential differences produced between the pacemaker electrodes in situ, i.e., in the heterogeneous model of a human body, allows for the evaluation of potential EMI prior to an implantation of the device. Such modeling has been performed and the results are presented and compared for different conditions of potential EMI. As expected, unipolar pacemakers are more susceptible than bipolar devices.

Do induction cooktops interfere with cardiac pacemakers?

Aims In induction cooktops, coils produce time-varying magnetic fields that induce eddy currents in the ferromagnetic bottom of a pot or pan, thereby heating it, while the cooktop itself remains cool. Interference with pacemaker sensing could conceivably be produced by voltages induced directly by induction or indirectly by leakage currents. Methods and results A worst-case pacemaker-patient (PP) model representing left-sided implantation of a unipolar pacemaker was used for measurement of induced voltages, to judge whether induction cooktops could interfere with pacemaker sensing. Eleven induction cooktops of European manufacture were tested using the PP model. The pacemaker sensitivity with respect to 24 kHz voltages, amplitude-modulated at 100 Hz, was investigated in 244 devices. The current passing through the body of a grounded patient touching a metal pot was determined by measuring the voltage from hand to hand and between electrodes placed on the thorax to simulate an implanted unipolar pacing system underneath. The results obtained were complex. If the pot is positioned concentrically with the induction coil, the smallest pot produced the largest stray field, but the induced voltage always remained below the critical value of 100 mV. With eccentrically positioned large pots, voltages of up to 800 mV could be induced. The induced voltage could always be reduced to ≤60 mV by maintaining a distance of 35 cm. The most sensitive pacemaker reacted at 90.5 mV. Because of leakage current, ∼2% of the voltage between pot and ground appears across the pacemaker's sensing input. Conclusion Patients are at risk if the implant is unipolar and left-sided, if they stand as close as possible to the induction cooktop, and if the pot is not concentric with the induction coil. Unipolar pacing systems can sense interference generated by leakage currents if the patient touches the pot for a long period of time. The most likely response to interference is switching to an asynchronous interference mode. Patients with unipolar pacemakers are at risk only if they are not pacemaker-dependent.

Cross-talk inhibition and asystole resulting from postshock high-output pacing: A new form of implantable cardioverter-defibrillator proarrhythmia

c p Cross-talk inhibition, the oversensing of an atrial pacing ulse in the ventricular channel, has been described primarly in patients with unipolar pacemakers and high atrial utputs. Although their high operating ventricular sensitivty could make implantable cardioverter-defibrillators ICDs) prone to cross-talk inhibition, this complication has een very uncommon. Extended cross-chamber blanking eriods and “safety pacing” or similar algorithms are proective. In this report, we describe an unforeseen complicaion of high-output postshock atrial pacing in a patient with n ICD and underlying complete heart block: near-fatal ross-talk inhibition resulting in prolonged asystole.

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.

Induction ovens and electromagnetic interference: what is the risk for patients with implanted pacemakers?

Electromagnetic fields may interfere with normal pacemaker function. Despite the introduction of modern pacemakers and bipolar lead systems, electromagnetic interference (EMI) still remains to be a concern during daily lives when patients are exposed to cellular phones, electronic security systems, and several household appliances. The aim of this study was to evaluate potential EMI risk of induction ovens, which are increasingly used in private households. The study included 40 consecutive patients (22 men, 18 women; age 73 +/- 11 years) with implanted DDD, VVI, VDD, and AAI pacemaker systems. The pacemakers were programmed to unipolar sensing and pacing. Sensitivity remained unchanged, if the measured sensing threshold was more than twice the programmed value; otherwise, it was set at half of the measured sensing threshold. Patients were placed in a sitting position at the closest possible distance of about 20 cm between two cooking pots and pacemaker bending the upper part of the body slightly over the induction oven. The energy was increased stepwise to the maximum. One pot was removed and placed again at the highest oven level. Potential interference was monitored continuously. The study showed no incidence of pacemaker malfunction during the entire test while the patients with intrinsic cardiac rhythms were exposed to the induction oven at varying energy strengths. Likewise, there was no external interference when the patients were paced at heart rates of 10-15 beats/min above their heart rates. The programmed parameters remained unchanged after the study. In conclusion, this study shows no EMI risk of an induction oven in patients with bipolar or right-sided unipolar pacemakers.

Electronic security systems and active implantable medical devices.

How do active implantable medical devices react in the presence of strong magnetic fields in the frequency range between extremely low frequency (ELF) to radiofrequency (RF) as they are emitted by electronic security systems (ESS)? There are three different sorts of ESSs: electronic article surveillance (EAS) devices, metal detector (MDS) devices, and radiofrequency identification (RFID) systems. Common to all is the production of magnetic fields. There is an abundance of literature concerning interference by ESS gates with respect to if there is an influence possible and if such an influence can bear a risk for the AIMD wearers. However, there has been no attempt to study the physical mechanism nor to develop a model of how and under which conditions magnetic fields can influence pacemakers and defibrillators and how they could be disarmed by technological means. It is too often assumed that interference of AIMD with ESS is inevitable. Exogenous signals of similar intensity and rhythm to heart signals can be misinterpreted and, thus, confuse the implant. Important for the interference coupling mechanism is the differentiation between a "unipolar" and a "bipolar" system. With respect to magnetic fields, the left side implanted pacemaker is the most unfavorable case as the lead forms approximately a semicircular area of maximum 225 cm2 into which a voltage can be induced. This assumption yields an interference coupling model that can be expressed by simple mathematics. The worst-case conditions for induced interference voltages are a coupling area of 225 cm2 that is representative for a large human, a homogeneous magnetic field perpendicular to the area formed by the lead, and a unipolar ventricular pacemaker system that is implanted on the left side of the thorax and has the highest interference sensitivity. In bipolar systems the fields must be 17 times larger when compared to a unipolar system to have the same effect. The magnetic field for interfering with ICDs must be 1.7 stronger than that of the most sensitive unipolar pacemaker. The lowest interference thresholds measured over the last 10 years in the low frequency range (16 2/3 Hz-24 kHz) together with thresholds > 24 kHz that were supplied by the CETECOM study are listed. Both sets of data together with the coupling model, allow for judging which fields of ESSs could influence AIMDs. From measurements at gate antennas, it is possible to derive a "maximum allowed field" curve over the whole frequency range, below which no interference will occur. Comparison of data from literature with these maximum allowed fields confirm the correctness of the calculations. Thus, it is possible to predict interference situations in gates if the magnetic field is known. If all future pacemakers were to have the immunity against interference of the better 50% of today's pacemakers, the magnetic field ceiling values could be at least four times higher. The same is true if the ventricular sensitivity is routinely set at 7 mV. Pacemaker manufacturers should consider filter improvement with modern technology, but gate manufacturers should not claim the privilege of being out of bounds.

Safety of a permanent unipolar rate adaptive pacemaker during prolonged helicopter travel

Safety of a permanent unipolar rate adaptive pacemaker during prolonged helicopter travel

The interference threshold of unipolar cardiac pacemakers in extremely low frequency magnetic fields

The effective induction loop area of implanted cardiac pacemaker (CPM) systems in magnetic fields was determined. The results were verified in a tank model placed in the centre of a Helmholtz-coil-arrangement. Both a left and a right pectorally implanted unipolar dual chamber CPM system were simulated. On this basis and with the results of benchmark-tests the interference thresholds for a collection of modern CPMs in extremely low frequency (ELF) magnetic fields were estimated. The investigations clearly showed that there are two loops, the CPM-lead-tissue-loop and the body loop, responsible for the magnitude of the disturbance voltage on the input of a cardiac pacemaker. The effective induction loop areas ranged from 100 to 221 cm2. For a left pectorally implanted, atrially controlled CPM system the interference thresholds for the magnetic induction lay between 16 and 552 µ T (RMS) for frequencies of the magnetic field between 10 and 250 Hz. Thus, there is a limited possibility for an interference of implanted CPMs by ELF magnetic fields in everyday life.

Multiple adverse events with a dual chamber pacemaker.

The aim of the study was to evaluate our experience with Physiocor 400T, a dual chamber unipolar pacemaker manufactured by Sorin Biomedica. Between March 1993 and December 1994, 63 units of that model were implanted at our center. Patients were followed for 46 +/- 16 months. By the end of follow-up, 15 patients had died, 1 patient was lost to follow-up, and two units had been replaced for unrelated reasons. During follow-up the following phenomena had been observed: (1) Spontaneous backup reversion (VOO, 80 ppm) in 6 (9.5%) of 63 patients. In three patients this phenomenon was accompanied by concomitant ineffective pacing artifacts at 130 beats/min with very low pulse widths. (2) Unexpected battery depletion (EOL) occurred in 3 (5%) of 63 patients; two of the three occurred within weeks of routine evaluation that confirmed normal battery status. (3) Early elective replacement time (ERT) unpreceded by a gradual drop in magnet rate in 2 (3.2%) of 63 patients. (4) Total loss of telemetry without change in pacing mode in 1 (1.6%) of 63 patients. The estimated event-free 5-year survival of this model was 46%. In conclusion, 12 (19%) of 63 patients had adverse events with Physiocor 400T pacemakers. The potential risk of asynchronous pacing for prolonged periods and the risk of unexpected EOL warrants consideration of elective replacement of all remaining units.

Spinal Cord Stimulation for Intractable Angina Pectoris

Spinal Cord Stimulation for Intractable Angina Pectoris

The Combined Transvenous Implantation of Cardioverter Defibrillators and Permanent Pacemakers

We developed criteria for implantation and programming of permanent endocardial pacemakers in patients with a nonthoracotomy ICD system. These criteria were prospectively used in 10 patients who recieved an ICD prior to (n = 5) or following (n = 5) implantation of a dual chamber (n = 6) or ventricular (n = 4) pacemaker with a unipolar (n = 4) or bipolar (n = 6) lead configuration. All patients were tested for interactions or malfunctions. Undersensing of ventricular fibrillation by the atrial sense amplifier and inadequate atrial pacing occurred in one patient with a unipolar dual chamber system programmed to AAIR but didn't impair ICD sensing. Transient or permanent loss of capture or sensing of the pacemaker was not observed after ICD shocks with the output programmed to double pulse width and voltage of stimulation threshold and the sensitivity to 50% of the detected R wave. One episode of transient reprogramming occurred without clinical consequences. One unipolar ventricular pacemaker lead had to be exchanged against a bipolar lead because of oversensing of the pacing artifact by the ICD. There was no failure of an ICD to detect ventricular arrhythmias due to inadequate pacemaker activity. During a follow-up period of 21 +/- 11 months, a total of 78 ventricular arrhythmias were effectively treated in six patients. Thus, a combined use of transvenous ICD and pacemaker is possible despite the close vicinity of pacing and defibrillations leads. Optimized programming different to the common settings is required. As interactions occurred only in unipolar pacemaker leads bipolar systems should be used in these patients.