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)     

Simple Method to Eliminate Interference between Ventricular Assist Devices and Cardiac Rhythm Devices

Background: Report on a simple solution to allow programming of defibrillators in the presence of a Heartmate II (Thoratec Corporation, Pleasanton, CA, USA) ventricular assist device. Ventricular assist devices have become increasingly utilized for patients waiting for heart transplantation as well as those who will be maintained on a permanent support. The Heartmate II, which was recently given Food and Drug Administration approval as a bridge-to-transplant device, has a particular anomaly that complicates patient management. The pulse width modulator of the Heartmate II produces electromagnetic noise that interferes with the ability to interrogate and program certain defibrillators, and explantation of the defibrillator has been reported as the only viable solution.
Methods: The authors describe the use of cast-iron pans to reduce the electromagnetic interference between St. Jude Medical's first-generation Atlas family of defibrillators (St. Jude Medical, St. Paul, MN, USA) and the Heartmate II pump.
Results: The use of a simple shielding protocol avoids the need to remove a pre-existing defibrillator from a patient receiving support from the Heartmate II ventricular assist device.
Conclusions: The method described herein is important as future generations of medical devices may present different types of device-device interactions. Simple bedside methods to eliminate interference can potentially help patients who would otherwise need one or another device removed     

Functional Atrial Undersensing Associated with Switching to a Tracking Mode of Pacing

We have previously demonstrated that contemporary St. Jude devices (pacemakers and implantable cardioverter‐defibrillators [ICDs]; St. Jude Medical, Sylmar, CA, USA) are designed to generate an extended postventricular atrial refractory period (PVARP) of 475 ms at the termination of conventional automatic mode switching (AMS) in response to atrial tachyarrhythmias . This response may cause functional atrial undersensing . A similar PVARP response unrelated to conventional AMS was found in four St. Jude devices (three ICDs and one pacemaker) whenever a nontracking pacing mode switched to a tracking DDD(R) mode. PVARP extension and functional atrial undersensing were observed when the VOO, VVI, and the DDI(R) modes (unrelated to conventional AMS) switched to the DDD(R) mode . In one patient the switch from the OOO mode (in the programmed noise reversion mode) to the DDD mode occurred after cessation of electromagnetic interference disturbing the ventricular channel. In this case PVARP extension was seen only in the corresponding markers because no P waves occurred coincidentally with the extended PVARP. The PVARP extension caused by a mode switch to the tracking function was designed to prevent sensing of a retrograde P wave on the first cycle of the reestablished tracking mode. The observed functional atrial undersensing is a normal manifestation of device function and must not be misinterpreted as a true atrial undersensing problem. (PACE 2012; 35:1188–1193)     

Significance of missing telemetered markers in implanted cardioverter-defibrillators

Background: We report three patients with St Jude ICDs (St. Jude Medical, Sylmar, CA, USA) where some aspect of the marker channel was missing. Methods and Results: Two cases were caused by the simultaneous occurrence of two distinct cardiac or device events that affected the proper delivery of markers by the telemetry system. Inability of the devices to sequentially process these events resulted in incomplete transmission of telemetry data to the programmers and caused missing markers in the telemetry recordings. In the third case, sensed atrial interference resulted in a short period of atrial asynchronous pacing, which prevented the delivery of a sensed atrial marker coincident with an atrial electrogram. This atrial electrogram by virtue of its timing would have otherwise been sensed outside the atrial refractory period. Conclusion: The perplexing recordings of the three patients should not be interpreted as representing true pacemaker malfunction. PACE 2012; 35:409–415)     

Prevention of inappropriate ICD shocks due to lead insulation failure by continuous monitoring and automatic alert

Patients with implantable cardioverter defibrillator lead insulation failures may present with oversensing and/or abnormal impedance. The Lead Integrity Alert (LIA) monitors right ventricular pace/sense leads using both continuous oversensing and daily impedance measurementd. Oversensing consists of isolated short R‐R intervals and nonsustained runs of short R‐R intervals. The LIA algorithm has been studied for Sprint Fidelis conductor fractures, but not for lead insulation failures. We report on a patient with a failed St. Jude Riata? ST lead (St. Jude Medical, St. Paul, MN, USA) connected to a Medtronic Virtuoso DR (Medtronic Inc., Minneapolis, MN, USA) with the LIA. Oversensing triggered the LIA, while the impedance trend was normal. (PACE 2012; 35:e150–e153)     

Sudden and Fatal Malfunction of a Durata Defibrillator Lead due to External Insulation Failure

Defibrillator lead malfunction can be a disastrous complication, leading to loss of protection from sudden cardiac death in a high‐risk patient population. Recognition of lead‐specific risk for failure can assist in development of focused screening or surveillance, as in the case of the Riata lead (St. Jude Medical, St. Paul, MN, USA) or the Sprint Fidelis lead (Medtronic Inc., Minneapolis, MN, USA). A case of defibrillation failure secondary to a Durata lead insulation failure is presented. A brief review of the literature and current St. Jude Medical implantable cardiac defibrillator lead design is presented. Identification of arcing is identified as a potential sign of catastrophic insulation failure.     

Acute Perforation in Spite of Implantation with an “Antiperforation” Defibrillator Lead

A 74‐year‐old male underwent implantation of implantable cardioverter defibrillator per multicenter automatic defibrillator trial two criteria. The new St. Jude Medical Riata STS Durata defibrillator lead (St. Jude Medical, Sylmar, CA, USA) was used. This lead has a slight curve at the right ventricle shock coil and a silicone tip designed to decrease tip pressure at the endocardium interface. We presented a case of acute perforation during implantation of this lead. The patient was treated with pericardiocentesis and recovered.     

Combining electromagnetic navigation and 3‐D mapping to reduce fluoroscopy time and achieve optimal CRT response

Implantation of cardiac resynchronization therapy (CRT) devices can be challenging, time consuming, and associated with high‐dose x‐ray exposure. We present the technique in which an electromagnetic navigation system (MediGuideTM, St. Jude Medical) and an electroanatomical three‐dimensional mapping system (EnSite NavX, St Jude Medical) are usefully combined for implanting implantable cardioverter defibrillator CRT devices with strong reduction of x‐ray exposure, and for targeting the most delayed regions in the activation maps avoiding scars for optimal CRT response.     

Unusual ECG Pattern of Right Atrial Appendage Atrial Tachycardia in One Patient with Right Pneumonectomy

The right atrial appendage atrial tachycardia (RAA AT) has been previously reported as a rare site in focal AT. We report a patient with a history of a right pneumonectomy who underwent catheter ablation of the AT originating from the RAA. This RAA AT showed unusual P‐wave morphology compared with previous reports. We describe the RAA AT following right pneumonectomy using a NavX system (St. Jude Medical, St. Paul, MN, USA). (PACE 2010; e46–e48)     

Electrical Dysfunction Associated with Conductor Externalization of a Silicone Left Ventricular Lead

The St. Jude Medical QuickFlex LV lead family (St. Jude Medical, Inc., St. Paul, MN, USA) has been placed under advisory by the manufacturer due to a reported small number of cases of outer insulation failure and conductor externalization. There have been no reports of alteration of any electrical parameters associated with externalization. In this report, a sudden drop of impedance and rise in capture threshold of the left ventricular ring electrode is described, associated with the corresponding externalization of the inner conductor cables confirmed on physical examination. Flexion or torsion of lead was demonstrative of forces favoring externalization of inner conductor cables. Saline bath testing revealed a reproducible, transient reduction in lead resistance associated with conductor externalization. Close monitoring of electrical performance of this lead family is indicated.     

Comparison of transesophageal color flow Doppler imaging of normal mitral regurgitant jets in St. Jude Medical and Medtronic Hall cardiac prostheses.

Transesophageal color flow Doppler imaging of mitral mechanical prostheses is now widely used. This method eliminates the frequent problems of acoustic shadowing and flow masking that are commonly seen with a transthoracic Doppler study of mechanical mitral prostheses. Transesophageal color flow Doppler imaging was performed postoperatively in seven patients who had received St. Jude Medical mitral prostheses (St. Jude Medical, Inc., St. Jude, Minnesota) and in six patients who received Medtronic Hall mitral valves (Medtronic, Inc., Minneapolis, Minnesota). Maximal systolic regurgitant jet length and area determinations were obtained in all patients. A comparison of maximal jet lengths and areas for each type of mechanical prosthesis demonstrated that the Medtronic Hall prostheses produced longer maximal jet lengths (p = 0.0001) and larger jet areas (p = 0.0009) than those produced by the St. Jude Medical mitral valves. Medtronic Hall prostheses produce a large centrally directed jet, whereas St. Jude Medical prostheses typically generate three smaller jets. Recognition of these differences in transesophageal color flow Doppler images in these commonly used cardiac valve prostheses is necessary to avoid misinterpretation of the normally large systolic regurgitant jet of the Medtronic Hall prosthesis as representing prosthetic dysfunction.     

Delayed ICD lead cardiac perforation: comparison of small versus standard-diameter leads implanted in a single center

Background: An increased risk of delayed cardiac perforation (DCP) with active‐fixation small‐diameter ICD leads has recently been reported, especially with regard to the St. Jude Riata lead (St. Jude Medical, Sylmar, CA, USA). Few data on the risk of DCP in small versus standard‐diameter leads implanted in a single high‐volume center are available. Moreover, no data on the performances of St. Jude's new small‐diameter Durata lead are as yet available. The aim of this study was to assess the incidence of DCP in small versus standard‐diameter leads implanted in our center. Methods: Between January 2003 and October 2009, 437 small‐diameter leads (190 Medtronic Sprint Fidelis [Medtronic Inc., Minneapolis, MN, USA], 196 Riata, 51 Durata) and 421 standard‐diameter (>8 Fr) leads were implanted. Results: After a median follow‐up of 421 days seven of 858 (0.8%) patients experienced DCP. The incidence of DCP was higher in patients with small‐diameter leads than in those with standard‐diameter leads (1.6% vs 0%, P = 0.01). No cases of DCP occurred among 371 passive‐fixation leads versus 1.4% of events among active‐fixation leads (P = 0.02). The incidence of DCP was 2.5% in Riata, 1% in Sprint Fidelis, 0% in Durata, and 0% in standard‐diameter leads (P < 0.01 for Riata vs standard‐diameter leads). Conclusions: Small‐diameter active‐fixation ICD leads are at increased risk of DCP, a finding mostly due to the higher incidence of events in the Riata family. By contrast, passive‐fixation small‐diameter leads and standard‐diameter leads appear to be safe enough regarding the risk of DCP. Our preliminary data suggest that the new Durata lead is not associated with an increased risk of DCP. (PACE 2011; 34:475–483)     

Update on small-diameter implantable cardioverter-defibrillator leads performance

Background: The performance of small diameter implantable cardioverter defibrillator (ICD) leads is questionable. However, data on performance during long‐term follow‐up are scarce. The aim of this study is to provide an update for the lead failure and cardiac perforation rate of Medtronic's Sprint Fidelis ICD lead (Medtronic Inc., Minneapolis, MN, USA) and St. Jude Medical's Riata ICD lead (St. Jude Medical Inc., St. Paul, MN, USA). Methods: Since 1996, all ICD system implantations at the Leiden University Medical Center, the Netherlands, are registered. For this study, data up to February 2011 on 396 Sprint Fidelis leads (follow‐up 3.4 ± 1.5 years), 165 8‐French (F) Riata leads (follow‐up 4.6 ± 2.6 years), and 30 7‐F Riata leads (follow‐up 2.9 ± 1.3 years) were compared with a benchmark cohort of 1,602 ICD leads (follow‐up 3.4 ± 2.7 years) and assessed for the occurrence of lead failure and cardiac perforation. Results: During follow‐up, the yearly lead failure rate of the Sprint Fidelis lead, 7‐F Riata lead, 8‐F Riata lead, and the benchmark cohort was 3.54%, 2.28%, 0.78%, and 1.14%, respectively. In comparison to the benchmark cohort, the adjusted hazard ratio of lead failure was 3.7 (95% confidence interval [CI] 2.4–5.7, P < 0.001) for the Sprint Fidelis lead and 4.2 (95% CI 1.0–18.0, P < 0.05) for the 7‐F Riata lead. One cardiac perforation was observed (3.3%) in the 7‐F Riata group versus none in the 8‐F Riata and Sprint Fidelis lead population. Conclusion: The current update demonstrates that the risk of lead failure during long‐term follow‐up is significantly increased for both the Sprint Fidelis and the 7‐F Riata lead in comparison to the benchmark cohort. Only one cardiac perforation occurred. (PACE 2012; 35:652–658)     

Erroneous Magnet Positioning Leads to Failure of Inhibition of Inappropriate Shock during Fast Conducting Atrial Fibrillation Episodes

We present the case of a 75‐year‐old patient with a single‐chamber St. Jude Medical internal cardioverter defibrillator (ICD; St. Jude Medical, St. Paul, MN, USA) for primary prevention, who was admitted with 39 inappropriate ICD shocks because of atrial fibrillation with rapid ventricular frequention, despite magnet placement. Review of the device manual and literature revealed that apart from different responses to magnet placement programmed for the various manufacturers, the type of magnet and the positioning can be of specific interest. In the case presented, the donut‐shaped magnet should have been placed off‐center instead of directly over the device.     

Strength Duration Curve for Left Ventricular Epicardial Stimulation in Patients Undergoing Cardiac Resynchronization Therapy

Introduction: The strength duration curve has been studied for right ventricular endocardial stimulation. There are differences between left ventricular epicardial and right ventricular endocardial stimulation due to different electrophysiologic properties and different electrode-tissue interface. The strength duration curve for epicardial left ventricular stimulation has not been studied so far.
Methods: One hundred and three patients were studied. The strength duration curves were determined for left ventricular epicardial and right ventricular endocardial stimulation. The studied points were chronaxie, rheobase, and voltage threshold at 0.5 ms. Left ventricular leads Guidant 4512, 4513, 4537, 4538 (unipolar, area 3.5 mm²; Guidant Corp., St. Paul, MN, USA), Medtronic 4193 (unipolar, area 5.8 mm²; Medtronic Inc., Minneapolis, MN, USA), Guidant 4518, 4542, 4543 (bipolar, area 4 mm²), St. Jude Medical (bipolar, area 4.8 mm²; St. Jude Medical, St. Paul, MN, USA), and Medtronic 4194 (bipolar, area 5.8 mm²) were studied.
Results: The Guidant unipolar leads with a distal electrode area of 3.5 mm² had a lower chronaxie than the other studied leads. The left ventricular epicardial and right ventricular endocardial chronaxie for 15 patients with Medtronic left ventricular leads 4194 or 4193 (5.8 mm²) and right ventricular leads 6947 (5.7 mm²) were 0.52 ± 0.36 ms and 0.62 ± 0.46 ms (P > 0.05).
Conclusion: The left ventricular epicardial chronaxie depends on the lead. The left ventricular epicardial chronaxie is similar to the right ventricular endocardial chronaxie for leads with similar electrode stimulation area.     

Shocking truths about implantable cardioverter defibrillator monitoring zones

A 36 year-old man with hypertrophic cardiomyopathy and an ATLAS + DR implantable cardioverter defibrillator (ICD) (St. Jude Medical, Inc., St. Paul, MN, USA) for primary prevention received a shock while cycling. The ventricular fibrillation detection threshold was 182 beats/min. An additional monitoring zone was programmed to 156 beats/min with all discriminators "on" except morphology. On interrogation, the ICD shock followed sinus tachycardia. In the absence of a monitoring zone, device therapy would not have been expected. We explore the mechanisms by which monitoring zones could potentially contribute to inappropriate ICD therapy and offer trouble-shooting tips.     

Diaphragmatic Myopotential Oversensing Caused by Change in Implantable Cardioverter Defibrillator Sensing Bandpass Filter

Diaphragmatic myopotential oversensing (DMO) causes inhibition of pacing and inappropriate detection of ventricular fibrillation in implantable cardioverter defibrillators (ICDs). It occurs almost exclusively with integrated bipolar leads and is extremely rare with dedicated bipolar leads. If DMO cannot be corrected by reducing programmed sensitivity, ventricular lead revision is often required. The new Low Frequency Attenuation (LFA) filter in St. Jude Medical ICDs (St. Jude Medical, Sylmar, CA, USA) alters the sensing bandpass to reduce T‐wave oversensing. This paper aims to present the LFA filter as a reversible cause of DMO. Unnecessary lead revision can be avoided by the simple programming solution of deactivating this LFA filter.     

Analysis of Implantable Defibrillator Longevity Under Clinical Circumstances: Implications for Device Selection

Introduction: Information about implantable cardioverter‐defibrillator (ICD) longevity is mostly calculated from measurements under ideal laboratory conditions. However, little information about longevity under clinical circumstances is available. This survey gives an overview on ICD service times and generator replacements in a cohort of consecutive ICD patients. Methods: Indications for replacement were classified as a normal end‐of‐service (EOS), premature EOS, system malfunction, infection and device advisory, or recall actions. From the premature and normal EOS group, longevity from single‐chamber (SC), dual‐chamber (DC), and cardiac resynchronization therapy defibrillator (CRT‐D), rate‐responsive (RR) settings, high output (HO) stimulation, and indication for ICD therapy was compared. Differences between brands were compared as well. Results: In a total of 854 patients, 203 ICD replacements (165 patients) were recorded. Premature and normal EOS replacements consisted of 32 SC, 98 DC and 24 CRT‐D systems. Longevity was significantly longer in SC systems compared to DC and CRT‐D systems (54 ± 19 vs. 40 ± 17 and 42 ± 15 months; P = 0.008). Longevity between non‐RR (n = 143) and RR (n = 11) settings was not significantly different (43 ± 18 vs. 45 ± 13 months) as it also was not for HO versus non‐HO stimulation (43 ± 19 vs. 46 ± 17 months). Longevity of ICDs was not significantly different between primary and secondary prevention (42 ± 19 vs. 44 ± 18 months). The average longevity on account of a device‐based EOS message was 43 ± 18 months. Average longevity for Biotronik (BIO, n = 72) was 33 ± 10 months, for ELA Medical (ELA, n = 12) 44 ± 17 months, for Guidant (GDT, n = 36) 49 ± 12 months, for Medtronic (MDT, n = 29) 62 ± 22 months, and for St. Jude Medical (SJM, n = 5) 31 ± 9 months (P < 0.001). Conclusion: SC ICD generators had a longer service time compared to DC and CRT‐D systems. No influence of indication for ICD therapy and HO stimulation on generator longevity was observed in this study. MDT ICDs had the longest service time.     

Transvenous Extraction Performance of Expanded Polytetrafluoroethylene Covered ICD Leads in Comparison to Traditional ICD Leads in Humans

Background: In the Endotak Reliance G defibrillating leads (Guidant Corporation, St. Paul, MN, USA), coils are covered with expanded polytetrafluoroethylene (ePTFE) to prevent tissue ingrowth. The aim of the study was to evaluate transvenous extraction performance, outcomes, and fibrotic adherences rate of ePTFE defibrillating leads in comparison to traditional non‐ePTFE cardiac defibrillator (ICD) leads. Methods: Seventeen consecutive ICD recipients (ePTFE Group A, 16 men, mean age 66 ± 12 years) with 17 Endotak Reliance G dual‐coil ICD leads (mean implantation time 23 ± 26 months) underwent a transvenous removal procedure. They were compared with two control groups, including 20 Sprint Quattro 6944 (non‐ePTFE Group B; Medtronic Inc., Minneapolis, MN, USA) and 36 Riata 1570 ICD leads (non‐ePTFE Group C; St. Jude Medical, St. Paul, USA). The indication for lead extraction was local infection in 35 patients (48%), sepsis in 24 patients (33%), and lead malfunction in 14 patients (19%). Results: In all groups, all leads were successfully and completely removed without major complications. Overall manual traction was effective in six patients (8%) and more effective in the ePTFE Group (29%) compared to Group B (0%) and Group C (3%) (P = 0.001). Sixty‐seven leads (92%) required mechanical dilatation by the venous entry site approach, with a shorter extraction time in the ePTFE Group (5 ± 11 min) compared to Group B (21 ± 22 min) and Group C (16 ± 22 min) (P = 0.003). ePTFE leads showed a lower rate of fibrotic adherences at the superior vena cava level (P = 0.01) without statistically significant differences in the other sites. Conclusions: ePTFE‐covered leads may be removed more easily and quickly than non‐ePTFE leads, requiring less frequently mechanical dilatation. (PACE 2010; 1376–1381)     

Electrical Failure of an ICD Lead due to a Presumed Insulation Defect Only Diagnosed by a Maximum Output Shock

A 55‐year‐old male patient presented after a single shock caused by oversensing of isolated nonphysiologic signals on both the distal HV and pace‐sense channels. No other abnormalities were found. He subsequently returned complaining of device “vibration” and his St. Jude implantable defibrillator (ICD; St. Jude Medical, St. Paul, MN, USA) was found to be in VVI backup mode and could not be interrogated. Direct testing in the electrophysiology lab showed normal lead impedances and thresholds with an inability to reproduce the abnormal signals. Detailed cine fluoroscopy of the leads found no abnormalities. A new ICD was connected and successfully delivered a 20‐joule shock but failed to deliver a maximum output (39‐joule) shock. The new ICD was again found to be in backup mode. A new Endotak Reliance G lead (Boston Scientific, Natick, MA, USA) was implanted and a maximum‐output shock was successful using a new Fortify DR ICD. This case likely represents a Durata lead insulation defect in the form of an inside‐out abrasion under the distal HV coil. Increased awareness of this defect is warranted, particularly since routine interrogation and submaximum‐output shocks may fail to detect the problem.