Exploding Implantable Cardioverter Defibrillator

A 79-year-old man with a pectoral implantable cardioverter defibrillator (ICD) system underwent periodic defibrillation threshold testing 18 months after implant. Attempted delivery of a 15-J shock caused a light flash above the pocket and a loud "pop." High-voltage lead impedance was <20 ohms. Pocket exploration revealed insulation abrasion of the high-voltage portion of the single-coil right ventricular lead. The outer shield of the active can pulse was perforated and scorched due to arcing. Device analysis confirmed a shorted transistor in the high-voltage output circuit. Unsuspected physical contact between high-voltage electrodes of opposite polarity within the pocket can cause catastrophic ICD system failure.     

Runaway Pacemaker in an Implantable Cardioverter Defibrillator

Runaway Pacemaker in an ICD. Introduction : Runaway pacemaker is a potentially catastrophic complication of any permanent pacing system.
Methods and Results : A 70-year-old man was found to have erratic behavior of his implantable cardioverter defibrillator (ICD) during a routine outpatient interrogation. His device was turned off, and he was hospitalized in preparation for a pulse generator replacement. During his hospitalization, his ICD unexpectedly began pacing rapidly. Despite prompt resuscitation attempts, the patient died. Postmortem examination of the device demonstrated a crystal oscillator failure.
Conclusion : A previously unrecognized component malfunction is a potentially lethal complication of ICDs.     

Geographic Differences in Implantable Cardioverter Defibrillator Usage

Geographic Differences in ICD Usage. Despite the demonstrated efficacy of implantable cardioverter defibrillators (ICDs) in reducing sudden and total mortality in selected patients, their implantation rates vary greatly among countries. In the United States, the implantation rate is 185 implants per million inhabitants compared with only 31 implants per million in western Europe. The differences in ICD use may be explained by the following factors: manner in which sudden cardiac death is perceived by politicians and physicians (sudden cardiac death is perceived as a “nice way of dying”); differences in indications; physicians' information; prevalence of coronary artery disease; sudden cardiac death survival rates; perceived reliability of alternative treatment (namely, antiarrhythmics including amiodarone); economic backgrounds; and health care politics. Furthermore, the cost of this treatment strategy must be considered. This issue has been raised because generalization of ICD use in patients matching clinical characteristics of patients enrolled in the primary prevention trials may represent a significant economic burden to be added to the already overloaded health care system. This low acceptance may not be entirely related to budget constraint but also to the perceived efficacy of ICDs by physicians and health authorities.     

Implantable Cardioverter Defibrillator Patch Erosion Presenting as Hemoptysis

ICD Patch Erosion. Although the internal cardioverter defibrillator has prevented many premature deaths from lethal ventricular arrhythmias, some complications have occurred with its use. We present a patient who developed a fistula between the left ventricle and a bronchus, caused by erosion of the ventricular patch. The patient's presenting symptom was hemoptysis. Physicians caring for patients with these devices should be aware of this potential problem.     

Implantable Cardioverter Defibrillator Therapy for Life-Threatening Arrhythmias in Young Patients

Objectives: This study examined the indications, efficacy and outcomes of implantable cardioverter defibrillator (ICD) use in the pediatric population. Background: ICDs are first-line therapy for adults resuscitated from sudden cardiac death (SCD) or at high risk for life-threatening ventricular arrhythmias. Use of ICDs in children and young adults is infrequent and there are few data regarding this group. Methods: We abstracted and analyzed data for all patients in whom ICDs were implanted. Results: A total of 38 devices were implanted in 27 patients. Age ranged from 6 to 26 years (mean, 14) and weight ranged from 16 to 124 kg (mean, 47). Diagnoses included long QT syndrome (9), hypertrophic cardiomyopathy [6], repaired congenital heart disease [5];, and idiopathic ventricular tachycardia/fibrillation [4]. Indications comprised resuscitated SCD [15], syncope [9], and life-threatening ventricular arrhythmia [3]. Initial device placement was infraclavicular in 13, abdominal in 13 and intrathoracic in 1. Epicardial leads were used with 5 systems. A single coil lead was used in 17. Seven patients, all previously resuscitated from SCD, experienced 88 appropriate successful discharges. There were 6 inappropriate discharges in 3 patients. Mean time to device replacement was 3.1 years (n = 11). Complications included 2 infected systems, 2 lead dislodgments, 2 lead fractures, 1 post-pericardiotomy syndrome, 1 adverse event with defibrillation threshold (DFT); testing, and 1 patient with psychiatric sequelae. No deaths occurred with implanted ICDs. Conclusions: These data demonstrate that ICDs provide safe and effective therapy in young patients. The indications for ICDs as primary preventive therapy remain uncertain.     

Reproducibility of Ventricular Fibrillation Characteristics in Patients Undergoing Implantable Cardioverter Defibrillator Implantation

Reproducibility of VF Characteristics. Introduction: The purpose of this study was to evaluate the immediate reproducibility of local electrogram characteristics recorded during repeated episodes of induced ventricular fibrillation (VF) in patients undergoing implantable cardioverter defibrillator (ICD) implantation.
Methods and Results: Power spectral analysis (using a fast Fourier transform algorithm) of electrograms recorded during 3 seconds of VF were analyzed in 24 patients undergoing ICD implantation using a Medtronic Transvene lead. Patients had 2 to 7 episodes of VF that were induced during defibrillation threshold testing. VF was induced by burst pacing (n = 20) or T wave shock (n = 4). Simultaneous electrograms during VF were recorded from a Medtronic Transvene lead with the following configurations: (1) a narrow spaced (12 mm) dedicated bipole used clinically for sensing; (2) a unipolar electrogram from the right ventricular coil; and (3) a widely spaced (18.3 mm) integrated bipole using the distal tip and the coil. Intraclass correlation coefficients (ICCs) were determined to examine the reproducibility of these VF characteristics among VF episodes in each patient. Recordings from both bipolar configurations had ICCs from 0.40 to 0.55, whereas unipolar recordings ICCs were below 0.40. Reproducibility was similar for dedicated and integrated recordings.
Conclusions: Frequency characteristics of repeated episodes of VF induced in the same subjects show fair-to-good but not excellent reproducibility. Bipolar recordings were far more reproducible than unipolar recordings, but both bipolar configurations had similar reproducibility. These findings have implications for both the pathophysiology of induced VF and the design of VF detection algorithms.     

Software Error Resulting in Malfunction of an Implantable Cardioverter Defibrillator

Loss of ventricular output resulting from an unexpected software error in a dual chamber implantable cardioverter defibrillator (ICD) is reported. A 70-year-old man with a dual chamber ICD implanted for a history of cardiac arrest and infra-Hisian block presented with acute onset of dizziness. He was found to have loss of ventricular output due to an internal software problem. The problem was corrected by software reprogramming via the programmer. This malfunction exemplifies the potential ability to correct current-generation ICD software problems noninvasively, thus avoiding the need for replacement.     

Myopotential Sensing by a Dual Chamber Implantable Cardioverter Defibrillator:

Myopotential Oversensing by a Dual Chamber ICD. Introduction : Inappropriate discharges and/or improper inhibition of bradycardia pacing due to oversensing of extraneous signals in implantable cardioverter defibrillators (ICDs) have been described. With one exception, no previous report involving an intact lead system bas cited myopotential oversensing as the cause.
Methods and Results : Two case reports of myopotential oversensing by a dual chamber ICD system are reported. In the first patient suffering from chronic pulmonary obstructive disease, intermittent myopotential seasing during labored respiration resulted in episodic inhibition of bradycardia pacing. In the second patient, oversensing of sustained myopotentials generated during strenuous isometric activity resulted in an inappropriate ICD discharge. For both, the ICD system consisted of a CPI model 1810 Ventak AV used in conjunction with a model 0125 Endotak lead, incorporating integrated bipolar sensing.
Conclusion : Although modern ICDs have proven to be highly effective in detecting and terminating malignant tachyarrhythmias, the opportunity for improving their detection specificity remains.     

Cost‐Effectiveness of Implantable Cardioverter Defibrillator Therapy

ICD Cost‐Effectiveness. Cost‐efficacy assessment of implantable cardioverter defibrillator (ICD) therapy has proved contentious and may have limited uptake of ICD therapy, particularly in Europe. Published modeling assessments are too inaccurate to determine clinical practice, and assessments based on clinical studies are incomplete (from the cost‐efficacy viewpoint). Although ICD therapy seems certain to be most cost‐effective in patients who are likely to have good longevity if their risk of sudden cardiac death is countered, the benefit of ICD therapy is not necessarily limited to such groups. Physicians and health economists need to develop a better understanding of how to assess high‐technology therapy costs so that uptake of such therapy is appropriately expedited with due regard to ethical and cost constraints.     

Predictive Value of QT Dispersion for Ventricular Tachyarrhythmias in Patients with Implantable Cardioverter Defibrillator

Background: QT dispersion, measured as interlead variability of QT intervals in the surface electrocardiogram, has been demonstrated to provide an indirect measurement of the inhomogeneity of myocardial repolarization as a potential substrate for ventricular arrhythmias. Methods: QT dispersion was measured in the standard 12-lead ECG in 51 patients at the time of implantation of a third generation implantable cardioverter defibrillator (ICD) with automatic electrogram storage capability for electrical events triggering device therapy. In addition, QT dispersion was measured in 100 age- and sex-matched healthy controls. All 5 1 study patients with ICD were prospectively followed to determine possible associations between QT dispersion at implant and subsequent spontaneous ICD shocks for ventricular tachyarrhythmias (VT). Results: Rate-corrected QT dispersion and adjusted QTc dispersion, which takes account of the number of leads measured, were significantly greater in ICD patients compared to controls (76 ± 25 ms vs 46 ± 11 ms, and 24 ± 7 ms vs 14 ± 3 ms respectively, P < 0.0 1). During 15 ± 8 months follow-up, ventricular tachyarrhythmias occurred in 23 (45%) of 51 ICD patients. QTc dispersion and adjusted QTc dispersion were not significantly different between ICD patients with ventricular tachyarrhythmias and ICD patients without ventricular tachyarrhythmias during follow-up (74 ± 19 ms versus 77 ± 29 ms, and 23 ± 6 ms vs 25 ± 8 ms respectively). Conclusion: Increased QT dispersion measured in the 12-lead standard ECG does not appear to be a useful marker for future arrhythmic events in a mixed patient population with ICD.     

Role of Amiodarone in the Era of the Implantable Cardioverter Defibrillator

Amiodarone is one of the most frequently used antiarrhythmic drugs in clinical practice. In patients with atrial fibrillation, in whom rhythm control is judged desirable, amiodarone is the most effective therapy. Amiodarone effectively prevents atrial fibrillation and may improve quality of life, but there is no evidence that it decreases mortality or severe morbidity in atrial fibrillation. In patients at risk for life-threatening ventricular arrhythmias, amiodarone may decrease mortality to a small degree, but the evidence for this benefit is incomplete. Patients with implantable cardioverter defibrillators frequently require antiarrhythmic drug therapy, especially to treat electrical storm. Amiodarone is useful in these patients; however, it may increase defibrillation thresholds in some patients. In patients with out-of-hospital DC shock-resistant VF, amiodarone is the most effective antiarrhythmic drug available to assist in resuscitation. Amiodarone is a complicated drug, and its optimal use requires careful patient surveillance with respect to potential adverse effects. (J Cardiovasc Electrophysiol, Vol. 14, pp. S78-S81, September 2003, Suppl.)     

Body Surface Potentials During Discharge of the Implantable Cardioverter Defibrillator

Body Surface Potentials During ICD Discharge. Introduction: Little is known about the hazard for persons in contact with patients experiencing a high-voltage discharge of their implantable cardioverter defibrillator (ICD). Compared to epicardial systems, this risk may be increased with transvenous electrode systems and particularly in active can configurations. Methods and Results: In 23 patients with a transvenous active can ICD system, body surface potentials V_S and current through an external resistance were measured during 35 discharges. V_S was detected using skin electrodes positioned over the left subpectorally implanted pulse generator [C], apex of the heart [A], and the right pectoral region [RP]. Mean V_S during discharges without an external shunt resistance ranged between 13 and 63.8 V [C to A] and 12.5 to 47.3 V [C to RP] (ICD peak stored/output voltage V_cap= 183 to 606 V, n = 20). Mean current flow [C to A] was 8.2 to 46.8 mA (V_cap= 288 to 633 V. n = 10) and 42 to 120.7 mA (V_cap= 447 to 579 V, n = 5) across a resistance of 1.696 and 797 ω, respectively. Conclusion: During high-output shocks, a considerable potential difference is present on the hody surface of ICD patients that, according to the literature, may induce a single cardiac response in a bystander. Analogous to spontaneous extrasystoles, there is only a minimal chance of triggering a tachyarrhythmia by this stimulated extra beat. Direct induction of ventricular fibrillation is unlikely, since reported fibrillation threshold values are much higher than the ohserved magnitudes of current and voltage.     

Cost-Effectiveness of the Implantable Cardioverter Defibrillator

Many clinicians and policymakers are concerned whether use of the implantable defibrillator (ICD) is justified in view of its high cost. Three randomized trials of the ICD have reported economic outcomes. Each trial found a large difference in cost between patients assigned to an ICD versus patients assigned to conventional therapy that persisted over three to six years of follow-up. Each trial also found better survival among ICD patients, and calculated ICD cost-effectiveness (CE) ratios between 27,000 dollars per life year added and 139,000 dollars per life year added. The variability in the cost-effectiveness ratios among trials is mainly due to variability in the years of life added by the ICD among the trials and, by extension, among patient subgroups. A rough rule of thumb is that the ICD will be economically attractive when it prolongs mean survival by six months or more, which is attainable in higher risk patient subgroups.     

Sudden Death in Recipients of Transvenous Implantable Cardioverter Defibrillator Systems:

INTRODUCTION: Transvenous implantable cardioverter defibrillator (ICD) systems are very effective in preventing sudden death; however, little is known about terminal events and potential causes and mechanisms of sudden death in recipients of these devices. METHODS AND RESULTS: We analyzed 74 cases of sudden death among patients enrolled in several clinical investigations of transvenous ICD systems. Eighty-one percent were men (mean age 68+/-10 years), 86% had coronary artery disease, mean left ventricular ejection fraction was 0.27+/-0.11, and two thirds presented with sustained ventricular tachycardia. The final event was witnessed in 65 patients (81%). Based on reported ICD shocks, documented rhythm, and/or postmortem device data, sudden death was deemed tachyarrhythmic in 49 cases (66%), nontachyarrhythmic in 12 (16%), and indeterminate in the remaining 13 (18%). Multivariate analysis of several clinical and nonclinical factors found advanced age (> 65 years, P = 0.03, odds ratio [OR] 1.75, 95 % confidence interval [CI] 1.05 to 2.92), reduced left ventricular ejection fraction (< 0.35, P < 0.01, OR 3.51, CI 1.66 to 7.40), and having antibradycardia pacing ICDs (P = 0.02, OR 5.26, CI 1.37 to 20.0) to be independent predictors of sudden death. One or more predisposing factors and/or potential causes of sudden death were identified in 21 patients (28%). CONCLUSION: In this select group of transvenous ICD recipients, (1) sudden death was associated with ventricular tachycardia/ventricular fibrillation in at least two thirds of cases, (2) nearly one third of patients had one or more factors, some device related, that could have been associated with sudden death, and (3) death ensued despite appropriate ICD therapies and, in many cases, external resuscitation, suggesting acute adverse events as common terminal factors.     

Effects of Procainamide and Lidocaine on Defibrillation Energy Requirements in Patients Receiving Implantable Cardioverter Defibrillator Devices

Effects of Procainamide and Lidocaine on Defibrillation. intntduction: In acute canine studies, lidocaine. but not prucainamidc, increases defibrillation energy requirements. We evaluated the effects of lidocaine or procainamide on defihrillation energy requirements in 27 patients undergoing intraoperative testing fur implantable cardioverter dcfibrillator device placement.
Methods and Results: Patients were tested off antiarrhythmic drugs and again following either lidocaine (200 to 250 mg loading and 3 mg/min maintenance infusions) or procainamide (1 gm loading and 3 to 4 mg/min maintenance infusions). The defibrillation testing protocol consisted of initial testing at 15 J, followed by higher or lower energies to determine the lowest energy producing three consecutive successful defibrillations. Overall, the mean defibrillation energy increased from 14 ± 5 J to 18 ± 7 J during lidocaine (plasma concentration 5.1 ± 1.6 μ/mL; P < 0.02) but were similar at baseline (12 ± 5 J) and during procainamide infusion (13 ± 6 J) (plasma concentration: procainamide 10.7 ± 7.2 μ/rnl.; N-acetyl procainamide 1.0 ± 0.4 μ/niL). A positive linear correlation was found between lidocaine plasma concentration and percent change in defibrillation energy (lidocaine: r = 0.61; P = 0.01). Procainamide raised the defibrillation energy in three patients, two with supra therapeutic plasma concentrations. The increase in defibrillation energy equaled or exceeded 25 J in four patients after lidocaine and in one patient after procainamide.
Conclusion: The data suggest that at high plasma concentrations, lidocaine and procainamide adversely affect defibrillation energy requirements consistent with an adverse, concentration-dependent effect of sodium channel blockade on defibrillation energy requirements in patients.     

Implantable Cardioverter Defibrillators in Patients with Valvular Cardiomyopathy

Sudden Death Prevention in Valvular Cardiomyopathy. Background: Implantable cardioverter‐defibrillators (ICDs) are beneficial for preventing sudden cardiac death (SCD) in patients with previous SCD or left ventricular dysfunction. Objective: The objective was to investigate the outcomes of ICD implantation in patients who have surgery for valvular cardiomyopathy (VCM). Methods: We identified patients with VCM who had ICD implantation after valve surgery. Age‐ and sex‐matched patients who received an ICD for ischemic cardiomyopathy (ICM) and dilated cardiomyopathy (DCM) served as controls. Patients with VCM who had valve surgery but did not receive an ICD served as an additional control group. We compared mortality and appropriate ICD discharges between the study group and control groups. Results: Mean (SD) age (31 patients with VCM with ICD, 30 with ICM, 26 with DCM, and 62 patients with VCM without ICD) was 60 (15) years, 73% were men. Ejection fraction at ICD implantation was 34%, 26%, and 23% for the VCM with ICD, ICM, and DCM groups, respectively (P = 0.03). After a median follow‐up of 4.1 years, survival was not significantly different among ICD groups (P = 0.06). The annual appropriate shock rate was 5%, 10%, and 4% for the VCM with ICD, ICM, and DCM groups, respectively (P = 0.71). Compared to VCM without ICD, patients with VCM and ICD had comparable survival (P = 0.82) despite a reduced LVEF following valve surgery. Conclusion: Patients with VCM who undergo ICD implantation for SCD prevention have similar appropriate ICD discharge rates and mortality as do those with ICM and DCM. These data are hypothesis generating and deserve confirmation with large‐scale prospective studies. (J Cardiovasc Electrophysiol, Vol. 23, pp. 1326‐1332, December 2012)     

Clinical Experience with a Dual-Chamber Implantable Cardioverter Defibrillator to Treat Atrial Tachyarrhythmias

INTRODUCTION: This study evaluated the safety and efficacy of a new dual-chamber implantable cardioverter defibrillator (ICD) to detect and treat atrial tachyarrhythmias in patients with drug-refractory atrial fibrillation (AF) and no indication for a ventricular ICD. METHODS AND RESULTS: A dual-chamber ICD (Medtronic 7250 Jewel AF) was implanted in 144 of 146 patients. The device discriminates atrial tachycardia from AF based on cycle length and regularity, and uses atrial overdrive pacing as well as shocks to terminate tachyarrhythmia episodes. Patients were followed for an average of 12.6+/-6.2 months. Use of antiarrhythmic drugs was 63% at baseline and did not change over time. Kaplan-Meier estimates of 12-month complication-free survival, device therapy survival, and patient survival were 85%, 91%, and 98%, respectively. Positive predictive accuracy of spontaneous atrial tachyarrhythmia detection was 99%, while atrial overdrive pacing and shocks terminated 40% and 87% of treated episodes, respectively. Median duration of successfully treated episodes was 8.9 minutes versus 144 minutes for the therapy failures. There was no reduction in the use of patient-activated shock therapy over time; at the 12-month follow-up evaluation, 94% of patients were in sinus rhythm. Ventricular tachyarrhythmias (67 episodes) were detected and appropriately treated in 7.6% of patients. CONCLUSION: This dual-chamber ICD appears to be safe and well tolerated in patients with drug-refractory symptomatic atrial tachyarrhythmias. The device, used in combination with drugs, effectively treats atrial tachyarrhythmias with pacing and/or shock therapies and decreases the median episode duration. In addition, the device protects from ventricular tachyarrhythmias in patients with AF and structural heart disease.