Keeping pace with implanted defibrillators.
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Arrhythmias, Cardiac↗
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[Recommendations on the practice of intracavitary diagnostic methods and treatment of cardiac arrhythmias. Diagnostic electrophysiology; interventional electrophysiology; permanent cardiac stimulation; automatic implantable defibrillators].
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Arrhythmias, Cardiac↗
A new evidence base for implantable defibrillator therapy.
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Data Collection↗
[Optimizing 2-electrode arrays of implantable defibrillators].
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Computer Simulation↗
Temporal aspects of improved survival with the implanted defibrillator (MADIT-II).
The present study retrospectively explored the reasons for delay in the onset of survival benefit from the implanted cardioverter defibrillator (ICD) in the Second Multicenter Automatic Defibrillator Implantation Trial. The cumulative probability of cause-specific death over time was estimated by the Kaplan-Meier method and by proportional hazards regression analysis. Early cardiac death survival curves were similar by treatment assignment in the 0- to 12-month period (p = 0.76). Late cardiac death survival curves by treatment assignment in the >12- to 52-month follow-up period were divergent with a lower probability of late cardiac death in the ICD arm compared with conventional therapy group (p <0.001). The time-specific hazard ratios of ICD to conventional therapy for cardiac death in the early and late periods were significantly different from each other (nominal p = 0.004). There was a significant decrease in sudden cardiac death with ICD therapy in the early (p = 0.012) and late (p <0.001) groups. In the early period, the rate of nonsudden cardiac death was significantly higher in the ICD group than in the conventional therapy group (p = 0.003). Rates of late nonsudden cardiac death were similar in the 2 treatment arms (p = 0.11).
Aged↗
Surgical experience with defibrillator implantation using nonthoracotomy leads.
Between October 10, 1989, and June 17, 1991, 109 patients with life-threatening ventricular arrhythmias received an implantable cardioverter-defibrillator at our institution. In 50 patients, nonthoracotomy lead systems consisting of a subcutaneous chest wall patch electrode near the cardiac apex and one (Cardiac Pacemakers, Inc: Endotak C) or two (Medtronic: Transvene) transvenous electrodes were tested. The mean ejection fraction was 0.44 +/- 0.15 with a range from 0.19 to 0.81. Twenty-four patients had a history of open heart operation. In 43 patients the nonthoracotomy lead system was implanted, whereas in 7 patients epicardial patch lead systems were required due to elevated defibrillation thresholds during nonthoracotomy lead testing. There was one perioperative death unrelated to the operative procedure (hydrocephalus internus). Hemorrhage from the subcutaneous patch pocket or the device pocket that required reintervention occurred in 4 patients. During a mean follow-up of 13 +/- 5 months (range, 4 to 26 months) no dislocation of an endocardial lead, insulation defect, or lead fracture has been observed. In 1 patient, the lead system had to be removed due to infection of the subcutaneous patch pocket. The cardiovascular survival rate was 98% at 12 and 18 months, and freedom from sudden cardiac death was 100% at 6 and 12 months. In conclusion, defibrillator implantation using nonthoracotomy lead systems is feasible with a success rate of 86%, and during short-term follow-up no problems related to the lead system such as dislocation, fracture, or insulation defect have occurred.
Adolescent↗
Performance of implantable defibrillator pacing/sensing lead adapters.
The wide variety of implantable defibrillators (ICDs) available from different manufactures and the lack of universal industry standards has resulted in the frequent need for lead adapters at time of ICD implant or change. We analyzed the performance of 81 consecutive ICD sensing/pacing lead adapters used between 1988 and 1993. A total of 66 adapters was used for new epicardial systems, and 15 adapters served as lead connectors during ICD generator replacement. Pacing/sensing lead adapters used were: model LA-201 (n = 28; 34.5%); model 030-308 (n = 26; 32%); model 5866-24 (n = 15; 18.5%); and miscellaneous (n = 12; 15%). After a mean follow-up of 21 +/- 16 months, nine pacing/sensing lead adapters had documented or strongly suspected failure. Most often pacing/sensing lead adapters presented clinically as frequent aborted shocks. Actuarial probability of freedom from failure for model LA-201 was 83% at 1 year, and 72% at 2 and 3 years; this was poorer than for the other sensing leads combined (P = 0.01; hazard ratio = 4.92; 95% confidence intervals = 1.2-20; log-rank test). In conclusion, pacing/sensing lead adapters are a potential source of ICD system complications. Performance is dissimilar among different models; specifically, model LA-201 may not be safe in the long-term, and patients with this lead adapter need to be closely monitored.
Actuarial Analysis↗
Implanted defibrillators and primary prevention of sudden cardiac death: where are we today?
Implanted defibrillators have become a mainstream therapy for the prevention of sudden cardiac death (SCD) from ventricular tachyarrhythmias in patients with chronic coronary artery disease. A decade of studies has confirmed the superiority of ICDs over antiarrhythmic drug therapy in prolonging the life of patients with a prior history of sustained VT or VF. Furthermore, recent studies have examined the role of ICD therapy in the primary prophylaxis against sudden death in patients considered at high risk for ventricular tachyarrhythmias. These studies have revealed that in selected patients with the substrate of chronic coronary artery disease and a ventricular scar, ICDs lead to important relative and absolute reductions in mortality in such patients without a prior history of VT or VF. Clinicians caring for patients with chronic coronary artery disease (CAD) and severe LV dysfunction, who are at a risk of sudden cardiac death, need to carefully consider this information when managing this patient population.
Clinical Trials as Topic↗
Long-term efficacy of an antitachycardia pacemaker and implantable defibrillator combination.
Antitachycardia pacemakers and implantable cardioverter defibrillators (ICD) were implanted in 14 patients to control recurrent hemodynamically stable ventricular tachycardia (VT). All patients underwent extensive preimplant testing in the electrophysiology laboratory documenting that in each patient at least 50 episodes of VT could be reliably terminated by an external model of the antitachycardia pacemaker. The burst scanning mode of antitachycardia pacing was used in all patients. ICDs were implanted solely as a back up should acceleration of VT occur, and all had high nonprogrammable rate cutoffs (mean 191 +/- 12 beats/min). During a mean follow-up of 25 +/- 6 months, 6,029 episodes of VT were treated in the 14 patients. Only 103 ICD discharges were required (approximately one discharge per 60 episodes of VT). Ten of the 14 patients received discharges from their ICDs. No deaths have occurred. All devices remain active and in the automatic mode. Thus, an antitachycardia pacemaker and ICD combination can safely and effectively terminate VT in highly selected patients who are subjected to extensive preimplant testing. In such patients, the vast majority of episodes of VT can be terminated with antitachycardia pacing, and only rarely is a discharge required from the ICD.
Aged↗
Diagnostic value of single versus dual chamber electrograms recorded from an implantable defibrillator.
INTRODUCTION: The clinical utility of ventricular electrograms in comparison to atrial and ventricular electrograms in diagnosing the type of tachycardias recorded by an implantable defibrillator has not been addressed from the standpoint of a clinician's diagnostic accuracy and confidence in that diagnosis. METHODS: Fifty-two tachycardia episodes recorded from dual chamber defibrillators were divided into two tests. The initial test contained only information from the ventricular electrogram and the second test contained information from both the atrial and ventricular electrograms. For each test, the reviewers were asked to provide the specific diagnosis, the originating chamber of origin of the tachycardia, and the confidence of their responses for each question. McNemar's test for matched pairs was used to determine accuracy and an analysis of variance to determine reviewer confidence. RESULTS: The overall accuracy for both the specific diagnosis (61% vs. 79%; p < 0.001) and the chamber of origin (76% vs. 90%; p < 0.001) improved when both the atrial and ventricular electrograms were available for review. Reviewer confidence appeared to correlate with diagnostic accuracy. CONCLUSIONS: The data clearly show the favorable impact of dual chamber defibrillators on the diagnostic accuracy and confidence of clinicians faced with a clinical tachycardia recorded from an implantable defibrillator. Such improvements may translate into more focused and appropriate therapeutic interventions.
Aged↗
Epicardial implantation of the automatic implantable defibrillator by left subcostal thoracotomy.
The automatic implantable defibrillator is a valuable addition to the management of certain patients with ventricular tachycardia and/or fibrillation. The original technique required placement of two transvenous electrodes and an epicardial electrode via a left thoracotomy. We have successfully developed an all-epicardial approach using a left subcostal thoracotomy. Previous experience with epicardial pacemaker implantation by this approach suggested it would be a good technique for implantation of the automatic defibrillator. Early results with this approach have encouraged its continued use.
Electric Countershock↗
Factors determining ICD implantation in drug therapy patients after termination of antiarrythmics versus implantable defibrillators trial.
Because of a significant survival benefit in the defibrillator arm of the Antiarrhythmics versus Implantable Defibrillator (AVID) Trial, patients in the antiarrhythmic drug (AAD) arm were advised to undergo ICD implantation. Despite this recommendation, ICD implantation in AAD patients was variable, with a large number of patients not undergoing ICD implantation. Patients were grouped by those who had been on AAD < 1 year (n = 111) and those on AAD > 1 year (n = 223). Multiple clinical and socioeconomic factors were evaluated to identify those who might be associated with a decision to implant an ICD. The primary reason for patients not undergoing ICD implantation was collected, as well as reasons for a delayed implantation, occurring later than 3 months from study termination. Of 111 patients on AAD for less than 1 year, 53 received an ICD within 3 months compared to 40/223 patients on AAD for more than 1 year (P < 0.001). Patient refusal was the most common reason to not implant an ICD in patients on drug < 1 year; physician recommendation against implantation was the most common in patients on drug > 1 year. Multivariate analysis showed ICD recipients on AAD < 1 year were more likely to be working and have a history of myocardial infarction (MI), while those on AAD > 1 year were more likely to be working, have a history of MI and ventricular fibrillation, and less likely to have experienced syncope, as compared to those who did not get an ICD. Having private insurance may have played a role in younger patients receiving an ICD.
Aged↗
Time dependence of defibrillator benefit after coronary revascularization in the Multicenter Automatic Defibrillator Implantation Trial (MADIT)-II.
OBJECTIVES: The study was designed to assess the effect of elapsed time from coronary revascularization (CR) on the benefit of the implantable cardioverter-defibrillator (ICD) and the risk of sudden cardiac death (SCD) in patients with ischemic left ventricular dysfunction. BACKGROUND: The ICD improves survival in appropriately selected high-risk cardiac patients by 30% to 54%. However, in the Coronary Artery Bypass Graft (CABG)-Patch trial no evidence of improved survival was shown among a similar population of patients in whom an ICD was implanted prophylactically at the time of elective CABG. METHODS: The outcome by time from CR was analyzed in 951 patients in whom a revascularization procedure was performed before enrollment in the Multicenter Automatic Defibrillator Implantation Trial (MADIT)-II. RESULTS: The adjusted hazard ratio (HR) of ICD versus conventional therapy was 0.64 (p = 0.01) among patients enrolled more than six months after CR, whereas no survival benefit with ICD therapy was shown among patients enrolled six months or earlier after CR (HR = 1.19; p = 0.76). In the conventional therapy group, the risk of cardiac death increased significantly with increasing time from CR (p for trend = 0.009), corresponding mainly to a six-fold increase in the risk of SCD among patients enrolled more than six months after CR. CONCLUSIONS: In patients with ischemic left ventricular dysfunction, the efficacy of ICD therapy after CR is time dependent, with a significant life-saving benefit in patients receiving device implantation more than six months after CR. The lack of ICD benefit when implanted early after CR may be related to a relatively low risk of SCD during this time period.
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The RIONI study rationale and design: validation of the first stored electrograms transmitted via home monitoring in patients with implantable defibrillators.
Appropriate and inappropriate therapies of implantable cardioverter defibrillators (ICDs) have a major impact on morbidity and quality of life in ICD recipients. The recently introduced home monitoring of ICD devices is a promising new technique which remotely offers information about the status of the system. Stored intracardiac electrograms (IEGMs), which are essential for correct classification of appropriate and inappropriate ICD discharges, have until now not been available with ICD home monitoring on a day-by-day basis because of limitations of transferable data. We demonstrate the first compressed IEGMs daily transferable via home monitoring (IEGM-online). Validation of these electrograms will be performed in the Reliability of IEGM-Online Interpretation (RIONI) study. A total of 210 episodes of stored IEGMs will be collected by at least 12 European centres. The primary endpoint of this study is to investigate whether the IEGM-online based evaluation of the appropriateness of the ICDs therapeutic decision following episode detection is equivalent to the evaluation based on the complete ICD episode Holter extracted from the IEGM stored. The evaluation is independently done by an expert board of three experienced ICD investigators. The equivalence of the two methods is accepted if the evaluations yield a different conclusion for <10% of all evaluated IEGMs. The conclusion of the study is expected at the beginning of 2007. If RIONI successfully validates IEGMs transmitted via home monitoring, a strong basis for the use of this promising technique will be established.
Death, Sudden, Cardiac↗
Causes of death in the Antiarrhythmics Versus Implantable Defibrillators (AVID) Trial.
OBJECTIVES: This study analyzed the causes of death in the Antiarrhythmics Versus Implantable Defibrillators (AVID) Trial. BACKGROUND: Both implantable cardioverter-defibrillators (ICDs) and antiarrhythmic drugs (AADs) are used as mainstays of treatment for life-threatening ventricular arrhythmias in patients who have survived either ventricular fibrillation or sustained ventricular tachycardia with hemodynamic compromise and serious symptoms. The AVID Trial compared the effectiveness of these two therapies. Survival was better with the ICD. Assessment of the cause of death should help to determine the mechanism of improvement in survival with the ICD. METHODS: Of 1,016 patients enrolled in the AVID Trial, 202 patients died. The mode of death was determined by the unblinded Principal Investigator and independently by an Events Committee, which reviewed materials meticulously blinded with respect to treatment. Deaths were classified as cardiac or noncardiac. Cardiac deaths were further classified as arrhythmic or nonarrhythmic, and causes of noncardiac death were identified. RESULTS: Deaths were more frequent in patients treated with an AAD (n = 122), compared with patients treated with the ICD (n = 80), unadjusted p < 0.001, p = 0.012 adjusted for sequential monitoring. In AVID, 157 deaths were cardiac, and 79 were arrhythmic. The major effect of the ICD was to prevent arrhythmic death (AAD = 55, ICD = 24, nominal unadjusted p < 0.001). Nonarrhythmic cardiac deaths were equal (AAD = 39, ICD = 39). Patients treated with an AAD had a slightly greater incidence of noncardiac deaths (28 vs. 17, p = 0.053), primarily due to pulmonary and renal causes. CONCLUSIONS: The ICD is more effective than an AAD in reducing arrhythmic cardiac death, while nonarrhythmic cardiac death is unchanged. Of note, apparent arrhythmic death still seems to constitute 38% of all cardiac deaths despite treatment with an ICD. However, the ICD remains superior to an AAD in prolonging survival after life-threatening arrhythmias.
Aged↗
Follow-up of patients with unexplained syncope and inducible ventricular tachyarrhythmias: analysis of the AVID registry and an AVID substudy. Antiarrhythmics Versus Implantable Defibrillators.
INTRODUCTION: A prospective registry and substudy were conducted in the Antiarrhythmics Versus Implantable Defibrillators (AVID) Study to clarify the prognosis and recurrent event rate, risk factors, and impact of implantable cardioverter defibrillator (ICD) therapy in patients with unexplained syncope, structural heart disease, and inducible ventricular tachyarrhythmias. METHODS AND RESULTS: Included in the AVID registry were patients from all participating sites who had "out of hospital syncope with structural heart disease and EP-inducible VT/VF with symptoms." In addition, 13 collaborating sites provided more in-depth clinical and electrophysiologic data as part of a formal prospective substudy. Patients in the substudy were followed by local investigators for recurrent arrhythmic events and mortality. Registry patients were tracked for fatal outcomes by the National Death Index. A total of 429 patients with syncope were entered in the AVID registry, of whom 80 participated in the substudy. Of the substudy patients, 21 patients (26%) had inducible polymorphic ventricular tachycardia/ventricular fibrillation (VT/VF), 11 patients (14%) had sustained monomorphic VT <200 beats/min, and 48 patients (60%) had sustained monomorphic VT > or = 200 beats/min. The ICD was used as sole therapy in 75% of the syncope substudy patients (and with antiarrhythmic drug in an additional 9%) and in 59% of the syncope registry patients. Survival rates at 1 and 3 years were 93% and 74% for the substudy patients and 90% and 74% for the registry patients, respectively. Survival of the syncope substudy patients (predominantly treated by ICD) was similar to the VT patients treated by ICD and superior to the VT patients treated by an antiarrhythmic drug (P = 0.05) in the randomized main trial. Mortality events in the substudy were marginally predicted by ejection fraction (P = 0.06) but not by electrophysiologic study-induced arrhythmia. The significant predictor of increased mortality in the registry was age (P = 0.003) and of reduced mortality was treatment with ICD (P = 0.006). CONCLUSION: The results of these analyses support the role of the ICD as primary antiarrhythmic therapy in patients with unexplained syncope, structural heart disease, and inducible VT/VF at electrophysiologic study.
Anti-Arrhythmia Agents↗
Left atrial function is unchanged by implantable defibrillator shocks on hearts in sinus rhythm.
Sixteen patients in sinus rhythm at baseline undergoing implantable cardioverter-defibrillator implantation were monitored with transesophageal echocardiography both before and after direct current cardioversion with currents of 15 to 20 J, for any direct current induced atrial dysfunction. We found no change in the indexes of atrial function or appearance of spontaneous echo contrast in the immediate postshock period by intraoperative transesophageal echocardiography.
Atrial Function, Left↗
In-hospital versus out-of-hospital presentation of life-threatening ventricular arrhythmias predicts survival: results from the AVID Registry. Antiarrhythmics Versus Implantable Defibrillators.
OBJECTIVES: This study describes the outcomes of patients from the Antiarrhythmics Versus Implantable Defibrillators (AVID) Study Registry to determine how the location of ventricular arrhythmia presentation influences survival. BACKGROUND: Most studies of cardiac arrest report outcome following out-of-hospital resuscitation. In contrast, there are minimal data on long-term outcome following in-hospital cardiac arrest. METHODS: The AVID Study was a multicenter, randomized comparison of drug and defibrillator strategies to treat life-threatening ventricular arrhythmias. A Registry was maintained of all patients with sustained ventricular arrhythmias at each study site. The present study includes patients who had AVID-eligible arrhythmias, both randomized and not randomized. Patients with in-hospital and out-of-hospital presentations are compared. Data on long-term mortality were obtained through the National Death Index. RESULTS: The unadjusted mortality rates at one- and two-year follow-ups were 23% and 31.1% for patients with in-hospital presentations, and 10.5% and 16.8% for those with out-of-hospital presentations (p < 0.001), respectively. The adjusted mortality rates at one- and two-year follow-ups were 14.8% and 20.9% for patients with in-hospital presentations, and 8.4% and 14.1% for those with out-of-hospital presentations (p < 0.001), respectively. The adjusted long-term relative risk for in-hospital versus out-of-hospital presentation was 1.6 (95% confidence interval [CI] 1.3-1.9). CONCLUSIONS: Compared with patients with out-of-hospital presentations of life-threatening ventricular arrhythmias not due to a reversible cause, patients with in-hospital presentations have a worse long-term prognosis. Because location of ventricular arrhythmia presentation is an independent predictor of long-term outcome, it should be considered as an element of risk stratification and when planning clinical trials.
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