Complications of third-generation implantable cardioverter defibrillator therapy

Clinical outcomes of subcutaneous implantable cardiac defibrillator implantation - Iran SICD registry

BACKGROUND

The subcutaneous implantable-defibrillator (S-ICD) is a relatively new alternative to the transvenous ICD system to minimize intravascular lead-related complications. This paper presents outcome of SICD implantation in patients enrolled in Iran S-ICD registry.

METHODS

Between October 2015 and June 2022, this prospective multicenter national registry included 223 patients with a standard indication for an ICD, who neither required bradycardia pacing nor needed cardiac resynchronization to evaluate the early post-implant complications and long-term follow-up results of the S-ICD system.

RESULTS

The mean age of the patients was 45 ± 17 years. The majority (79.4%) were male. Ischemic cardiomyopathy (39.5%) was the most common underlying disorder among patients selected for S-ICD implant. Most study patients (68.6%) had ICD for primary prevention of sudden cardiac death. Seven patients (3.1%) were found to have suboptimal lead positions. Six patients (2.7%) developed a pocket hematoma; all were managed medically. During a mean follow-up of 2 years, the appropriate therapy was recorded in 13% of the patients and inappropriate ICD intervention mainly due to supraventricular tachycardia in 8.9%. Pocket infection was observed in four patients (1.8%) and five patients (2.2%) died mainly due to heart failure.

CONCLUSION

S-ICDs were effective at detecting and treating both induced and spontaneous ventricular arrhythmias. Major clinical complications were rare.

A Shocking Case of Far-Field Atrial Oversensing in Giant-Cell Myocarditis

We report a unique case of delivery of inappropriate implantable cardioverter-defibrillator therapies related to a “perfect storm”: presence of an integrated lead, insufficient lead slack related to right heart dilation resulting in shock coil misplacement, myocarditis with loss of R waves, and the concomitant occurrence of an incessant atrial tachycardia. (Level of Difficulty: Advanced.)

First clinical experience of the safety and feasibility of total subcutaneous implantable defibrillator in an Asian population

AIMS

The safety and feasibility of a subcutaneous implantable cardioverter-defibrillator (S-ICD) has been demonstrated in the treatment of life-threatening ventricular tachyarrhythmias (VT). Nonetheless, its safety and feasibility in an Asian population with smaller body-build is unclear.

METHODS AND RESULTS

Twenty-one Asian patients who underwent S-ICD from 1 April 2014 to 2 February 2015 in five institutions in Hong Kong and Singapore were retrospectively reviewed. Twenty-one patients with a mean age of 50.0 ± 14.1 years (range 29-77 years, 82.6% male) were included. Among them, 17 (81.0%) were Chinese, 3 (14.3%) were Malay, and 1 (4.8%) was Indian. Their mean body mass index was 23.0 ± 4.0 kg/m(2). An S-ICD was implanted for primary and secondary prevention in 13 (61.9%) and 8 (38.1%) patients, respectively. The indications included Brugada syndrome (n = 6, 28.6%), ischaemic cardiomyopathy (CMP, n = 6, 28.6%), dilated CMP (n = 4, 19.0%), hypertrophic CMP (n = 2, 9.5%), and idiopathic ventricular fibrillation (n = 2, 9.5%). Three patients (14.3%) had prior infected transvenous ICD. There were no acute complications but eight wound complications (persistent wound bleeding requiring intervention = 2; delayed wound healing: upper sternal wound = 3; generator site = 1; local wound infection = 2) were observed in six (28.2%) patients. After a mean follow-up of 107.2 ± 81.3 days (range of 14-254 days), one patient underwent three successful appropriate shocks for treatment of VTs. No inappropriate therapy was documented.

CONCLUSION

Our initial experience shows that S-ICD is a feasible treatment for VT among an Asian population with smaller body-build. There was nonetheless a relatively high rate of wound complications.

Subcutaneous implantable cardioverter-defibrillator: Initial experience

BACKGROUND

Implantable cardioverter-defibrillators (ICDs) are important tools in the prevention of sudden death, but implantation requires transvenous access, which is associated with complications. Subcutaneous implantable cardioverter-defibrillators (S-ICDs) may prevent some of these complications.

AIM

To evaluate the therapeutics and complications associated with S-ICD systems.

METHODS

S-ICD implantation was planned in 23 patients, for whom the indications were vascular access problems, increased risk of infection or young patients with long predicted follow-up. The population consisted of four patients with ischemic heart disease, three of them on hemodialysis (two with subclavian vein thrombosis), five with left ventricular noncompaction, four with Brugada syndrome, three with arrhythmogenic right ventricular cardiomyopathy, one with transposition of the great vessels, two with dilated cardiomyopathy and four with hypertrophic cardiomyopathy.

RESULTS

S-ICDs were implanted in 21 patients, two having failed to fulfil the initial screening criteria. Mean implantation time was 77 minutes, with no complications. Defibrillation tests were performed, and in one patient the generator had to be repositioned to obtain an acceptable threshold. In a mean follow-up of 14 months, 10 patients had S-ICD shocks, which were appropriate in half of them; one developed infection, one needed early replacement due to loss of telemetry and one patient died of noncardiac cause.

CONCLUSIONS

S-ICD implantation can be performed by cardiologists with a high success rate. Initial experience appears favorable, but further studies are needed with longer follow-up times to assess the safety and efficacy of this strategy compared to conventional devices.

Generator and lead-related complications of implantable cardioverter defibrillators

BACKGROUND

Increase in the number of patients treated with Implantable Cardioverter Defibrillator (ICD) requests more attention regarding its complications.

OBJECTIVES

This study aimed to assess the generator- and lead-related complications at implantation and during follow-up in the patients who were treated with ICD for primary and secondary prevention reasons.

METHODS

We retrospectively reviewed 255 consecutive patients who underwent transvenous ICD implantation for the first time in a 7-year period and were followed-up for 3 years at Tehran Heart Center. The personal and clinical data of the patients as well as specific data on the ICD implantation were retrieved. The frequency of each of the complications was reported and the study variables were compared between the patients with and without complications using Student's t-test and chi-square test where appropriate. P values less than 0.05 were considered as statistically significant.

RESULTS

Out of a total of 525 implanted leads and 255 implanted devices in 255 patients (mean age = 62.57 ± 13.50 years; male = 196 [76.9%]), complications leading to generator or lead replacement occurred in 32 patients (12.5%). The results revealed no significant difference between the patients with and without complications regarding gender and age (P = 0.206 and P = 0.824, respectively). Also, no significant difference was found between the two groups concerning the ejection fraction (P = 0.271). Lead fracture was the most frequent lead-related complication and was observed in 17 patients (6.6%). Besides, it was mainly observed in the RV leads. Generator-related complications leading to generator replacement were observed in 2 patients (0.7%).

CONCLUSIONS

Despite considerable improvements in the ICD technology, the rate of the ICD complications leading to device replacement and surgical revision, especially those related to the leads, is still clinically important.

First experience with the wearable cardioverter defibrillator in the Netherlands

The implantable cardioverter defibrillator (ICD) has significantly improved survival in patients with an increased risk of sudden cardiac death (SCD). The wearable cardioverter defibrillator (WCD) is an alternative to the ICD in patients with a transient ICD indication or those in whom an ICD temporarily cannot be implanted. We describe here the technical details of the WCD and report three patients who were treated with a WCD in an outpatient setting. The WCD allowed the cardiac condition of two patients to improve to such an extent that permanent ICD implantation was deemed unnecessary. This new form of therapy may result in significant cost reduction, avoidance of unnecessary ICD implantation, and increased patient satisfaction.

Managing anticoagulation in patients receiving implantable cardiac devices

A substantial proportion of patients who undergo cardiac rhythm device implantation receive anticoagulation to prevent thromboembolism. Many patients have coexisting cardiovascular diseases treated with antiplatelet therapy. Anticoagulation may increase the risk of hemorrhagic complication, while withdrawal of anticoagulation may increase thromboembolic risk. In this article, we review and describe the available evidence, in order to inform best practice .

An entirely subcutaneous implantable cardioverter-defibrillator

BACKGROUND

Implantable cardioverter-defibrillators (ICDs) prevent sudden death from cardiac causes in selected patients but require the use of transvenous lead systems. To eliminate the need for venous access, we designed and tested an entirely subcutaneous ICD system.

METHODS

First, we conducted two short-term clinical trials to identify a suitable device configuration and assess energy requirements. We evaluated four subcutaneous ICD configurations in 78 patients who were candidates for ICD implantation and subsequently tested the best configuration in 49 additional patients to determine the subcutaneous defibrillation threshold in comparison with that of the standard transvenous ICD. Then we evaluated the long-term use of subcutaneous ICDs in a pilot study, involving 6 patients, which was followed by a trial involving 55 patients.

RESULTS

The best device configuration consisted of a parasternal electrode and a left lateral thoracic pulse generator. This configuration was as effective as a transvenous ICD for terminating induced ventricular fibrillation, albeit with a significantly higher mean (+/-SD) energy requirement (36.6+/-19.8 J vs. 11.1+/-8.5 J). Among patients who received a permanent subcutaneous ICD, ventricular fibrillation was successfully detected in 100% of 137 induced episodes. Induced ventricular fibrillation was converted twice in 58 of 59 patients (98%) with the delivery of 65-J shocks in two consecutive tests. Clinically significant adverse events included two pocket infections and four lead revisions. After a mean of 10+/-1 months, the device had successfully detected and treated all 12 episodes of spontaneous, sustained ventricular tachyarrhythmia.

CONCLUSIONS

In small, nonrandomized studies, an entirely subcutaneous ICD consistently detected and converted ventricular fibrillation induced during electrophysiological testing. The device also successfully detected and treated all 12 episodes of spontaneous, sustained ventricular tachyarrhythmia. (ClinicalTrials.gov numbers, NCT00399217 and NCT00853645.)

Inappropriate Implantable Cardioverter-Defibrillator Therapy

Although improvements in implantable cardioverter-defibrillator (ICD) therapy have taken place, many challenges do remain. Inappropriate delivery of therapy is a big problem that impacts the quality of life of ICD recipients. Although there is now a clear understanding that atrial arrhythmias are the main cause of inappropriate ICD therapies, physicians have not been very successful in preventing them. Additionally, although many tachycardia detection discriminators have been shown to be helpful, it is not clear that there is a particular combination that is ideal for all patients. Until such an algorithm is developed (which may not be possible), a detailed knowledge and use of all available programming options, guided by special characteristics of each unique patient, are the only foreseeable solutions. Finally, one must face the prospect that this problem cannot be vanquished, but only ameliorated.

Ventricular oversensing in 518 patients with implanted cardiac defibrillators: incidence, complications, and solutions

The present study evaluates the incidence of various complications in implanted cardiac defibrillators (ICD) therapy due to ventricular oversensing (VO) and its complications. From June 1998 to May 2005, we retrospectively screened 518 patients (1085.6 patient years) for the occurrence of VO episodes (441 male, 77 female). The overall incidence was 7.3% (n = 38) with inappropriate shock deliveries accounting for 2.3% (n = 12). All VO episodes were caused by either T-wave oversensing (n = 10), myopotentials (n = 8), electrode failure (n = 5), interference with electromagnetic fields (n = 3), double-counting (n = 4), pacemaker interactions (n = 2), or others (n = 2). There were five life-threatening events due to inappropriate ICD reaction. In eight (22%) cases, ICD reprogramming was able to avoid further oversensing episodes (e.g. adaptation of sensitivity, T-wave suppression feature), 13 (35%) patients had to undergo invasive procedures (e.g. electrode replacing) to suppress VO, 16 (43%) were told to avoid the trigger situation, and one demanded to deactivate all ICD therapies because of inappropriate shock delivery. Our data demonstrate that VO is a rare complication, but might lead to life-threatening events. In most cases, VO episodes could be prevented by appropriate ICD reprogramming or avoidance of the initiating trigger.

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.

Fungal infection of implantable cardioverter-defibrillators: Case series of five patients managed over 22 years

BACKGROUND

With the increasing use of implantable cardioverter-defibrillators (ICDs), device complications are becoming more common. Fungal-related ICD infections have rarely been reported, and little is known about the presentation, prevalence, and treatment options for these morbid infections.

OBJECTIVES

The purpose of this study was to characterize the clinical features, treatment, and outcomes of patients with fungal ICD infections.

METHODS

We performed a retrospective review of ICD procedures performed at a single academic center and identified all ICD-related infections managed between 1983 and 2005.

RESULTS

Among a total of 3,648 ICD-related procedures performed between 1983 and 2005, we identified 47 (1.3%) cases of ICD infections, of which 5 (0.1%) were due to a fungal pathogen. Fungal infections were more likely to be associated with abdominal devices, to have a local rather than systemic infection, and to have a longer duration from the original implant to presentation. All patients were treated with ICD system explantation and antifungal therapy.

CONCLUSION

Fungal infection of ICDs is a rare but serious complication of device implantation that must be treated aggressively with complete hardware explantation and prolonged antifungal therapy. Because most infections are late complications and have indolent onsets, a high level of clinical suspicion is required for early diagnosis.

The Rhythm ID Going Head to Head Trial (RIGHT): Design of a Randomized Trial Comparing Competitive Rhythm Discrimination Algorithms in Implantable Cardioverter Defibrillators

BACKGROUND

The implantable cardioverter defibrillator (ICD) has become primary therapy for the prevention of sudden death. One of the major morbidities of ICD use remains inappropriate therapy for supraventricular arrhythmias (SVA). Detection enhancements have increased therapy specificity, but their impact on inappropriate therapy is not well studied. Moreover, ICD manufacturers have developed unique algorithms to meet this goal, with no previous clinical direct comparisons. RIGHT is a randomized, prospective study that will assess the differential efficacy of ICDs from two different manufacturers. It is the first trial to compare directly competitive ICD rhythm discrimination algorithms on a large scale.

OBJECTIVE

The primary objective of this study is to assess arrhythmia discrimination in Guidant versus Medtronic ICDs by comparing the time to first inappropriate therapy after the predischarge visit.

METHODS

The study will enroll approximately 2,000 patients in 100 centers. Patients will be randomized to Guidant or Medtronic using a permuted block design, stratified by center and by single/dual chamber device types. Patients will receive a commercially available Guidant VITALITY 2 family ICD with Rhythm ID or a Medtronic ICD using the Enhanced PR Logic or Wavelet discrimination algorithms, and will be followed according to the schedule shown until a common closing date with a minimum follow-up of 12 months. All events will be reviewed by an independent committee to determine the appropriateness of rhythm classification and therapy delivery.

CONCLUSION

RIGHT is the first randomized, large scale, head-to-head comparison of ICD discrimination algorithms.

Reconfirmation algorithms should be the standard of care in automated external defibrillators

Non-sustained and self-terminating arrhythmias pose a significant challenge during resuscitation. Delivery of a defibrillation shock to a non-shockable rhythm has a poorly understood effect on the heart. The importance of assessing rhythm right up until the delivery of a shock is of increased importance when "blind" shocks are being delivered by automatic defibrillators or minimally trained rescuers. Reconfirmation algorithms are common in current-generation implantable defibrillators but this investigation of current-generation AEDs shows that only 71% of devices presently available have reconfirmation algorithms. A case of spontaneous reversion of a non-sustained arrhythmia is presented. The implications of delivering a defibrillator shock to a non-shockable rhythm are discussed.

Complications of Implantable Cardioverter Defibrillator Therapy in 440 Consecutive Patients

BACKGROUND

Although more than 150,000 implantable cardioverter defibrillators (ICDs) are implanted yearly worldwide, only few studies systematically examined complications of ICD therapy in large patient cohorts.

METHODS

We prospectively analyzed ICD-related complications in 440 consecutive patients who underwent first implantation of an ICD system for primary or secondary prevention of sudden cardiac death within the last 10 years at our institution. All study patients received pectoral nonthoracotomy ICD lead systems with the exception of one patient who had an artificial tricuspid valve.

RESULTS

During 46 +/- 37 months follow-up, 136 of 440 patients (31%) experienced at least one complication including implant procedure-related complications in 43 patients (10%), ICD generator-related complications in 28 patients (6%), lead-related complications in 52 patients (12%), and inappropriate shocks in 54 patients (12%). The most serious complications included one perioperative death due to heart failure (0.2%), two ICD system infections necessitating device removal (0.5%) and two perioperative cerebrovascular strokes (0.5%).

CONCLUSIONS

We conclude that more than one quarter of ICD patients experience complications during a mean follow-up of almost 4 years, although serious complications such as intraoperative death or ICD system infections are rare in patients with nonthoracotomy ICD systems. Recognition of these complications is the prerequisite for advances in ICD technology and management strategies to avoid their recurrence.

An Unusual Obstacle in Lead Extraction

This case report deals with an unusual complication in the removal of an active fixation implantable cardioverter defibrillator (ICD) lead. We were not able to pass the stylet beyond the point of lead fracture and this was subsequently found to be due to the stylet passing between the electrode and the outer layer of the lead insulation. The lead was removed by rotation extraction of the entire lead.

Patient alert in implantable cardioverter defibrillators: toy or tool?

OBJECTIVES

The purpose of this study was to analyze the utility of patient-alert features in implantable cardioverter defibrillators (ICDs).

BACKGROUND

Various alert features producing acoustic warning signals have been implemented in newer generation ICDs, but their role in early detection of system-related complications has not been systematically evaluated.

METHODS

In 240 patients implanted with Medtronic ICD devices, the following alert features were routinely activated: pacing lead impedance <200 or >2,000 Omega, high-voltage lead impedance <10 or >200 Omega, low battery voltage (elective replacement indicator), long charge time (>18 s), >3 shocks delivered per episode, and all therapies in a zone delivered. Alert events occurring during follow-up were assessed in relation to actual findings (hospital charts, chest X-rays, ICD printouts including sensing/pacing/defibrillation threshold tests, episode data) to determine incidence, sensitivity, and specificity of the alert function.

RESULTS

During 12.2 +/- 8.9 months, 24 alert events occurred in the 240 patients (pacing lead impedance, n = 4; high-voltage lead impedance, n = 7; low battery voltage, n = 1; >3 shocks, n = 6; all therapies, n = 6). A total of 22 serious complications (necessitating reprogramming or device/lead replacement) were observed, 14 of which were primarily identified through a patient alert (lead fracture, n = 11; connector defect, n = 1; T-wave oversensing, n = 1; battery depletion, n = 1). This reflects a sensitivity of 64% and a specificity of 96% of the alert function for serious complications. With 14 of 24 patient alerts being caused by serious complications, the positive predictive value reached 58%.

CONCLUSIONS

Patient-alert features are a useful additional tool facilitating early detection of serious ICD complications, but they do not substitute for regular ICD follow-up, because of their low sensitivity.

Use of a wearable defibrillator in terminating tachyarrhythmias in patients at high risk for sudden death: results of the WEARIT/BIROAD

The automatic ICD improves survival in patients with a history of sudden cardiac arrest. However, some patients do not meet the guidelines for ICD implantation or are unable to receive an implantable device. This study tested the hypothesis that these patients could benefit from a wearable cardioverter defibrillator. Patients with symptomatic heart failure and an ejection fraction of <0.30 (WEARIT Study) or patients having complications associated with high risk for sudden death after a myocardial infarction or bypass surgery not receiving an ICD for up to 4 months (BIROAD Study) were enrolled into two studies. After a total of 289 patients had been enrolled in the trial (177 in WEARIT and 112 in BIROAD), prespecified safety and effectiveness guidelines had been met. Six (75%) of eight defibrillation attempts were successful. Six inappropriate shock episodes occurred during 901 months of patient use (0.67% unnecessary shocks per month of use). Twelve deaths occurred during the study 6 sudden deaths: 5 not wearing and 1 incorrectly wearing the device). Most patients tolerated the device although 68 patients quit due to comfort issues or adverse reactions. The results of the present study suggest that a wearable defibrillator is beneficial in detecting and effectively treating ventricular tachyarrhythmias in patients at high risk for sudden death who are not clear candidates for an ICD and may be useful as a bridge to transplantation or ICD in some patients.

Long-Term Outcome of Patients Who Received Implantable Cardioverter Defibrillators for Stable Ventricular Tachycardia

INTRODUCTION

Evidence is inconclusive concerning the role of implantable cardioverter defibrillators (ICDs) to treat patients with hemodynamically stable ventricular tachycardia (VT). The goal of this study was to estimate future risk of unstable ventricular arrhythmias in patients who received ICDs for stable VT.

METHODS AND RESULTS

We reviewed complete ICD follow-up data from 82 patients (age 66.1 +/- 11.3 years; left ventricular ejection fraction 32.3%+/- 11.2%; mean +/- SD) who received ICDs for stable VT. During the follow-up period of 23.6 +/- 21.5 months (mean +/- SD), 15 patients (18%) died, and 10 (12%) developed unstable ventricular arrhythmia, 8 of whom had the unstable arrhythmia as the first arrhythmia after ICD placement. Estimated 2- and 4-year survival in the whole group was 80% and 74%, respectively. Estimated 2- and 4-year probability of any VT and unstable VT was 67% and 77% and 11% and 25%, respectively. There were no differences in age, ejection fraction, sex, underlying heart disease, cycle length, symptoms, baseline electrophysiologic study results, or QRS characteristics of qualifying VT between patients who developed unstable ventricular arrhythmia and patients who did not. Twenty-nine patients (35%) had at least one inappropriate shock, and 11 (13%) underwent further surgery for ICD-related complications.

CONCLUSION

Patients who present with hemodynamically stable VT are at risk for subsequent unstable VT. ICD treatment offers potential salvage of patients with stable VT who subsequently develop unstable VT/ventricular fibrillation, although complications and inappropriate shocks are considerable. No predictors could be found for high and low risk for unstable arrhythmias. These findings support ICD treatment for stable VT survivors.

Implantable Cardioverter Defibrillator Events in Patients with Asymptomatic Nonsustained Ventricular Tachycardia:

Primary prevention trials have demonstrated that patients with coronary disease, reduced left ventricular function, and nonsustained ventricular tachycardia (NSVT) have improved survival with implantable cardioverter defibrillator (ICD) therapy, presumably secondary to effective termination of life-threatening arrhythmias. However, stored intracardiac electrograms were not always available and specific arrhythmias leading to ICD therapy were not always known. We examined the occurrence of ICD events in 51 consecutive patients who match the described patient profile to determine the frequency of appropriate and inappropriate ICD therapy. ICD detections were noted in 18 (35%) patients during a median follow-up period of 13.1 months. Appropriate therapy for sustained ventricular tachycardia (VT)/ventricular fibrillation (VF) occurred in 11 (22%) patients, with appropriate shocks in 8 (16%) patients and appropriate antitachycardia pacing (ATP) in 4 (8%) patients. The time to first appropriate therapy occurred at a mean of 17 +/- 12 months (median 18 months, range 3-36 months). Inappropriate therapy occurred in 5 (10%) patients with inappropriate shocks in 4 patients and inappropriate ATP in 2 patients. Inappropriate therapy was delivered for supraventricular arrhythmias (SVAs) in 4 patients and for T wave oversensing in 1 patient. The reason for shock therapy was unknown in 1 patient (2%) due to ICD malfunction. The mean arrhythmia rate leading to appropriate therapy for VT/VF was 232 +/- 72 beats/min (range 181-400 beats/min), and the mean rate leading to inappropriate therapy for SVT was 168 +/- 10 beats/min (range 160-180 beats/min). Patients with coronary disease and asymptomatic NSVT commonly receive appropriate defibrillator therapy. These results support the need for ICD implantation for primary prevention, with attention to careful programming of the detection rate to prevent inappropriate therapy.

Analysis of implantable cardioverter defibrillator therapy in the Antiarrhythmics Versus Implantable Defibrillators (AVID) Trial

INTRODUCTION

The implantable cardioverter defibrillator (ICD) is commonly used to treat patients with documented sustained ventricular tachycardia (VT) or ventricular fibrillation (VF). Arrhythmia recurrence rates in these patients are high, but which patients will receive a therapy and the forms of arrhythmia recurrence (VT or VF) are poorly understood.

METHODS AND RESULTS

The therapy delivered by the ICD was examined in 449 patients randomized to ICD therapy in the Antiarrhythmics Versus Implantable Defibrillators (AVID) Trial. Events triggering ICD shocks or antitachycardia pacing (ATP) were reviewed for arrhythmia diagnosis, clinical symptoms, activity at the onset of the arrhythmia, and appropriateness and results of therapy. Both shock and ATP therapies were frequent by 2 years, with 68% of patients receiving some therapy or having an arrhythmic death. An appropriate shock was delivered in 53% of patients, and ATP was delivered in 68% of patients who had ATP activated. The first arrhythmia treated in follow-up was diagnosed as VT (63%), VF (13%), supraventricular tachycardia (18%), unknown arrhythmia (3%), or due to ICD malfunction or inappropriate sensing (3%). Acceleration of an arrhythmia by the ICD occurred in 8% of patients who received any therapy. No physical activity consistently preceded arrhythmias, nor did any single clinical factor predict the symptoms of the arrhythmia.

CONCLUSION

Delivery of ICD therapy in AVID patients was common, primarily due to VT. Inappropriate ICD therapy occurred frequently. Use of ICD therapy as a surrogate endpoint for death in clinical trials should be avoided.

R wave undersensing caused by an algorithm intended to enhance sensing specificity in an implantable cardioverter defibrillator

This article reports on a case of ventricular undersensing despite normal R wave amplitudes during sinus rhythm in an ICD patient. Undersensing of ventricular signals was noted without any evidence of lead dislocation or variation in signal amplitude. Undersensing was due to an exceptionally small R wave signal width and a feature of the Biotronik sensing algorithm designed to avoid oversensing. This algorithm, intended to enhance the sensing specificity of the device, requires registration of two consecutive points above the maximum programmed sensitivity for a ventricular sense event. After modifying the algorithm to a single point registration undersensing disappeared.

ICD leads: design and chronic dysfunctions

The treatment of ventricular tachyarrhythmias has changed over the last 10 years. Implantable cardioverter defibrillators (ICDs), once used only as a last resort therapy, have now become the treatment of choice. This change occurred before the first results of randomized studies on ICD therapy in patients with life-threatening ventricular tachyarrhythmias were published by the end of 1997. Technological advances of ICD therapy, in particular the development of transvenous leads, were to a large extent responsible for this change. Modern leads are characterized by their multilumen design that incorporates straight wires and coiled conductors into a single electrode body. Conductors and insulation are sheathed with additional insulation layers. The most frequently used insulating materials are silicone, polyurethane, and fluoropolymers. Lead failures are an important complication of ICD therapy. Fractured conductors, compression, creeping, or insulation defects from abrasion can cause such lead dysfunctions. Chronically implanted leads will inevitably have an increased risk of failure due to defects despite all technological advances. In the light of improving survival figures in patients with ventricular tachyarrhythmias and increasing numbers of ICD implantations, lead failures are becoming a clinical problem of ever increasing importance. Therefore, the question of which lead types necessitate extraction when a certain failure occurs and which leads can be left in place. Despite continuous improvements in lead extraction systems and growing experience in their use, the extraction of any pacemaker or ICD lead is associated with some risk of complications.

Biventricular implantable cardioverter defibrillator and inappropriate shocks

A 53-year-old man with nonischemic cardiomyopathy underwent implantation of a biventricular implantable cardioverter defibrillator (ICD) for symptomatic ventricular tachycardia. He received five shocks while attempting to exercise, 48 hours after implantation. Interrogation of the device revealed double counting of ventricular sensed events by the left and right ventricular leads. Shortening the AV delay and AV nodal blockade (beta-blocker) to promote ventricular pacing failed to prevent additional inappropriate ICD discharges. After detailed consideration of all options including AV nodal ablation, we chose to disconnect the left ventricular lead pending availability of newer devices with sensing functions limited to the right ventricular lead. Since then, the patient has not experienced any additional inappropriate discharges.

Implantable defibrillator event rates in patients with idiopathic dilated cardiomyopathy, nonsustained ventricular tachycardia on Holter and a left ventricular ejection fraction below 30%

OBJECTIVES

This study investigated the incidence of appropriate implantable cardioverter defibrillator (ICD) interventions for ventricular tachycardia (VT) or ventricular fibrillation (VF) in patients with idiopathic dilated cardiomyopathy (IDC) and nonsustained VT in the presence of a left ventricular ejection fraction below 30%, versus in patients with syncope and patients with a history of VT or VF.

BACKGROUND

To date, only limited information is available about the prophylactic use of ICDs in patients with IDC.

METHODS

From January 1993 to July 2000, 101 patients with IDC underwent implantation of ICDs with electrogram storage capability at our institution. Patients were placed into one of three groups according to their clinical presentation: asymptomatic or mildly symptomatic nonsustained VT in the presence of a left ventricular ejection fraction < or = 30% (49 patients, prophylactic group), unexplained syncope or near syncope (26 patients, syncope group) and a history of sustained VT or VF (26 patients, VT/VF group).

RESULTS

During 36 +/- 22 months follow-up, 18 of 49 patients (37%) in the prophylactic group received appropriate shocks for VT or VF, compared with 8 of 26 patients (31%) in the syncope group and with 9 of 26 patients (35%) of the VT/VF group. Multivariate Cox analysis of baseline clinical variables identified left ventricular ejection fraction, atrial fibrillation and a history of sustained VT or VF as predictors for appropriate ICD interventions during follow-up.

CONCLUSIONS

Patients with IDC and prophylactic ICD implantation for nonsustained VT in the presence of a left ventricular ejection fraction < or = 30% had an incidence of appropriate ICD interventions similar to that of patients with a history of syncope or sustained VT or VF. These findings indicate that ICDs may have a role in not only secondary but also primary prevention of sudden death in IDC.

Long-term infection rates associated with the pectoral versus abdominal approach to cardioverter- defibrillator implants

Infection is an uncommon (0% to 6.7%) but serious complication after implantable cardioverter-defibrillator (ICD) implantation. All ICD primary implants, replacements, or revisions performed at the Massachusetts General Hospital between April 1983 and May 1999 were reviewed. A total of 21 ICD-related infections (1.2%) were identified among 1,700 procedures affecting 1.8% of the 1,170 patients who underwent a primary implant, a generator change, or a revision of their systems. The mean follow-up time was 35 +/- 33 months. Of the 959 patients with long-term follow-up, 19 of the 584 patients (3.2%) with abdominal and 2 of the 375 patients (0.5%) with pectoral systems developed ICD-related infections (p = 0.03). There was no significant difference between the infection rate among the 959 primary ICD implants and the 447 replacements or system revisions. Only 5 of the patients (24%) had systemic signs of infection, including fever (T>100.5) and elevated white blood count >12,000. Cultures from the wound revealed staphylococcal species in 16 patients (76%). Nineteen patients were treated with removal of the entire ICD system in addition to intravenous antibiotics for 2 to 4 weeks. A decrease in the incidence of ICD-related infection has occurred since the advent of transvenous pectoral systems. The main organism responsible for ICD infection is Staphylococcus. The mainstay of ICD infection management consists of complete removal of the entire implanted system.

Clinical performance of a specific algorithm to reconfirm self-terminating ventricular arrhythmias in current implantable cardioverter-defibrillators

Inappropriate shock therapy is a frequent problem in patients with implantable cardioverter-defibrillators (ICDs), caused mostly by supraventricular rhythms. Self-terminating ventricular arrhythmias (STVAs), however, may also lead to inappropriate shock discharges even in ICDs with abortive shock capabilities. The aim of this study was to evaluate the clinical performance of a specific ventricular tachycardia/ventricular fibrillation (VT/VF) reconfirmation algorithm implemented in current ICD devices from Medtronic to prevent inappropriate shock discharges due to STVAs. A total of 161 STVA episodes were documented in 59 of 150 patients (39%) within a mean follow-up of 30 +/- 20 months and resulted in 25 inappropriate shock discharges in 15 of 150 patients (10%) despite activation of the reconfirmation algorithm. The first synchronization interval of the algorithm was met in 92% of STVA episodes with and even 38% of STVA episodes without shock delivery. A reduced incidence of inappropriate shocks due to STVAs was found with tachycardia/fibrillation detection intervals (TDI/FDI) programmed to shorter cycle lengths < or =280 ms or the use of the first 2 cycles after the end of charging to be considered for reconfirmation only. Thus, inappropriate shocks due to STVAs still occur in 10% of patients with ICDs despite activation of a specific VT/VF reconfirmation algorithm, and are mainly caused by meeting the first synchronization interval that therefore should be shortened in cycle length. Moreover, to reduce the likelihood of inappropriate shocks, the VF reconfirmation algorithm should be optimized by basing the synchronization intervals exclusively on the FDI with short cycle lengths or using the first 2 cycles for reconfirmation only.

Lead- and device-related complications in the antiarrhythmics versus implantable defibrillators trial

BACKGROUND

Implantation of transvenous implantable cardioverter defibrillators (ICDs) by use of a nonthoracotomy approach has become routine therapy for survivors of life-threatening tachyarrhythmias. The purpose of this study was to identify and prospectively characterize the frequency of lead- and ICD-related complications from the Antiarrhythmics versus Implantable Defibrillators (AVID) Trial.

METHODS AND RESULTS

Between June 1, 1993, and April 7, 1997, 539 patients received nonthoracotomy ICDs either as initial treatment assignment (477) or as crossover from medical management (62). A total of 62 first complications occurred. The subclavian route of insertion resulted in more complications than the cephalic vein route, 46 of 339 (14%) versus 6 of 135 (4%), P = .005, as did the abdominal versus pectoral generator site, 31 of 238 (13%) versus 17 of 291 (6%), P<.02. Most dislodgements and system infections tended to occur in the 3 months after implantation, whereas lead fractures continued to occur throughout follow-up. Failure to use perioperative antibiotics was a predictor of system infection (P = .001).

CONCLUSIONS

These data suggest that cephalic vein access and pectoral generator site may result in fewer complications. The continued occurrence of lead fractures and the need for premature system revision supports the practice of close routine ICD system surveillance.

Peak endocardial acceleration reflects heart contractility also in atrial fibrillation

Previous studies demonstrated that peak endocardial acceleration (PEA) in sinus rhythm is related to LV dP/dtmax. Until now, PEA was never evaluated during R-R interval variations in AF. The aim of this study was to establish the behavior of PEA in AF and the relationship of PEA versus LV dP/dtmax. Six sheep (65 +/- 6 kg) were instrumented with a LV Millar catheter and with an accelerometer lead. AF was induced and PEA, LV dP/dtmax, and ECG were monitored. AF persisted for 5 +/- 1.3 minutes. From sinus rhythm to AF, the heart rate went from 92 +/- 3 to 130 +/- 35 beats/min (P < 0.05), LV dP/dtmax from 684 +/- 18 to 956 +/- 344 mmHg/s (P = NS) and PEA from 0.82 +/- 0.06 to 0.94 +/- 0.33 g (P = NS). The correlation between PEA and LV dP/dtmax was significative in sinus rhythm (r = 0.7, P < 0.05) and in AF (r = 0.8, P < 0.05). A positive relationship was found between the preceding interval and PEA (r = 0.4 +/- 0.07, P < 0.05) and LV dP/dtmax (r = 0.61 +/- 0.08, P < 0.05), while a negative one was found between the prepreceding interval and both PEA (r = -0.39 +/- 0.11, P < 0.05) and LV dP/dtmax (r = -0.64 +/- 0.05, P < 0.05). At the onset of AF, LV dP/dtmax and PEA showed similar changes: beat-to-beat correlation between PEA and LV dP/dtmax was high. As for LV dP/dtmax, PEA is positively related to the preceding interval and negatively related to the prepreceding interval. These data confirm that PEA reflects heart contractility also during AF and hold promise for the use of this sensor in therapeutic implantable devices.

Methods of minimizing inappropriate implantable cardioverter-defibrillator shocks

As more and more patients receive complex implantable cardioverter-defibrillators (ICDs), profound knowledge about the incidence of inappropriate device therapy, the reasons it happens, and the possibilities for prevention is crucial. In this article, the most important prevention algorithms incorporated in current ICD models and their advantages and handicaps are discussed in detail, which should help to guide the device selection for a particular patient. Also, emphasis is put on adjunctive drug therapy and interventional treatment strategies, which are crucial in managing patients with inappropriate ICD shocks.

[Predictors of sudden death in coronary artery disease]

Although advances in the management of acute myocardial infarction have resulted in a decline in long-term risk of sudden death, it continues to be high in certain subsets of patients. Thus, it is important to identify and treat these patients. Left ventricular ejection fraction less than 0.40, frequent premature ventricular ectopy on Holter monitoring, late potentials on signal-averaged electrocardiogram, impaired heart rate variability, abnormal baroreflex sensitivity and inducible sustained monomorphic ventricular tachycardia during electrophysiological study are predictors of sudden death and arrhythmic events. Although the negative predictive value of each factor is high, the positive predictive accuracy is low. Several tests can be combined to obtain higher positive predictive values. In fact, in some studies combined noninvasive tests have been used to select patients for ventricular stimulation study. Some preventive treatment can be applied in these patients. Available data do not justify prophylactic therapy with amiodarone in high-risk survivors of acute myocardial infarction. Sudden death and total mortality have been significantly reduced in postinfarction patients by long-term beta blockade. Hence, beta blockers should be given to all patients with acute myocardial infarction who do not have contraindications to their use. The MADIT study has shown the beneficial effect of implantable cardioverter defibrillator in reducing mortality in patients with prior myocardial infarction, an ejection fraction less than 0.36, asymptomatic nonsustained ventricular tachycardia, and inducible sustained ventricular tachycardia, unsuppressable by procainamide. Besides, several studies are under way to evaluate the prophylactic use of implantable defibrillator for improving survival in high-risk patients.

Implantable defibrillators and antiarrhythmic drugs in patients at risk for lethal arrhythmias

The high mortality rate and frequency of ventricular arrhythmias in patients with congestive heart failure has prompted numerous clinical trials aimed at reducing mortality by addressing arrhythmic death. Recently completed trials have suggested that for patients who have survived cardiac arrest, the preferred treatment may be an implantable cardioverter defibrillator (ICD). From the standpoint of primary prevention, implantable defibrillators and amiodarone have received the most attention. It remains unclear, however, to which patients these studies apply, and if and how the results might be generalized. No available studies confirm an additional benefit of pharmacologic or device-based antiarrhythmic therapy beyond that offered by optimal treatment with beta blockers, angiotensin-converting enzyme inhibitors, and lipid-lowering drugs in the majority of patients with cardiomyopathy. Clinical trials are ongoing to address these issues.