Predictors and mode of detection of transvenous lead malfunction in implantable defibrillators

Impact of ICD lead on the system durability, predictors of long-term survival following ICD system extraction

BACKGROUND

Implantable cardioverter-defibrillator (ICD) and cardiac resynchronization therapy defibrillator (CRT-D) systems are considered as having higher risk of complication and shorter durability but reasons of this multifactorial phenomenon remain unclear. We aimed to analyze this problem in population of patients with ICD leads referred for lead extraction (TLE).

METHODS

We have compared TLE indications, procedural results, and defined the long-term outcomes of TLE in patients with ICD/CRT-D devices (n  =  482, ICD (+)) with lead extractions in patients with standard pacemakers (n  =  1,402, ICD (-)). Demographic, clinical characteristics, and procedural outcomes were ascertained from single, primary operator registry. Long-term survival data were provided by the National Health Fund.

RESULTS

The ICD (+) subgroup had a significantly higher incidence rate of either infective or noninfective indications for TLE. The clinical success rate of extraction was 99.2% in ICD (+) versus 97.4% in ICD (-) (P  =  0.05) at a complication rate of 1.04% versus 2.14% (NS), respectively. In the median follow-up of 3.39 years, 142 patients from the ICD (+) subgroup and 303 from the ICD (-) subgroup died. The highest mortality rate of 41.1% was observed in the ICD (+) subgroup with infective indications. Infection, renal failure, diabetes, and age were the multivariate factors associated with increased mortality in the ICD (+) subgroup.

CONCLUSION

ICD leads remain more vulnerable, with respect to mechanical failure and their propensity to infection, in comparison to pacing leads. Their TLE is very effective at least complication rate, when performed by a highly skilled and experienced operator. However, long-term mortality after their TLE is high and is affected mostly by infections or patient-related factors.

Strategies for Transvenous Lead Extraction Procedures

Transvenous lead extraction (TLE) has undergone an explosive evolution since its inception as a rudimentary skill with limited technology and therapeutic options. Early techniques involved simple manual traction that frequently proved ineffective for chronically implanted leads, and carried a significant risk of myocardial avulsion, tamponade, and death. The morbidity and mortality associated with these early extraction techniques limited their application to use only in life-threatening situations, such as infection and sepsis. The past four decades, however, have witnessed significant advances in lead extraction technology, resulting in more efficacious techniques and tools, providing the skilled extractor with a well-equipped armamentarium. With the development of the discipline, we have witnessed a growth in the community of TLE experts coincident with a marked decline in the incidence of procedure-related morbidity and mortality, with recent registries at high-volume centers reporting high success rates with exceedingly low complication rates. Future developments in lead extraction are likely to focus on new tools that will allow for us to provide comprehensive device management, develop alternative systems for extraction training, and focus on the design of new leads conceived to facilitate future extraction.

A simple, wide bandwidth, biopotential amplifier to record pacemaker pulse waveform

Reliable detection of pacemaker pulses is getting more and more important in electrocardiography (ECG) diagnosis. Many studies recommend ECG amplifiers with higher bandwidth to prevent errors. In the past, few pilot studies showed that analysis of pacemaker pulses waveform can enhance diagnosis (eg, lead failure and fractured wire), but they were carried out with inadequate instrumentations for clinical practice. Typically, pacemaker pulses last hundreds of microseconds, edges of pulses elapse in few microseconds, and amplitude may exhibit large variations from few millivolts to volts. Pulse waveforms change often and depend on pacemaker type and programming. A simple, biopotential amplifier made of a few off-the-shelf components is proposed. The circuit fulfills specifications for biopotential amplifiers and offers a large bandwidth (~1 MHz). Therefore, it is able to accurately record time course of pacemaker pulses and allows highly accurate pulse detection and timing. Signals can be easily displayed and acquired by means of a standard, battery-powered oscilloscope. Pacemaker pulse vectorcardiography can be obtained by using two or more, wideband channels. Some exemplificative waveforms recorded during patient's periodic medical examination are reported. The proposed circuit offers simultaneous conventional ECG signal as an additional output.

Advances in sudden death prevention: the emerging role of a fully subcutaneous defibrillator

Randomized clinical trials support the use of implantable defibrillators for mortality reduction in specific populations at high risk for sudden cardiac death. Conventional transvenous defibrillator systems are limited by implantation-associated complications, infection, and lead failure, which may lead to delivery of inappropriate shocks and diminish survival. The development of a fully subcutaneous defibrillator may represent a valuable addition to therapies targeted at sudden death prevention. The PubMed database was searched to identify all clinical reports of the subcutaneous defibrillator from 2000 to the present. We reviewed all case series, cohort analyses, and randomized trials evaluating the safety and efficacy of subcutaneous defibrillators. The subcutaneous defibrillator is a feasible development in sudden cardiac death therapy and may be useful particularly to extend defibrillator therapy to patients with complicated anatomy, limited vascular access, and congenital disease. The subcutaneous defibrillator should not be considered in patients with an indication for cardiac pacing or who have ventricular tachycardia responsive to antitachycardia pacing. Further investigation is needed to compare long-term, head-to-head performance of subcutaneous defibrillators and conventional transvenous defibrillator systems.

Sports participation in patients with implantable cardioverter-defibrillators

The safety of sports participation for patients with implantable cardioverter-defibrillators (ICDs) is not yet defined, and current recommendations in both Europe and the US restrict these patients from competative sports more vigorous than golf or bowling. Postulated risks include increased frequency of arrhythmias, inability of the ICD to terminate ventricular arrhythmias during the metabolic changes accompanying extreme exercise, injury to the patient, or damage to the ICD system. However, survey data suggest that many ICD patients do participate in sports, and risks may be fewer than postulated. Ongoing research will better delineate the risks of sports for patients with ICDs.

Utility of postoperative testing of implantable cardioverter-defibrillators

BACKGROUND

Implantable cardioverter-defibrillators (ICDs) can provide life-saving therapies for ventricular arrhythmias. Arrhythmia induction and defibrillation threshold testing is often performed at implantation and postoperatively during long-term follow-up to ensure proper device function.

METHODS

We sought to evaluate the prevalence and predictors of occult device malfunction at follow-up defibrillation testing in asymptomatic individuals. A cohort of 853 patients underwent 1,578 defibrillation tests during the 13-year study period. Defibrillation efficacy was evaluated primarily by the two-shock (2S) method, with an adequate safety margin ≥ 10 joules (J) less than the maximum energy delivered by the ICD.

RESULTS

A total of 38 testing failures requiring intervention were discovered during testing (2.4% of all tests). There were 11 ICD system failures resulting in failure to defibrillate, six with underdetection of ventricular fibrillation, and 21 clinically significant increases in defibrillation threshold. There was a higher incidence of failure in older ICD systems (1996-2002) compared to newer ICD systems (2003-2009), reaching statistical significance (3.6% vs 1.0%; P < 0.01). There were 178 subjects (20.8%) with a >20-J safety margin on previous testing, detected R waves >7.0 mV, and all system components implanted after 2003 at the time of testing who did not have any testing failures (0% vs 5.6%; P < 0.01).

CONCLUSION

Postoperative defibrillation testing identifies a small number of ICD malfunctions in asymptomatic individuals. ICD testing failure is seen more frequently in older systems and in those with borderline results from prior interrogation or testing. These findings suggest that serial postoperative defibrillation testing is not indicated in asymptomatic patients without suspicion for specific problems.

Cost-effectiveness of implantable cardioverter-defibrillators in Brazil: primary prevention analysis in the public sector

BACKGROUND

Several studies have demonstrated the effectiveness and cost-effectiveness of implantable cardioverter-defibrillators (ICDs) in chronic heart failure (CHF) patients. Despite its widespread use in developing countries, limited data exist on its cost-effectiveness in these settings.

OBJECTIVE

To evaluate the cost-effectiveness of ICD in CHF patients under the perspective of the Brazilian Public Healthcare System (PHS).

METHODS

We developed a Markov model to evaluate the incremental cost-effectiveness ratio (ICER) of ICD compared with conventional therapy in patients with CHF and New York Heart Association class II and III. Effectiveness was evaluated in quality-adjusted life years (QALYs) and time horizon was 20 years. We searched MEDLINE for clinical trials and cohort studies to estimate data from effectiveness, complications, mortality, and utilities. Costs from the PHS were retrieved from national administrative databases. The model's robustness was assessed through Monte Carlo simulation and one-way sensitivity analysis. Costs were expressed as international dollars, applying the purchasing power parity conversion rate (PPP US$).

RESULTS

ICD therapy was more costly and more effective, with incremental cost-effectiveness estimates of PPP US$ 50,345/QALY. Results were more sensitive to costs related to the device, generator replacement frequency and ICD effectiveness. In a simulation resembling the MADIT-I population survival and ICD benefit, the ICER was PPP US$ 17,494/QALY and PPP US$ 15,394/life years.

CONCLUSIONS

In a Brazilian scenario, where ICD cost is proportionally more elevated than in developed countries, ICD therapy was associated with a high cost-effectiveness ratio. The results were more favorable for a patient subgroup at increased risk of sudden death.

Risk of failure of transvenous implantable cardioverter-defibrillator leads

BACKGROUND

Despite the positive effect on mortality in selected patients, implantable cardioverter-defibrillator therapy is also associated with potential malfunction of the implanted system. The present study provides the long-term lead failure rate in a large single-center cohort.

METHODS AND RESULTS

Since 1992, a total of 2068 implantable cardioverter-defibrillator patients with 2161 defibrillation leads were prospectively collected. Data of the implant procedure and all follow-up visits were recorded. All cases of lead removal or capping or placing of an additional pace or sense lead were noted and analyzed. Lead models were grouped by manufacturer and approximate lead diameter in French. During a mean follow-up of 36 months, 82 (3.8%) cases of lead failure were identified. Cumulative incidence of lead failure at 1 year was 0.6%; at 5 years, 6.5%; and at 10 years, 16.4%. The highest risk of lead failure was found in small-diameter leads. Adjusted hazard ratio was 6.4 (95% CI, 3.2 to 12.8) for Medtronic 7F leads, when compared with all other leads.

CONCLUSIONS

In this large single-center experience, the overall incidence of lead failure was 1.3 (95% CI, 1.0 to 1.6) per 100 lead-years. Comparison of different groups of leads shows major differences in event rates. Specific manufacturer's small-diameter defibrillation leads may have a higher risk of early lead failure.

[ICD lead defects: diagnosis and therapeutical options]

The number of cardioverter/defibrillator (ICD) implantations has been steadily increasing; thus, ICD lead-associated complications are an important issue. No clear recommendations for the diagnosis and management are available. This article gives an overview of how to diagnose and manage an ICD lead defect. Possible therapeutic options are discussed by reviewing the literature.

Do abandoned leads pose risk to implantable cardioverter-defibrillator patients?

BACKGROUND

With the increased number of implantable cardioverter-defibrillator (ICD) recipients and the frequent need for device upgrading, lead malfunction is a concern, but the optimal approach to managing nonfunctioning leads is unknown.

OBJECTIVE

The purpose of this study was to determine the rate and characteristics of complications related to abandoned ICD leads.

METHODS

Patients with abandoned leads were identified by retrospective review of the Mayo Clinic ICD database from August 1993 to May 2002. We reviewed the medical records to assess long-term follow-up for venous thromboembolic complications, device sensing malfunction, appropriateness of delivered shocks, defibrillation threshold (DFT) values before and after lead abandonment, and subsequent surgical procedures related to devices or leads.

RESULTS

We identified 78 ICD patients (81% males; mean age 63 +/- 14 years) with 101 abandoned leads (69 in the right ventricle, 31 in the right atrium or superior vena cava, 1 in the coronary sinus). During a mean follow-up of 3.1 +/- 2.0 years, neither sensing malfunction nor venous thromboembolic complications were detected. DFT values were high in 13 patients (17%), but there was no significant increase in mean DFT values before and after lead abandonment in 43 patients for whom both values were available (16.2 +/- 9.2 J before abandonment vs 14.1 +/- 5.5 J after; P = .24). Fourteen patients (18%) required further ICD-related surgery; none of these operations were attributed to abandoned leads. Five-year rates of appropriate and inappropriate shocks were 25.9% and 20.5%, respectively.

CONCLUSION

Abandoning a nonfunctioning lead appears to be safe and does not pose a clinically significant additional risk of future complications.

Necessity for surgical revision of defibrillator leads implanted long-term: causes and management

BACKGROUND

Defibrillator lead malfunction is a potential long-term complication in patients with an implantable cardioverter-defibrillator (ICD). The aim of this study was to determine the incidence and causes of lead malfunction necessitating surgical revision and to evaluate 2 approaches to treat lead malfunction.

METHODS AND RESULTS

We included 1317 consecutive patients with an ICD implanted at 3 European centers between 1993 and 2004. The types and causes of lead malfunction were recorded. If the integrity of the high-voltage part of the lead could be ascertained, an additional pace/sense lead was implanted. Otherwise, the patients received a new ICD lead. Of the 1317 patients, 38 experienced lead malfunction requiring surgical revision and 315 died during a median follow-up of 6.4 years. At 5 years, the cumulative incidence was 2.5% (95% confidence interval, 1.5 to 3.6). Lead malfunction resulted in inappropriate ICD therapies in 76% of the cases. Implantation of a pace/sense lead was feasible in 63%. Both lead revision strategies were similar with regard to lead malfunction recurrence (P=0.8). However, the cumulative incidence of recurrence was high (20% at 5 years; 95% confidence interval, 1.7 to 37.7).

CONCLUSIONS

ICD lead malfunction necessitating surgical revision becomes a clinically relevant problem in 2.5% of ICD recipients within 5 years. In selected cases, simple implantation of an additional pace/sense lead is feasible. Regardless of the chosen approach, the incidence of recurrent ICD lead-related problems after lead revision is 8-fold higher in this population.

Two Different Therapeutic Strategies in ICD Lead Defects: Additional Combined LeadVersus Replacement of the Lead

OBJECTIVES

Implantation of an additional HV-P/S lead versus extraction of the defective HV-P/S lead and implantation of a new one is one possible therapeutic approach in cases of a defective high-voltage pace/sense lead (HV-P/S). No information is available on potential differences in clinical outcome in these different approaches.

METHODS

Between January 2000 and February 2006, 86 patients with HV-P/S lead defect received either an additional transvenous HV-P/S lead (n = 33, group 1) or the HV-P/S lead was replaced (n = 53, group 2). The duration of the initially implanted leads was significantly different in the two groups (7.4 +/- 2.9; group 1 and 4.1 +/- 3.4 years; group 2). The outcome of these two groups of patients was retrospectively analyzed.

RESULTS

Seventy-three patients [85%] survived until the end of follow-up of 29 +/- 15 (group 1) and 33 +/- 21 (group 2) months (P = ns), respectively. Thirteen patients died: six in group 1 and seven in group 2 (P = ns). Fourteen patients experienced perioperative complications (group 1: six; group 2: eight; P = ns). ICD system-related complications occurred in 22 patients (group 1: seven; group two: 15; P = ns). The event-free cumulative survival of patients with additional and replaced HV-P/S lead for postoperative events (including death) after 1, 2, and 3 years was 82%, 70%, 70%, and 86%, 81%, 66%, respectively (P = 0.93).

CONCLUSIONS

Implantation of an additional HV-P/S lead or replacement of the HV-P/S lead in case of HV-P/S lead failure is statistically not different concerning mortality and morbidity. There are no predictors for further lead defects. Implantation of an additional HV-P/S lead should not be recommended in young patients or patients with greater likelihood of living many years. Predictors for death were an age over 70 years and renal insufficiency.

Annual rate of transvenous defibrillation lead defects in implantable cardioverter-defibrillators over a period of >10 years

BACKGROUND

The number of patients with longer follow-up after implantation of an implantable cardioverter-defibrillator is increasing continuously. Defibrillation lead failure is a typical long-term complication. Therefore, the long-term reliability of implantable cardioverter-defibrillator leads has become an increasing concern. The aim of the present study was to assess the annual rate of transvenous defibrillation lead defects related to follow-up time after lead implantation.

METHODS AND RESULTS

A total of 990 consecutive patients who underwent first implantation of an implantable cardioverter-defibrillator between 1992 and May 2005 were analyzed. Median follow-up time was 934 days (interquartile range, 368 to 1870). Overall, 148 defibrillation leads (15%) failed during the follow-up. The estimated lead survival rates at 5 and 8 years after implantation were 85% and 60%, respectively. The annual failure rate increased progressively with time after implantation and reached 20% in 10-year-old leads (P<0.001). Lead defects affected newer as well as older models. Patients with lead defects were 3 years younger at implantation and more often female. Multiple lead implantation was associated with a trend to a higher rate of defibrillation lead defects (P=0.06). The major lead complications were insulation defects (56%), lead fractures (12%), loss of ventricular capture (11%), abnormal lead impedance (10%), and sensing failure (10%).

CONCLUSIONS

An increasing annual lead failure rate is noted primarily during long-term follow-up and reached 20% in 10-year-old leads. Patients with lead defects are younger and more often female.

Fatal Inappropriate ICD Shock

INTRODUCTION

Inappropriate implantable cardioverter defibrillator (ICD) therapy carries a low but relevant risk of ventricular proarrhythmia. In the present case, the extremely rare event of a fatal arrhythmia caused by inappropriate therapy is reported. Dislodgement of the ventricular lead to the level of the tricuspid annulus led to additional sensing of the atrial signal during sinus tachycardia. Spuriously, ventricular fibrillation was sensed and induced inappropriate ICD shocks. The fourth inappropriate shock caused ventricular fibrillation, which was subsequently undersensed by the dislodged lead due to low ventricular amplitudes. The ICD started antibradycardic pacing during ventricular fibrillation. After initial successful resuscitation, the patient died 1 week later due to severe hypoxic brain damage. Although not preventable in the present case, it underlines the necessity of immediate interrogation of the ICD after ICD therapy and deactivation of the ICD in the setting of a dislodged endocardial lead and intensive care monitoring of the patient until revision.

Inappropriate implantable cardioverter-defibrillator discharges unrelated to supraventricular tachyarrhythmias

AIMS

The development of implantable cardioverter-defibrillators (ICDs) with QRS morphology discrimination and dual-chamber sensing capabilities has improved the differentiation of supraventricular from ventricular tachycardias (VTs). Inappropriate ICD discharges may result from extracardiac signals caused by electromagnetic interference (EMI), because of electric fields and leakage currents from domestic or medical electrical devices, damaged sensing leads, and various cardiac and extracardiac signals that mimic VT and/or ventricular fibrillation. The aim of our study was to determine retrospectively the incidence and clinical relevance of these ICD behaviours and offer possible therapeutic solutions.

METHODS AND RESULTS

We have observed inappropriate discharges unrelated to supraventricular arrhythmias in 13 (3.9%) of the 336 patients implanted with ICDs in our centre from 1989 to 2005. Seven patients received inappropriate shocks following exposure to external EMI: improperly grounded electric stove, electrically powered watering system, hydro-massage bath, electrical pruner, electrocautery current during cardiac surgery, transcutaneous electric nerve stimulation. In four patients, spurious discharges were related to internal noise of the ICD system from inappropriate lead connections. In two cases, erroneous antitachycardia therapy was delivered following different body signals oversensing (T-wave oversensing, wide QRS double-counting and myopotentials). In nine patients, non-invasive solutions prevented further inappropriate therapies (avoidance of EMI, malfunctioning atrial lead exclusion, ventricular sensing reprogramming). In four patients, surgical revision of the system was required (lead connections or position revision).

CONCLUSION

In our experience, inappropriate ICD discharges unrelated to supraventricular arrhythmias occurred in about 4% of ICD patients. A careful evaluation of clinical data and telemetric information (lead impedance, sensed R-wave, stored electrograms) is essential in order to understand the nature of inappropriate ICD discharges and to select the most appropriate solution.

Development and testing of an algorithm to detect implantable cardioverter-defibrillator lead failure

BACKGROUND

Implantable cardioverter-defibrillator (ICD) lead failures often present as inappropriate shock therapy. An algorithm that can reliably discriminate between ventricular tachyarrhythmias and noise due to lead failure may prevent patient discomfort and anxiety and avoid device-induced proarrhythmia by preventing inappropriate ICD shocks.

OBJECTIVES

The goal of this analysis was to test an ICD tachycardia detection algorithm that differentiates noise due to lead failure from ventricular tachyarrhythmias.

METHODS

We tested an algorithm that uses a measure of the ventricular intracardiac electrogram baseline to discriminate the sinus rhythm isoelectric line from the right ventricular coil-can (i.e., far-field) electrogram during oversensing of noise caused by a lead failure. The baseline measure was defined as the product of the sum (mV) and standard deviation (mV) of the voltage samples for a 188-ms window centered on each sensed electrogram. If the minimum baseline measure of the last 12 beats was <0.35 mV-mV, then the detected rhythm was considered noise due to a lead failure. The first ICD-detected episode of lead failure and inappropriate detection from 24 ICD patients with a pace/sense lead failure and all ventricular arrhythmias from 56 ICD patients without a lead failure were selected. The stored data were analyzed to determine the sensitivity and specificity of the algorithm to detect lead failures.

RESULTS

The minimum baseline measure for the 24 lead failure episodes (0.28 +/- 0.34 mV-mV) was smaller than the 135 ventricular tachycardia (40.8 +/- 43.0 mV-mV, P <.0001) and 55 ventricular fibrillation episodes (19.1 +/- 22.8 mV-mV, P <.05). A minimum baseline <0.35 mV-mV threshold had a sensitivity of 83% (20/24) with a 100% (190/190) specificity.

CONCLUSION

A baseline measure of the far-field electrogram had a high sensitivity and specificity to detect lead failure noise compared with ventricular tachycardia or fibrillation.

Safety of Sports Participation in Patients with Implantable Cardioverter Defibrillators: A Survey of Heart Rhythm Society Members

Safety of Sports for ICD Patients.

INTRODUCTION

The safety of sports participation for patients with implantable cardioverter defibrillators (ICDs) is unknown, and recommendations among physicians may vary widely. The purposes of this study were to determine current practice among patients with ICDs and their physicians regarding sports participation, and to determine how many physicians have cared for patients who have sustained adverse events during sports participation.

METHODS AND RESULTS

A survey was mailed to all 1,687 U.S. physician members of the Heart Rhythm Society. Among 614 respondent physicians, recommendations varied widely. Only 10% recommended avoidance of all sports more vigorous than golf. Seventy-six percent recommended avoidance of contact, and 45% recommend avoidance of competitive sports. Most (71%) based restrictions on patients' underlying heart disease. Regardless of recommendations, most physicians (71%) reported caring for patients who participated in sports, including many citing vigorous, competitive sports, most commonly cited were basketball, running, and skiing. ICD shocks during sports were common, cited by 40% of physicians. However, few adverse consequences were reported. One percent of physicians reported known injury to patient (all but 3 minor); 5%, injury to the ICD system, and <1%, failure of shocks to terminate arrhythmia. The most common adverse event reported was lead damage attributed to repetitive-motion activities, most commonly weightlifting and golf.

CONCLUSIONS

Physician recommendations for sports participation for patients with ICDs varies widely. Many patients with ICDs do participate in vigorous and even competitive sports. While shocks were common, significant adverse events were rare.

Automatic Identification of Clinical Lead Dysfunctions

Implantable cardioverter defibrillators (ICD) lead dysfunctions can cause inappropriate shocks. Current ICDs store lead diagnostics and detected episodes. This stored information with intracardiac electrograms (EGM) and sensed RR interval patterns may characterize the ICD lead performance. The aim of this analysis was to determine the sensitivity and positive predictive value (PPV) of an automatic lead dysfunction identification algorithm. This algorithm uses RR and EGM data to distinguish noncardiac oversensing (OS), for example, due to conductor fracture, and cardiac OS, for example, T-wave OS, from detected episodes. The algorithm also uses lead diagnostics: sensing integrity counter trends (e.g., RR intervals <140 ms), nonsustained tachyarrhythmias episodes with a mean RR <200 ms and impedance trends to identify lead fractures. The PPV was determined using the stored memory from 1,756 ICD patients enrolled in a 13-center long-term lead study with an average follow-up of 18.3 patient-months. Sensitivity was determined in 35 patients who presented with OS or lead fracture-related adverse events confirmed by stored ICD diagnostics. The algorithm sensitivity was 97.1% (34/35). There were 43 additional patients identified by the algorithm without an adverse event. Stored ICD diagnostics confirmed lead dysfunctions in 32 of 43 patients corresponding with an 85.7% PPV (66/77). ICD memory diagnostics and episodes with intracardiac EGM may be used to identify ICD lead dysfunctions with high sensitivity and PPV. This algorithm may be implemented in postprocessing ICD environments (e.g., remote server, programmer) to rapidly identify lead dysfunction prior its clinical manifestation.

Inappropriate Discharges of Intravenous Implantable Cardioverter Defibrillators Owing to Lead Failure

We describe here the case of a 58-year-old female patient who experienced inappropriate shocks from her implantable cardioverter-defibrillator (ICD). Stored electrograms from her ICD showed high frequency noise preceding the shock. Although the pacing threshold was normal and lead fracture was not found in chest X-rays, pacing lead impedance decreased to 480 omega. Moreover, such high frequency noise was observed by electrogram telemetry, but not by routine evaluation every 3 months. ICD lead dysfunction was suspected, so we elected to replace the ICD lead system. At the time of the operation, lead impedance was 410 omega and pacing threshold was the same as it was at the time of the ICD implantation, and no lead insulation disturbances were observed in the generator pocket. However, manipulation of the lead system produced high frequency noise reproducibly. Since some of the ICD lead dysfunction initially was clinically silent at rest, dysfunction was difficult to detect before serious problems occurred. Therefore, more careful evaluation of the ICD lead system is needed during long-term follow-up of ICD implants.

An algorithm to predict implantable cardioverter-defibrillator lead failure

OBJECTIVES

The goal of this analysis was to test an algorithm that identifies implantable cardioverter-defibrillator (ICD) lead problems before clinical failure and/or inappropriate therapy.

BACKGROUND

The ICD lead failures typically present as inappropriate shock therapy. Identifying lead failures before their clinical presentation may prevent patient discomfort, improve device longevity, and avoid device-induced proarrhythmia.

METHODS

We tested an algorithm that uses two measures of oversensing and one measure of abnormal impedance to detect a lead failure. The oversensing measures consisted of a counter for RR intervals <140 ms and nonsustained ventricular tachycardia episodes with mean RR interval <200 ms. The impedance measure tracked lead impedances every day and each week. Abnormal impedance was defined as a decrease in impedances or an outlier value compared with baseline. Lead failures were identified when both oversensing measures were met or abnormal impedance and one oversensing measure occurred. The stored data from 696 patients with an ICD were analyzed to determine the sensitivity and specificity of the algorithm to detect lead failures.

RESULTS

Twenty-nine patients demonstrated clinical lead failures with an average of 6 +/- 9 inappropriate shocks per patient. The two oversensing measures used in the algorithm predicted 72% (21 of 29) of the lead failures. Fulfilling at least two of the three impedance and oversensing measures, the sensitivity of our algorithm was 83% (24 of 29) with a 100% (667 of 667) specificity.

CONCLUSION

Oversensing combined with abnormal impedance trends may be used to identify ICD lead failures with high sensitivity and very high specificity.

Death Due to an Implantable Cardioverter Defibrillator

Inappropriate therapy due to noise oversensing caused a true ventricular fibrillation (VF) and death of a patient. A 49-year-old patient with a history of dilated cardiomyopathy received a double-chamber implantable cardioverter defibrillator (ICD) in 1991 for a sustained inducible ventricular tachycardia (VT). One appropriate shock delivered in 1994 terminated an episode of VT. The generator was replaced in 1995 and in 2000, and was connected to the initial leads. Three months after the second replacement, the patient received six consecutive shocks related to detection of noise interpreted as VF. Unfortunately, the sixth shock triggered a true VF, which was not treated due to end of the therapeutic sequence, and the patient died. The causes of the dysfunction are discussed.

Durability of Repaired Sensing Leads Equivalent to that of New Leads in Implantable Cardioverter Defibrillator Patients with Sensing Abnormalities

Breaks in the insulation portions of implantable cardioverter defibrillator (ICD) leads may cause nonphysiological sensing and subsequent inappropriate ICD therapy, and may also interfere with the sensing and pacing functions of the ICD. Previously, leads with insulation breaks have been replaced with new sensing leads. However, repair of leads, utilizing a commercially available patch kit may reduce the morbidity, hospital stay, and cost of lead replacement. The long-term durability of these repairs has not previously been reported and is the subject of this study. Patients undergoing ICD sensing lead repair or replacement constituted the study population. Patients were followed at 3 month intervals with an endpoint of new lead abnormalities necessitating repeat lead repair or replacement. Twenty-five patients underwent lead repair and 27 individuals underwent lead replacement for either preoperative nonphysiological sensing (n = 25) or intraoperative evidence of insulation break (n = 27). There was no significant difference between the individuals undergoing lead repair or replacement in age (59 +/- 9 vs 60 +/- 12 years), mean left ventricular ejection fraction (40%+/- 18% vs 33%+/- 17%) or age of the lead being repaired or replaced (4.5 +/- 2.0 years vs 5.0 +/- 2.0 years). During follow-up of 44 +/- 23 months, 4 of the repaired leads and 4 of the replaced leads developed new insulation breaks requiring surgical intervention (P = 0.43). In conclusion, in nearly 4 years of follow-up of patients with sensing lead insulation breaks, there was no difference is subsequent lead survival in those with lead repair compared to those with new sensing leads inserted. The strategy of lead repair, when technically feasible, should thus be considered in all patients with sensing abnormalities secondary to insulation breaks.

Detection and management of an implantable cardioverter defibrillator lead failure: incidence and clinical implications

OBJECTIVES

This study evaluated the long-term reliability of an implantable cardioverter defibrillator (ICD) lead to determine the incidence, clinical presentation, and management of lead failure.

BACKGROUND

Despite recent advances in ICD technology, the long-term reliability of ICD leads remains a significant problem.

METHODS

Concern about long-term reliability of coaxial polyurethane ICD leads caused us to systematically study all patients implanted with Medtronic (Minneapolis, Minnesota) 6936 lead at our institution. We performed follow-up of 74 patients with 76 ICD leads that were implanted from February 28, 1995 to September 8, 1997. Thirty-seven patients underwent routine clinical ICD follow-up testing and ventricular fibrillation induction to determine the status of their ICD lead after a mean follow-up of 68.6 +/- 8.2 months.

RESULTS

The lead survival analysis shows a cumulative failure probability of 37% (confidence interval, 24% to 54%) at 68.6 months. Six patients demonstrated a previously undescribed mode of ICD lead failure: prolonged oversensing immediately after shock therapy. The use of short interval counters to monitor nonphysiologic R-R intervals and the measurement of ring-to-coil impedance detected early lead failures in five patients.

CONCLUSIONS

This analysis shows: 1) problems with ICD leads may not become apparent until late during follow-up and may become a significant late problem, 2) a "signature" mode of lead failure for the 6936 consisting of oversensing of electrical noise following shocks, 3) early detection of lead failure with a short interval counter algorithm or measurement of ring-to-coil impedance may be clinically useful.

Subthreshold test pulses versus low energy shock delivery to estimate high energy lead impedance in implanted cardioverter defibrillator patients

The high energy lead impedance is valuable for detecting lead failure in ICDs, but until recently shock delivery was necessary for high energy impedance measurement. This study compared the use of subthreshold test pulses and low energy test shocks to estimate the high energy impedance. Immediately after implantation of Ventak Prizm ICDs in 29 patients, the lead impedance was measured with five subthreshold (0.4 microJ) test pulses, 5 low energy (1.1 J) shocks, and two to three high energy (16 +/- 4.5 J) shocks. The mean impedances measured using high energy shocks, low energy shocks, and subthreshold pulses were 42.0 +/- 7.3 omega, 46.5 +/- 8.1 omega, and 42.4 +/- 7.1 omega, respectively. The impedances measured using high and low energy shocks differed significantly (P < 0.0001), while those obtained by high energy shocks and low energy pulses did not (P = 0.63). According to the Pearson correlation coefficient, the impedance measurements with subthreshold pulses and low energy shocks were both closely correlated (P < 0.0001) with impedance values determined with high energy shocks. However, while the impedance values tended to be higher when measured with low energy shocks, the concordance correlation coefficient (c) was higher for subthreshold test pulse versus high energy shock (c = 0.92) than for low versus high energy shock (c = 0.73). Furthermore, the intraindividual variability of impedance measurements was lower with subthreshold pulse measurements than with low energy shocks. Compared with low energy shocks, impedance measurement with subthreshold pulses has higher reproducibility and a higher correlation with the impedance obtained by high energy shock delivery. Safe and painless high energy impedance estimation with subthreshold pulses might, therefore, help to detect ICD lead failure during routine follow-up.

The implantable cardioverter defibrillator

Implantable cardioverter defibrillators (ICDs) have evolved from the treatment of last resort to the gold standard therapy for patients at high risk for ventricular tachyarrhythmias. High-risk patients include those who have survived life-threatening arrhythmias, and individuals with cardiac diseases who are at risk for such arrhythmias, but are symptomless. Use of an ICD will affect the patient's quality of life. Some drugs can substantially affect defibrillator function and efficacy, and possible drug-device interactions should be considered. Patients with ICDs may encounter cell phones, antitheft detectors, and many other sources of potential electromagnetic Interference. In addition to treating ventricular tachyarrhythmias, new defibrillators provide full featured dual chamber pacing, and could treat atrial arrhythmias, and congestive heart failure by means of biventricular pacing.