Combined Use of a True-Bipolar Sensing Implantable Cardioverter Defibrillator in a Patient Having a Prior Implantable Spinal Cord Stimulator for Intractable Pain

Reported is a case involving a patient with a previously implanted spinal cord stimulator (SCS) who presented for an implantable. Cardioverter defibrillator (ICD). The SCS device was located in the left lower abdominal quadrant with a stimulation electrode array placed on the dorsal aspect of the spinal cord at the T-11 thoracic level. Interaction testing demonstrated that the bipolar sensing transvenous ICD system (Medtronic 7221Cx PCD) did not detect the stimulator's output at burst rates ranging from 20–130 pulses/s, even with the ICD set to its maximum sensitivity of 0.15 mV and the stimulator programmed to the highest patient tolerated output combinations of 5 V, 0.45 ms in the bipolar configuration and 3 V, 0.45 ms in the unipolar (i.e., case-electrode) configuration.     

The Effects of Nuclear Magnetic Resonance Imagers on External and Implantable Pulse Generators

This study evaluates the effect of nuclear magnetic resonance (NMR) scanning on pacemaker function. It must be emphasized that each manufacturer's pulse generators and each pacing modality may behave differently and, therefore, require individual evaluation. According to our results, patients with pacemakers should have their pacing activity monitored continuously during scanning with the NMR 1500 gauss imaging system. External pulse generators should be set to the asynchronous mode and placed outside the NMR image volume but within the radiofrequency (RF) shield. Implanted pacemakers should be verified for type and mode of operation. All implantable pulse generators evaluated reverted from the demand to the asynchronous mode within the magnetic field of the scanner. There was no observable damage to the discrete pacemaker components that were tested. In vivo testing of implantable single-chamber pulse generators did not significantly alter the pacemaker's operating parameters. Changes in stimulation rate analogous to the RF field pulse rate were seen. In single-chamber devices the resultant rate was a multiple of the RF frequency, changing to a value less than the normal asynchronous magnetic rate. With more sophisticated dual-chamber devices the results varied. With VDD pacing during RF scanning, the cardiac stimulation rate increased to a value analogous to the RF field modulation period. More extensive in vivo testing using different models of pulse generators of various manufacturers is needed to identify specific device susceptibility to the RF, time variance and steady-state magnet fields. From these data a comprehensive statement about NMR scanning of patients with implanted pacemakers can be made.     

ICD and Neuromodulation Devices: Is Peaceful Coexistence Possible?

Aim: The aim of this study was to investigate the potential cross‐talk between implantable cardioverter defibrillator device (ICD) and implantable neuromodulation device (IND) during the implantation procedure and the ventricular fibrillation induction test and in daily life. Methods: We present two cases of patients with an IND who underwent ICD implantation and one case of a patient implanted with a biventricular ICD who received an IND 6 months later. Two of these patients had a spinal cord stimulator (SCS), while the other had a sacral neuromodulator. Results: No cross‐talk was recorded in the patient with the sacral neuromodulator and the ICD. Temporary damage to one of the SCSs was observed after multiple ICD shocks. Conclusions: When implanted contemporarily with sacral or spinal neurostimulators, cardiac devices appear to be safe, as confirmed by the appropriate detection and interruption of arrhythmic episodes. On the other hand, neuromodulation devices could be temporarily or permanently damaged by multiple ICD discharges. It is recommended that the neurostimulator be interrogated after an ICD shock, in order to check the state of the device. (PACE 2011; 690–693)     

Use of an implantable cardioverter defibrillator in a patient with two implanted neurostimulators for severe Parkinson's disease

We report a patient with Parkinson's disease treated with two pectorally implanted neurostimulators (NSs) who presented with a life-threatening ventricular tachyarrhythmia in whom an abdominal ICD was implanted. Testing during implantation showed that the NS did not affect the bipolar sensing of the ICD, even when the NSs were set at a frequency of 130 pulses/s with an output of 5 V and pulse width of 0.21 ms in a bipolar and a unipolar configuration. The ICD shock, however, did affect both NSs: there was a reset to the output Off state and there was a reset of the electrode polarities.     

A New Advancement in Noninvasive Electrophysiology: A Standard Laboratory Stimulator Pulse Coupled with an Implanted Pacemaker

A new device for coupling the pulse from a standard laboratory stimulator to commercially available implanted pacemakers for use in noninvasive electrophysiology testing has been developed. When programmed to an electrophysiology mode, a 37 kHz carrier wave, generated by the programmer, maintains communication with the implanted pacemaker. Stimuli generated from a standard lab stimulator cause a break in the carrier wave and an output from the pacemaker. Cycle lengths as short as 127 msec can be attained. In addition to standard electrophysiology testing, this noninvasive electrophysiological technique can be used to fibrillate the heart to test the efficacy of automatic implantable cardioverter/defibrillators.     

Laminated pyroelectric generator with spin coated transparent poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) electrodes for a flexible self-powered stimulator

Implantable devices are promising electronics in medicine, which can perform real-time monitoring for a variety of human-body physiological conditions and control the function of some failing organs. However, the technology to power implantable devices still has some remaining challenges. This work presents a transparent self-powered pyroelectric generator driven by near infrared radiation for wireless powering of electronics. The pyroelectric device uses a highly conductive polymer, PEDOT:PSS, formed as an electrode without the use of a complex transferring process. Due to the good match between the surface energy of the PEDOT electrode and PVDF, when combined with PVDF the resulting PEDOT/PVDF/PEDOT device possesses a highly adherent interface. The influence of the PEDOT thickness on the output voltage of the device has been investigated according to the difference in its infrared transmittance and absorbance. In addition, in order to enhance the output voltage while reducing the device temperature, a laminated pyroelectric generator, in which each cell is composed of a PEDOT/PVDF/PEDOT sandwich, was further developed taking advantage of the high infrared transmittance of PEDOT and PVDF. The proposed laminated pyroelectric device could generate up to 23.4 V with six laminated cells, an enhancement of approximately 212% compared to a single cell, which could directly light up an LCD and was applied for nerve stimulation of the sciatic nerve of a frog, indicating that the proposed self-powered device could be a candidate for implantable medical electronics.

A laminated pyroelectric generator with spray coated transparent PEDOT:PSS electrodes has been designed for use as a flexible self-powered stimulator.     

Use of a Wireless Implantable Cardioverter Defibrillator in a Patient with a Preexisting Neurostimulator

We report the case of a 54-year-old man with a previously implanted neurostimulator who presented with palpitations and was found to have sustained ventricular tachycardia on electrophysiologic study. A Medtronic wireless implantable cardioverter defibrillator (ICD; Medtronic Inc., Minneapolis, MN, USA) with home monitoring (HM) was successfully implanted. Interaction testing during implantation, follow-up, and HM showed that there was no device-device interaction.     

Survival of Implantable Pacemaker Leads

FURMAN, S., ET AL.: Survival of Implantable Pacemaker Leads. Early polyurethane leads were reported to have a high incidence of materials failure. In 1979 a six-center registry was begun. By October 31, 1989, 7, 311 leads had been registered and lead longevity was calculated by individual manufacturer, cumulatively for all manufacturers and for individual leads. Each lead was registered at implant and at removal from service as having been removed for materials failure or for unrelated reasons. Calculations were made for 23 models and for a total of three manufacturers with more than 100 leads implanted. Four thousand seven hundred and sixty three leads (65.1%) were from Medtronic; 2, 177 (29.8%) from Cordis; 297 (4.1%) from Intermedics; and 77 (1.0%) were from all others. The 10-year cumulative survival of Medtronic leads was 96.6 ± 0.4%; for Cordis leads it was 99.9 ± 0.1% and for Intermedics leads 97.7 ± 0.9%. Three lead models registered over 100 units and had poorer survival at 5 years than the remainder of all manufacturers' experience. They were #6972 (n = 107) with 78.6 ± 4.5%; #6991U (n = 294) with 90.6 ± 1.9%; and #4012 (n = 288) with 97.3 ± 1.5%. Other possibly failed models did not achieve statistical significance. It can be anticipated that a lead which survives to the seventh year will have prolonged longevity as thereafter additional failures are uncommon.     

Assessment of Long-Term Stability of Chronic Ventricular Pacing Thresholds in Steroid-Eluting Electrodes

Sixteen patients with Medtronic 4003 steroid-eluting electrodes implanted in the ventricular position were followed over 5 years. In each patient a special type of Medtronic 2443 pacemaker was implanted to allow programming of output at 1.35 V. Chronic threshold values in these patients measured at an output of 1,35 V were stable over the first 18 months of follow-up. Mean values were: 0.06 ± 0.03 msec at 6 months and 0.08 ± 0.02 msec at 18 months; these did not differ from each other significantly. However, during the period from 18 to 36 months postimplantation, a significant increase in mean pacing threshold was observed: 0.08 ± 0.02 msec at 18 months postimplantation versus 0.14 ± 0.05 msec at 36 months (P < 0.01), After 36 months, the chronic pacing threshold remained stable until the end of the 5-year follow-up period. Further long-term study of chronic threshold behavior of steroid-eluting electrodes measured at low amplitudes is warranted.     

Acute and Chronic Pulse-Width Thresholds in Solid Versus Porous Tip Electrodes

Sixty-one patients given programmable pacemakers at initial implantation have been followed for a mean of 18 months (3-42) with non-invasive measurements of myocardial pulse-width threshold. Fifty of the patients had CPI 0505/0522 (Microlith-P/Microthin-PI) pacemakers with either Cordis 322-462 8 mm2 ball tip (n=12), Cordis 322-620 17.5 mm2 (n=23), or CPI 4116 porous tip electrodes (stimulation area 7.5 mm2 and sensing area 50 mm2) (n=15). Eleven patients had Medtronic 5985 (Spectrax-SX) pacemakers with either Medtronic 6907-R 8 mm2 ring tip (n=7), 6907 11 mm2 (n=3) or 6917 myocardial electrodes (area 12 mm2) (n=1). At acute implant, the ball tip and porous tip electrodes had the lowest stimulation thresholds, but the differences were only statistically significant in comparison with the 17.5 mm2 electrode (p less than 0.01). Chronically there were no significant differences between the various electrodes (p greater than 0.1), but the ball tip electrode tended to give best long-term results, and the porous tip electrode the poorest. Thirty-eight of the 61 patients (62.3%) had chronic pulse-width thresholds of 0.1 ms or less at approximately equal to 5 V output, indicating that pulse-width programming is a useful way to conserve battery energy. However, at some stage of the study, six of the patients (9.8%) had a pulse-width threshold of 0.5 ms or more. Pulse width should therefore not be set too narrow in standard nonprogrammable pacemakers.     

Spinal Cord Stimulation for Complex Pain: Initial Experience with a Dual Electrode, Programmable, Internal Pulse Generator

Abstract: The objective of this study was to engage in an 18‐month follow‐up of 20 chronic complex pain patients using a dual electrode, programmable, fully implantable internal pulse generator (IPG) for spinal cord stimulation (SCS). Implant status, stimulation mode, anode‐cathode configuration (array), cathode position, paresthesia overlap, complications, Visual Analog Scores (VAS), and overall satisfaction were prospectively examined in 20 patients implanted with dual 4 contact, staggered, percutaneous electrodes (Pisces 3487A, Medtronic, Minneapolis, Minnesota) internalized to a fully implantable, programmable IPG (Synergy 7466, Medtronic, Minneapolis, Minnesota). All patients had undergone initial implantation for chronic complex axial and extremity pain (eg, Failed Back Surgery Syndrome (FBSS), Complex Regional Pain Syndrome (CRPS)) with dual octapolar, radiofrequency (RF) SCS systems (Advanced Neuromodulation Systems 2098, Plano, Texas). 1 - 3 All patients required conversion to the current dual IPG systems due to RF system receiver sensitivity, preventing further antenna coupling). 1 Dual quadrupolar IPG SCS outcomes were compared to previous long‐term, dual octapolar RF SCS complex pain reports. 1 - 3 Data was collected and analyzed by a disinterested third party. At 18 months, all 20 patients remained implanted. All patients reported using 1 or 2 “best” guarded tripolar or bipolar arrays to maintain favorable paresthesia overlap (77.5%), VAS reduction (9.78 → 4.40), and overall patient satisfaction (80%). Eighty‐five percent of “best” anode‐cathode configurations were activated on both electrode columns about the physiologic midline of the C 3/4 vertebral segments for upper extremity pain, and the T 9/10 vertebral segments for low back and lower extremity pain. Sixty‐seven and one half percent of all electrodes were thoracic and 32.5% were cervical. “Best” arrays were activated as narrow (adjacent contact) guarded cathode tripoles (75%), extended (nonadjacent contact) bipoles/tripoles (15%), or as narrow bipoles (10%). The mean number of active contacts per “best” array was 5.6, with 3.75 anodes and 1.85 cathodes. All patients preferred the current IPG to the prior RF SCS implant, citing RF receiver site sensitivity, difficulty maintaining coupling of the RF antennae, and time intensive RF programming. Conversely, 13 patients (65%) reported IPG site sensitivity that did not affect overall satisfaction. That is, none would convert their current IPG to a smaller IPG to resolve this issue, unless it was of equal longevity. Sixteen patients (80%) were satisfied with the overall level of pain relief, and all (100%) would repeat the IPG SCS implant. This study demonstrates improved overall outcome and patient satisfaction after long‐term, dual octapolar RF SCS conversion to dual quadrupolar IPG SCS systems in the same patient population. It also validates prior dual SCS electrode reports of common array configuration, electrode positioning about the physiologic midline, and patient preference of single or dual programmability in the treatment of chronic complex pain. 1 , 4 , 5 Follow‐up of this initial experience with a multicenter study is warranted.     

Complications with the MICRA TPS Pacemaker System: Persistent Complete Heart Block and Late Capture Failure

A Medtronic MICRA transcatheter pacing system (Medtronic, Minneapolis, MN, USA) was implanted in an 86‐year‐old patient with sick sinus syndrome and left bundle branch block after transfemoral aortic valve implantation. During implantation she developed a persistent complete heart block due to manipulation with the large‐bore delivery catheter. Two weeks later, acute pacemaker dysfunction occurred due to massive increase of pacing threshold and impedance without obvious pacemaker dislocation or myocardial perforation. Recurrent capture failure was seen with pacing output set at 5 V/1.0 ms. Hence, microdislocation or fixation of the tines in the right ventricular trabeculae has to be assumed.     

Pacing Threshold Trends and Variability in Modern Tined Leads Assessed Using High Resolution Automatic Measurements: Conversion of Pulse Width into Voltage Thresholds

With the aid of an algorithm for automatic pacing threshold (T) measurement in the atrium and ventricle, downloadable into implanted Thera pacemakers (Medtronic Inc.), we studied T evolution during lead maturation, T variation during activities of daily living, and various types of beat-to-beat T variations in three tined bipolar leads: 5.6-mm² steroid-eluting (Medtronic Inc. models 4524 atrial-J [n = 8] and 4024 ventricular [n = 8]), 1.2-mm² steroid-eluting (Medtronic Inc. models 5534 atrial-J [n = 9] and 5034 ventricular [n = 9]), and 8-mm² without steroid (Intermedics models 432–04 atrial-J [n = 7] and 430–10 ventricular [n = 7]). The leads were implanted in 24 consecutive patients with intact AV conduction (required by the algorithm) and followed for up to 13–25 months after implantation. Since the algorithm determined pulse width Ts at different amplitudes that, depending upon T level, could range from 0.5 to 5.0 V, we invented a methodology for conversion of pulse width Ts into voltage Ts at 0.5 ms, to pool and present T data on a universal scale. Frequent, high resolution T measurements revealed details on the lead maturation process that we divided into three stages: initial T subsiding, first wave of T peaking, and a new, quicker or slower, T rise. Although there were notable differences in duration and magnitude of T peaking on the individual basis, differences between the three lead types and between the atrium and ventricle were demonstrable. The 1.2-mm² leads exhibited less T peaking than their predecessors 5.6-mm² leads and excellent positional stability, whereas 8-mm² leads demonstrated the most intensive T peaking and highest mean chronic T values. T changes during activities of daily living showed some tendencies—higher T during night and lower T during exercise —yet with a number of exceptions. The overall magnitude of daily T fluctuations was < 0.2 V in all but one lead, and 50% daily voltage safety margin would be sufficient. A 100% voltage safety margin may be inadequate for a 1-year period during the chronic phase (after 6 months of implantation). A scheme for calculation of pulse width safety margins equivalent to voltage safety margins is given. Some leads can exhibit very large beat-to-beat T variations before, during, and after T peaking, and prospective algorithms for automatic T measurement should verify T values through more than 1–2 captured beats to obviate a great underestimation of the T providing consistent capture. T dependence upon pacing rate was negligible. Consistent-capture hysteresis may, in conjunction with lead instability, be as much as 0.25 V. Therefore, it is better to use an incremental approach from below to T level during automatic T measurements.     

Time Dependent Variations of Stimulus Requirements in Spinal Cord Stimulation for Angina Pectoris

The aim of the study was to observe changes over time of the stimulation requirements in spinal cord stimulation (SCS). Of 60 patients treated with SCS, 25 patients were selected because they had neurostimulators capable of measuring impedance noninvasively, and had not experienced electrode displacement. All 25 patients had Medtronic Pisces Quad 3487A (Medtronic, Inc.) neuroelectrodes with the tip positioned in the thoracic epidural space. The accuracy of the neurostimulators impedance measuring circuit was investigated in a test circuit. The error was < 11%. Stimulus requirements and impedance were recorded at the implantation and at follow-ups during a period of 24 months. During the first month after implantation, the stimulus requirements for satisfactory effect varied between +406% and -34%. After that period, only minor deviations were observed in most patients. To optimize the pain reducing effect of the spinal cord stimulation, frequent follow-ups are recommended during the first month; later on, the follow-up intervals can be extended. No tolerance development or pain resistance developed during SCS treatment     

Safety and Management of Implanted Epilepsy Devices for Imaging and Surgery

Permanently implanted devices that deliver electrical stimulation are increasingly used to treat patients with drug-resistant epilepsy. Primary care physicians, neurologists, and epilepsy clinicians may encounter patients with a variety of implanted neuromodulation devices in the course of clinical care. Due to the rapidly changing landscape of available epilepsy-related neurostimulators, there may be uncertainty related to how these devices should be handled during imaging procedures and perioperative care. We review the safety and management of epilepsy-related implanted neurostimulators that may be encountered during imaging and surgery. We provide a summary of approved device labeling and recommendations for the practical management of these devices to help guide clinicians as they care for patients treated with bioelectronic medicine.     

Focal hepatic lesions: Detection by dynamic and delayed computed tomography versus short TE/TR spin echo and fast field echo magnetic resonance imaging

Eighteen patients with focal hepatic lesions were evaluated with two computed tomographic (CT) techniques including dynamic sequential bolus contrast CT and delayed contrast CT, and 3 magnetic resonance (MR) techniques including a spin echo pulse sequence with TE/TR of 21/310 msec and 2 fast field echo sequences using a TE/TR of 15/300 msec and 80° flip angle (T1-weighted) and TE/TR of 15/500 msec and 10–20° flip angle (T2-weighted). We concluded that CT, using delayed contrast and dynamic sequential bolus contrast techniques, was consistently superior to the 3 MR pulse sequences used on our imagers in terms of number of lesions detected, lesion-to-liver contrast, and quality of scan.     

The effect of power frequency high intensity electric fields on implanted cardiac pacemakers

Thirty-five patients fitted with 16 different pacemaker models (from 6 manufacturers) were exposed to 50 Hz electric fields up to a maximum of 20 kV/m. Four different response patterns were encountered: (1) normal sensing and pacing in all Medtronic and some Vitatron units; (2) reversion to the fixed (interference) rate in all Telectronics, all Pacesetter, some Vitatron and CPI units; (3) slow and irregular pacing in one CPI and in all Cordis units; (4) mixed behavior over a critical range of field strengths in which slow and irregular pacing preceded reversion to fixed-rate, in some Telectronics and Pacesetter units. The field strengths required to induce such behavior varied from unit to unit and from model to model, with Telectronics being the most sensitive. In general, the interference threshold depended on the magnitude and distribution of induced body current relative to the pacemaker as well as field strength and thus varied with patient height, build and posture. While only a small proportion of pacemaker patients are likely to encounter electric fields strong enough to interfere with pacemaker behavior, this possible hazard should be recognized.     

Interaction Between Electronic Article Surveillance Systems and Implantable Defibrillators: Insights from a Fourth Generation ICD

We present a case report of an inappropriate discharge from a fourth generation implantable cardioverter defibrillator (ICD) as a result of exposure to electromagnetic interference. A 60-year-old man implanted with a Medtronic 7219D defibrillator experienced shocks without preceding symptoms while walking through an electronic surveillance system in a store. Though this has been reported, the mechanism of the interaction remains unexplained. The electrogram storage capabilities of this particular device enabled us to establish that this resulted from inappropriate sensing of the electromagnetic interference.     

兔VX2种植性肝癌模型不同生长期的常规MR和扩散加权成像与病理对照

目的初步探讨DWI对监测兔VX2种植性肝癌模型生长特点的价值。方法新西兰大白兔44只,采用开腹下瘤组织块穿刺接种法,每只实验兔接种1个部位,将成功建立模型的38只实验兔随机分为两组(14d组和22d组),分别在规定的时间内行常规MR序列和DWI检查(b=1000s/mm2),分别获得不同时间点肿瘤的ADC图,并对全部肿瘤标本按扫描方向切层并行大体病理检查。结果①两组肿瘤在DWI上均呈明显高信号,与周围肝实质形成鲜明对比;②14d组所有肿瘤的ADC图信号均匀,大体病理显示所有肿瘤质地均匀,无坏死囊变区,与ADC图表现一致;22d组所有肿瘤中心部分在ADC图上均可见斑片状坏死囊变区的信号,且与大体病理所显示的范围基本一致,而在常规T2WI上仅有4例肿瘤中心可见斑片状高信号。结论DWI检查的ADC图可敏感检出肿瘤的坏死囊变区,在动态追踪肿瘤发生、发展和生长特性方面具有重要的价值,是常规MR检查的有益补充。     

Technische Entwicklung der spinalen Neurostimulation

The rationale for the use of spinal cord stimulation (SCS) in the treatment of chronic pain arose from Melzack and Wall's gate theory of the control of pain (1965). Originally electrodes were placed directly on the spinal cord via open operation, while now they are placed by means of direct puncture the epidural space. In most cases, one of two different systems is used: (1) semi-implants, consisting of an implantable electrode, connection cable and receiver, and externally worn stimulator with antenna; (2) full implants, consisting of an implantable electrode, connection cable and a stimulator, which is also implanted. The implantation of an SCS system is a surgical procedure, which requires the highest standards in asepsis. The operation and its complications and ways of avoiding them are described.