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In this study, high-risk patients with hypertrophic cardiomyopathy were treated with an implantable defibrillator. Long-term follow-up analysis showed the efficacy of implantable defibrillator therapy, with patients having an appropriate device intervention at a rate of 11%/year, thereby preventing sudden death in an Australian population.
A method of extrapericardial automatic cardioverter defibrillator implantation using bilateral limited anterior thoracotomy approach is described. The approach was used in six patients who have had previous open heart surgery. The defibrillation threshold was 15 joules in four patients and 20 joules in two. One patient died of pulmonary embolism in the tenth postoperative day. All patients were extubated within 0-18 hours. Drainage of a recurrent pleural effusion was required in one patient. This approach was found to be simple, safe, and effective in patients with previous median sternotomy. It may also be useful in patients in whom a cardiac operation may be indicated later in the course of their disease.
The implantable cardioverter-defibrillator (ICD) increases survival of patients who receive the device. However, candidacy rates have not been calculated for a defined population, and the potential effect of the device on the survival of all patients with heart disease has not been estimated. To make these calculations, medical records were reviewed for 1976 to 1988 in a population demographically similar to the white population of the United States. Definite and possible candidates were identified on the basis of American Heart Association/American College of Cardiology guidelines. Candidacy rates ranged from 3.3/100,000 (counting only definite candidates for the entire period) to 8.7/100,000 (counting definite and possible candidates after 1980). Extrapolated to the 1990 U.S. population, estimates ranged from 8,207 to 21,637 new candidates each year. During an average follow-up of 5 years, half of all deaths among candidates had the potential to be delayed by an ICD. In a similar population that has a death rate from heart disease of approximately 280/100,000, 0.6 to 1.6% of subjects have the potential to have their deaths delayed to some extent by an ICD.
The implantable cardioverter-defibrillator (ICD) has become an important mode of therapy for patients at risk for sustained ventricular arrhythmias. While the survival benefit of these devices is clear, adverse consequences are coming to light. The authors report a case of dramatic intraatrial conduction delay associated with repeated ICD shocks, resulting in pacemaker syndrome in a patient who had received both an ICD and a dual-chamber pacemaker. This and other conduction disturbances may become more common as experience with ICDs grows, and may demand adjunctive or alternative therapies to prevent frequent shocks.
BACKGROUND: Implantable cardioverter-defibrillators (ICDs) are effective for primary and secondary prevention of sudden cardiac death due to ventricular arrhythmias. However, despite wide clinical use, there are no generally accepted standardized protocols to characterize and report the output capabilities of ICDs. OBJECTIVE: The objective of this study was to measure and compare the output characteristics of standard-output and high-output ICDs from several manufacturers under a common set of conditions. METHODS: The output characteristics of ICDs randomly selected from hospital stock were measured. The energy delivered for each shock to a range of fixed loads (25-75 Omega) was computed from the voltage waveform and the corresponding load. RESULTS: Delivered energy varied by approximately 4 J over the range of loads tested and varied between devices (high-output 33.8-35 J; standard-output 26.7-28.6 J, at 50 Omega). Leading-edge voltage varied by approximately 6% over the range of loads tested and varied between devices (high-output 738-792 V; standard-output 593-797 V, at 50 Omega). Pulse width varied by a factor of approximately 3 over the range of loads tested and varied between devices (high-output 10-14.5 ms; standard-output 9-12.2 ms, at 50 Omega). Observed variations between devices and with load were significant (P <.001). CONCLUSIONS: Potentially important differences in output characteristics of different ICD systems exist and merit further clinical investigation. The reporting of ICD output characteristics should be standardized. Additionally, it is recommended that manufacturers report output characteristics as a function of load over the typical range of patient loads clinically encountered.
The implantable cardioverter-defibrillator (ICD) is remarkably effective in preventing sudden cardiac death in high-risk patients, but it also has the capacity to provoke or worsen cardiac arrhythmias. Tachyarrhythmias or bradyarrhythmias may result from the delivery of antitachycardia or antibradycardia therapies by tiered-therapy defibrillators. This proarrhythmia, although rarely fatal, increases the morbidity associated with defibrillator therapy. Proarrhythmia is related as much to suboptimal programming as to technical limitations of the device. The proarrhythmic potential of ICD therapy can be minimized by tailoring the "electrical prescription" according to characteristics of the clinical arrhythmia and individual ICD idiosyncrasies.
BACKGROUND: Implantable cardioverter-defibrillator (ICD) therapy is integral to current therapy for ventricular tachycardia. Patients with an ICD frequently require concomitant antiarrhythmic drug therapy. Despite this, some patients still receive frequent ICD therapies for ventricular tachycardia. Therefore, the purpose of this prospective study was to determine the utility of ablation of ventricular tachycardia in patients with an ICD who experience frequent ICD therapies. METHODS AND RESULTS: Twenty-one consecutive patients with frequent ICD therapies despite antiarrhythmic drug therapy were the subjects of this study. The mean age was 69+/-6 years, and 17 were men. The mean ejection fraction was 0.22+/-0.08, and all patients had coronary artery disease. During the 36+/-51 days (range, 4 days to 7 months) preceding the ablation procedures, the patients received 34+/-55 ICD therapies for the clinical ventricular tachycardia, or a mean of 25+/-88 ICD therapies per month. The patients underwent radiofrequency ablation of the presumed clinical ventricular tachycardia by inducing the tachycardia and mapping according to endocardial activation, continuous electrical activity, pace mapping, concealed entrainment, or mid-diastolic potentials. Ablation of the clinical arrhythmia was successful in 76% of patients during 1.4+/-0.6 (range, 1 to 3) ablation procedures and required 12.5+/-9.2 applications of energy. During 11.8+/-10.0 months of follow-up, the frequency of ICD therapies per month decreased from 60+/-80 before successful ablation to 0.1+/-0.3 ICD therapies per month after ablation (P=.01). A quality-of-life assessment demonstrated a significant improvement after successful (P=.02) but not unsuccessful ablation (P=.9). CONCLUSIONS: Radiofrequency ablation of ventricular tachycardia as adjuvant therapy in patients with coronary artery disease and an ICD has a reasonable success rate, significantly reduces ICD therapies, and appears to be associated with an improved quality of life.
Implantable Cardioverter-defibrillator(ICD) has been accepted as an effective therapy for the patients with life-threatening ventricular tachyarrhythmias in our country. Especially, down sizing and further development(e.g. atrial sensing/pacing) of ICD generator allows us to consider the indication of the device in the majority of VT/VF patients. Furthermore, not only secondary prevention trials but also primary prevention trials, comparing ICD with the antiarrhythmic agents(mainly amiodarone), demonstrate a superior efficacy of ICD to improve the patients mortality. Under these circumstances, we have to recognize the strong current toward the ICD at the present time. However, an essential problem of ICD therapy, not to prevent VT/VF recurrence, remains to be resolved.
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.
BACKGROUND: Five years ago, we described a specific ECG pattern of right bundle-branch block and ST-segment elevation in leads V1 through V3 associated with sudden death in patients without demonstrable structural heart disease. Information on long-term outcome has become available due to pooled data on a large cohort of patients with this syndrome who are followed at 33 centers worldwide. METHODS AND RESULTS: Data on 63 patients (57 men; mean age, 38+/-17 years) with the described ECG pattern were analyzed in terms of arrhythmic events and sudden death. Events were analyzed for patients with at least one episode of aborted sudden death or syncope of unknown origin before recognition of the syndrome (symptomatic patients, n=41) and for patients in whom the ECG pattern was recognized by chance or because of screening related to sudden death of a relative (asymptomatic patients, n=22). During a mean follow-up of 34+/-32 months, an arrhythmic event occurred in 14 symptomatic patients (34%) and 6 asymptomatic patients (27%). An automatic defibrillator was implanted in 35 patients, 15 received pharmacological therapy with beta-blockers and/or amiodarone, and 13 did not receive treatment The incidence of arrhythmic events was similar in all therapy groups (log-rank 0.86); however, total mortality was 0% in the implantable defibrillator group, 26% in the pharmacological group, and 31% in the no therapy group (log-rank 0.0005). All mortality was due to sudden death. CONCLUSIONS: Patients without demonstrable structural heart disease and an ECG pattern of right bundle-branch block and ST-segment elevation in leads V1 through V3 are at risk for sudden death. Amiodarone and/or beta-blockers do not protect them against sudden death, and an implantable defibrillator seems to be the present treatment of choice.
The purpose of this study is to report the results and complications associated with transthoracic placement of an implantable defibrillator and their relationship to amiodarone, and to identify clinical predictors of complications. There were 159 men and 41 women. The mean patients age was 61 +/- 11 years, and the mean ejection fraction was 0.33 +/- 0.14. Fifty one percent of patients developed complications including death in 14 patients (7%). Variables which differed in patients who died and those that did not were age, ejection fraction and New York heart failure classifications. Postoperative mortality was unrelated to amiodarone therapy. Twenty patients (10%) developed pneumonia and 15 patients (7.5%) developed respiratory failure. Clinical variables associated with the development of respiratory failure were age, amiodarone therapy and a prior history of pulmonary disease. Patients receiving amiodarone had a higher incidence of an elevated defibrillation threshold (> or = 25 joules) as compared with those not being treated with amiodarone. Clinical factors associated with an elevated defibrillation threshold were a history of a myocardial infarction, prior bypass surgery, and amiodarone. The results of this study demonstrate that placement of an implantable defibrillator using a transthoracic approach is associated with a high incidence of complications. Amiodarone therapy is associated with an increased incidence of pneumonia, respiratory failure, and elevated defibrillation thresholds.
An initial experience with use of the automatic implantable cardioverter-defibrillator (AICD) is described. Twelve patients received the device. One death has occurred during a mean follow-up of 15 months, and it was due to causes other than arrhythmias. Appropriate device discharge terminating a malignant arrhythmia occurred in 9 patients (75%). The observed survival (92%) far exceeds that to be expected in survivors of sudden death treated by conventional means. There have been no operative deaths. Morbidity has been minimal, although three reoperations were required in 2 patients because of lead dislodgment. The AICD has been demonstrated to be effective in treating patients at risk for sudden arrhythmic death. It can be employed safely with minimum morbidity using a variety of implantation techniques.
Amiodarone is an antiarrhythmic agent commonly used in the treatment of supraventricular and ventricular tachyarrhythmias. This article reviews the results and clinical implications of primary and secondary prevention trials in which amiodarone was used in one of the treatment arms. Key post-myocardial infarction primary prevention trials include the European Myocardial Infarct Amiodarone Trial (EMIAT) and the Canadian Amiodarone Myocardial Infarction Trial (CAMIAT), both of which demonstrated that amiodarone reduced arrhythmic but not overall mortality. In congestive heart failure patients, amiodarone was studied as a primary prevention strategy in two pivotal trials: Grupo de Estudio de la Sobrevida en la Insuficiencia Cardiac en Argentina (GESICA) and Amiodarone in Patients With Congestive Heart Failure and Asymptomatic Ventricular Arrhythmia (CHF-STAT). Amiodarone was associated with a neutral overall survival and a trend toward improved survival in nonischemic cardiomyopathy patients in CHF/STAT and improved survival in GESICA. In post-myocardial infarction patients with nonsustained ventricular tachycardia and a depressed ejection fraction, the Multicenter Automatic Defibrillator Implantation Trial (MADIT) demonstrated that implantable cardioverter-defibrillators (ICD) statistically improved survival compared to the antiarrhythmic drug arm, most of whose patients were taking amiodarone. In patients with histories of sustained ventricular tachycardia or ventricular fibrillation, the Cardiac Arrest Study in Seattle: Conventional Versus Amiodarone Drug Evaluation (CASCADE) trial demonstrated that empiric amiodarone lowered arrhythmic recurrence rates compared to other drugs guided by serial Holter or electrophysiologic studies. However, arrhythmic death rates were high in both treatment arms of the study. Several secondary prevention trials, including the Antiarrhythmics Versus Implantable Defibrillators Study (AVID), the Canadian Implantable Defibrillator Study (CIDS), and the Cardiac Arrest Study Hamburg (CASH), have demonstrated the superiority of ICD therapy compared to empiric amiodarone in improving overall survival. Based on the above findings, amiodarone is safe to use in post-myocardial infarction and congestive heart failure patients that need antiarrhythmic therapy. Although amiodarone is effective in treating malignant arrhythmias, high-risk patients should be considered for an ICD as frontline therapy.
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