Implantable cardioverter defibrillator: a Volkswagon or a Rolls Royce: how much will you pay to save a life?
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Defibrillators, Implantable↗
Biomedical subjects
A Hallstrom
Publications and source records attributed to A Hallstrom.
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↗
Action sequence for layperson cardiopulmonary resuscitation.
Although some minor modifications were forged, the general consensus was to maintain most of the current guidelines for phone first/phone fast, no-assisted-ventilation CPR, the A-B-C (vs C-A-B) sequence of CPR, and the recovery position. The decisions to leave these guidelines as they are were based on a lack of evidence to justify the proposed changes, coupled with a reluctance to make revisions that would require major changes in worldwide educational practices without such evidence.Nonetheless, some major changes were made. The time-honored procedure ol pulse check by lay rescuers was eliminated altogether and replaced with an assessment for other signs of circulation. Likewise, it was recommended that even the professional rescuer now check for these other signs of circulation. Although professional rescuers may simultaneously check for a pulse, they should do so only for a short period of time (within 10 seconds). There was also enthusiasm for deleting the ventilation aspect of EMS dispatcher-assisted CPR instructions that are provided to rescuers at the scene who are inexperienced in CPR. lt was made clear, though, that the data are applicable only to adult patients who are receiving CPR and that the data are appropriate most for EMS systems with rapid response times.
Adult↗
Do baseline characteristics accurately discriminate between patients likely versus unlikely to benefit from implantable defibrillator therapy? Evaluation of the Canadian implantable defibrillator study implantable cardioverter defibrillatory efficacy score in the antiarrhythmics versus implantable defibrillators trial.
OBJECTIVE: Our purpose was to evaluate whether baseline characteristics predictive of implantable cardioverter defibrillator (ICD) efficacy in the Canadian Implantable Defibrillator Study (CIDS) are predictive in the Antiarrhythmics Versus Implantable Defibrillators (AVID) Trial. BACKGROUND: ICD therapy is superior to antiarrhythmic drug use in patients with life-threatening arrhythmias. However, identification of subgroups most likely to benefit from ICD therapy may be useful. Data from CIDS suggest that 3 characteristics (age > or =70 years, ejection fraction [EF] < or =0.35, and New York Heart Association class >II) can be combined to reliably categorize patients as likely (> or =2 characteristics) versus unlikely to benefit (<2 characteristics) from ICD therapy. METHODS: The utility of the CIDS categorization of ICD efficacy was assessed by Kaplan-Meier analysis and Cox hazards modeling. The accuracy of the CIDS score was formally tested by evaluating for interaction between categorization of benefit and treatment in a Cox model. RESULTS: ICD therapy was associated with a significantly lower risk of death in the 320 patients categorized as likely to benefit (relative risk [RR] 0.57, 95% confidence interval [CI] 0.37-0.88, P =.01) and a trend toward a lower risk of death in the 689 patients categorized as unlikely to benefit (RR 0.70, 95% CI 0.48-1.03, P =.07). Categorization of benefit was imperfect, as evidenced by a lack of statistical interaction (P =.5). Although 32 of the 42 deaths prevented by ICD therapy in AVID were in patients categorized as likely to benefit, all 42 of these patients had EF values < or =0.35. Neither advanced age nor poorer functional class predicted ICD efficacy in AVID. CONCLUSION: Of the 3 characteristics identified to predict ICD efficacy in CIDS, only depressed EF predicted ICD efficacy in AVID. Thus physicians faced with limited resources might elect to consider ICD therapy over antiarrhythmic drug use in patients with severely depressed EF values.
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Should all trials have a data safety and monitoring committee?
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Clinical Trials as Topic↗
Antiarrhythmic drug use in the implantable defibrillator arm of the Antiarrhythmics Versus Implantable Defibrillators (AVID) Study.
BACKGROUND: Previous retrospective or observational series suggest that many patients with an implantable cardioverter-defibrillator (ICD) will be treated with antiarrhythmic drugs (AADs) to modify the frequency or manifestation of recurrent ventricular arrhythmias. The relative clinical benefit, however, is uncertain, and deleterious interactions can occur. The objective of this clinical investigation was to study the need for, and effects of, concomitant AAD use with the ICD in a prospectively defined cohort. METHODS: All patients randomly assigned to the ICD arm of the Antiarrhythmics Versus Implantable Defibrillators (AVID) study were followed for the addition of class I or III AADs ("crossover") after hospital discharge. Addition of AADs was strictly regulated by AVID protocol. The timing and reasons for crossover and the effects on ventricular arrhythmia recurrence were analyzed. Patients were excluded if they required AADs before hospital discharge after index arrhythmias or if they had no ventricular arrhythmia before initiation of AADs. RESULTS: After a median follow-up of 135 days, 81 (18%) of the 461 eligible patients required AADs and formed the crossover group. The primary reason for crossover was frequent ICD shocks in 64% of patients. The most common AAD selected was amiodarone (in 42%). Independent predictors of crossover were lower ejection fraction, absence of ventricular fibrillation, or presence of nonsyncopal ventricular tachycardia at presentation, prior unexplained syncope, female sex, and history of cigarette smoking. Before AAD use, the 1-year arrhythmia event rate was 90%; after AAD, the event rate was only 64% (P =.0001). The time to first event was extended from 3.9 +/- 0.7 months to 11.2 +/- 1.8 months. There were 1.4 +/- 3.7 fewer ICD therapy events (P =.005) after crossover, predominantly accounted for by reduction in shocks rather than antitachycardia pacing therapies. CONCLUSIONS: The majority of patients who receive ICDs for sustained ventricular tachycardia or ventricular fibrillation can be treated without AADs. Most commonly, AADs are added to combat frequent ICD shocks, which are successfully reduced by AAD therapy.
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Cardiopulmonary resuscitation by chest compression alone or with mouth-to-mouth ventilation.
BACKGROUND: Despite extensive training of citizens of Seattle in cardiopulmonary resuscitation (CPR), bystanders do not perform CPR in almost half of witnessed cardiac arrests. Instructions in chest compression plus mouth-to-mouth ventilation given by dispatchers over the telephone can require 2.4 minutes. In experimental studies, chest compression alone is associated with survival rates similar to those with chest compression plus mouth-to-mouth ventilation. We conducted a randomized study to compare CPR by chest compression alone with CPR by chest compression plus mouth-to-mouth ventilation. METHODS: The setting of the trial was an urban, fire-department-based, emergency-medical-care system with central dispatching. In a randomized manner, telephone dispatchers gave bystanders at the scene of apparent cardiac arrest instructions in either chest compression alone or chest compression plus mouth-to-mouth ventilation. The primary end point was survival to hospital discharge. RESULTS: Data were analyzed for 241 patients randomly assigned to receive chest compression alone and 279 assigned to chest compression plus mouth-to-mouth ventilation. Complete instructions were delivered in 62 percent of episodes for the group receiving chest compression plus mouth-to-mouth ventilation and 81 percent of episodes for the group receiving chest compression alone (P=0.005). Instructions for compression required 1.4 minutes less to complete than instructions for compression plus mouth-to-mouth ventilation. Survival to hospital discharge was better among patients assigned to chest compression alone than among those assigned to chest compression plus mouth-to-mouth ventilation (14.6 percent vs. 10.4 percent), but the difference was not statistically significant (P=0.18). CONCLUSIONS: The outcome after CPR with chest compression alone is similar to that after chest compression with mouth-to-mouth ventilation, and chest compression alone may be the preferred approach for bystanders inexperienced in CPR.
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Comparison of clinical characteristics and frequency of implantable defibrillator use between randomized patients in the Antiarrhythmics Vs Implantable Defibrillators (AVID) trial and nonrandomized registry patients.
In the Antiarrhythmics Vs Implantable Defibrillators (AVID) trial, all patients who meet the study entry criteria are followed in a registry. During the period between June 1993 and June 1995, of 1,117 patients who were enrolled in the registry and met the study entry criteria, 476 were randomized to receive either implantable cardioverter-defibrillators (ICDs) or drug therapy (amiodarone or sotalol), and 641 patients were not randomized for a variety of reasons including: patient refusal (42%); physician refusal (43%); concerns about ability to maintain follow-up over several years (10%), and others (6%). There were no significant differences between the 476 randomized and 641 nonrandomized patients with regard to clinical characteristics, left ventricular function, history of congestive heart failure, medical history, and previous cardiac procedures performed before the index event, except that randomized patients were slightly older (65 vs 62 years) and had a slightly higher prevalence of coronary artery disease and previous myocardial infarction. The index event and location of the index event were not significantly different between the 2 groups. Although 14% of registry patients received neither ICD nor antiarrhythmic drug therapy, ICDs were no more frequently used in the registry patient than antiarrhythmic drugs (45% for ICD vs 42% for drugs). Thus, randomized AVID patients have very similar clinical characteristics, cardiac history, and presenting arrhythmias as to nonrandomized eligible patients. Therefore, the results of the AVID trial may be generalized for all patients with AVID-eligible arrhythmias.
Adolescent↗
Clinical and socioeconomic profile of patients with malignant ventricular arrhythmias in 1993 to 1995. AVID investigators. Antiarrhythmics Versus Implantable Defibrillator.
This report summarizes the clinical and socioeconomic characteristics of the first 542 patients entered into the Antiarrhythmics Versus Implantable Defibrillator (AVID) trial. AVID is a multicenter trial comparing a strategy of initial implantable cardioverter-defibrillator placement to initial antiarrhythmic drug therapy in preventing death in patients resuscitated from cardiac arrest who were not taking amiodarone and who did not have an implantable cardioverter-defibrillator in place at the time of the index event. These patients were randomly assigned to immediate defibrillator placement or to "best" medical therapy. Clinical and socioeconomic histories were collected by interview using standard terms developed for the study. Patients without (group 1) and with (group 2) a history of prior cardiac arrest were compared. The mean age of the 542 patients was 65 +/- 10 years, most were men, white, had coronary disease, and were highly functional despite the fact that only a minority were employed. Almost all had some form of health insurance. At the time of the index event, few were taking any therapy to prevent cardiac arrest, even in the group of patients with a history of previous cardiac arrest. Thus, the clinical and socioeconomic profile of patients resuscitated from sudden cardiac death entered into the AVID study is generally as expected. There is a striking absence of any attempt at chronic therapy to prevent cardiac arrest in most patients with a prior ventricular tachycardia or ventricular fibrillation.
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Predictive value for future arrhythmic events of fractal dimension, a measure of time clustering of ventricular premature complexes, after myocardial infarction. CAST Investigators. Cardia Arrhythmia Suppression Trial.
OBJECTIVES: Our objective was to test fractal dimension (D), a measure of clustering of ventricular premature complexes (VPCs), on entry Holter recording as a predictor of future arrhythmic death and other-cause mortality in postinfarction patients in the Cardiac Arrhythmic Suppression Trial (CAST). BACKGROUND: Nonlinear dynamic methods of signal processing are being applied in medicine to provide new insights into apparently "chaotic" biologic events, including cardiac arrhythmias. One such application is the derivation of a fractal D to describe the clustering of VPCs in time. METHODS: Baseline Holter recordings were analyzed in blinded manner for 484 patients: 237 died or had a resuscitated cardiac arrest during follow-up, and 247 matched patients had no events. Fractal D, measured in four ways, was assessed as a predictor using Cox regression. RESULTS: One measure of D (high resolution D) was a significant univariate (relative hazard ratio 0.79 per SD change, p = 0.011) and multivariate (hazard ratio 0.75, p = 0.046) predictor of arrhythmic death but not other death (univariate p = 0.95, relative hazard 0.95, p = 0.66). Fractal D was greater (VPCs less clustered) in those patients free of arrhythmic events. On subgroup analysis, the predictive value of D resided in the randomized patient group (i.e., those who showed VPC suppression during initial antiarrhythmic drug titration and were randomized to blinded therapy with active drug or placebo) (multivariate hazard ratio 0.57, p = 0.001). CONCLUSIONS: A high resolution fractal D was predictive of arrhythmic (but not nonarrhythmic) death in a large postinfarction cohort. Further study of this new signal processing approach to ambulatory electrocardiographic recording will be of interest.
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Logrank, play the winner, power and ethics.
We show by simulation and numerical integration techniques that power is largely unaffected by play the winner strategies in a typical chronic disease mortality trial utilizing the logrank test. This raises the issue of the ethics of equal allocation in such a setting.
Anti-Arrhythmia Agents↗
Masking drug treatments in the Cardiac Arrhythmia Pilot Study (CAPS). FASHP for the CAPS Investigators.
The effectiveness of masking in the Cardiac Arrhythmia Suppression Study (CAPS) was assessed by surveying investigators and study coordinators. CAPS patients were assigned one of five treatments: encainide, flecainide, imipramine, moricizine, or placebo. Had all treatments appeared identical and equal numbers of patients been assigned to each, 20% of guesses of treatment assignment would be correct by chance alone. Since neither was possible in CAPS, higher rates of correct guessing were expected. Overall, respondents correctly identified treatment 39% of the time. Investigators identified the drug 30% of the time with rates of 20%, 24%, 37%, 20%, and 55% for the five treatment groups, respectively, whereas coordinators identified the treatments 47% of the time with scores of 42%, 45%, 50%, 40%, and 60%. Side effects and a suboptimal masking design detracted from masking; electrocardiographic changes did not imipramine, which caused characteristic side effects, was the most frequently identified active treatment. Scores were higher for investigators who had prior experience with the drugs, but scores did not improve over the course of the trial. Findings suggest that to improve masking all drugs should have been matched in appearance or persons evaluating treatments should not have been allowed to see the drugs.
Anti-Arrhythmia Agents↗
A simulation study used to design the sequential monitoring plan for a clinical trial.
In designing a sequential monitoring plan for the AVID (Antiarrhythmics Versus Implantable Defibrillators) study, a multi-centred clinical trial, we completed a simulation study to help ourselves and the Data Safety Monitoring Board understand the implications of various monitoring plans. In particular, we compared three test statistics and three use functions. Simulation was based on approximate trial parameters and two plausible but distinct alternative hypotheses. The power to detect a difference between the two treatment arms was computed as a function of time. The simulated results illuminate several of the important statistical and ethical issues involved in selecting a sequential monitoring plan and illustrate how one can use simulations to design a clinical trial.
Amiodarone↗
Toward vital status sweeps: a case history in sequential monitoring.
We use data from the Cardiac Arrhythmia Suppression Trial (CAST) to demonstrate the sensitivity of sequential monitoring to the timeliness of survival data. In CAST vital status sweeps were not routinely performed prior to the times of sequential analysis. Examination of the delay between death and reporting of death shows that the change in the time of sequential analysis by even as few as several months can have dramatic impact on the results of the sequential analysis.
Anti-Arrhythmia Agents↗
Prediction of cardiac death in patients with a very low ejection fraction after myocardial infarction: a Cardiac Arrhythmia Suppression Trial (CAST) study.
The Cardiac Arrhythmia Suppression Trial (CAST) database was analyzed with a Cox proportional hazards regression model to predict the mortality of patients with very poor left ventricular systolic function (ejection fraction < or = .20). Predictors of total death or cardiac arrest were (relative risk), QRS duration (1.10/10 msec increase), coronary artery bypass grafting (0.38), basal heart rate (1.26/10 min-1 increase), diastolic blood pressure (0.79/10 mm Hg increase), diabetes mellitus (1.59), EF (0.94/1 U increase), and ease of suppression (the ability to suppress ambient ventricular ectopy on the lowest dose of the first randomly chosen CAST drug) (0.64). Predictors of arrhythmic death or arrhythmic cardiac arrest included thrombolysis (0.44), coronary artery bypass grafting (0.38), diuretic use (1.71), heart rate (1.21/10 min-1 increase), calcium channel blocker use (1.69), and QRS duration (1.10/10 msec increase). Thus easily measurable clinical and laboratory variables help predict prognosis in this clinically important subgroup. The pathophysiologic basis for and the clinical implications of the ease of ventricular arrhythmia suppression correlating with prognosis requires further study.
Blood Pressure↗
Relations between heart failure, ejection fraction, arrhythmia suppression and mortality: analysis of the Cardiac Arrhythmia Suppression Trial.
OBJECTIVES: We studied the relations between heart failure, ejection fraction, arrhythmia suppression and mortality. BACKGROUND: Both left ventricular ejection fraction and functional class of heart failure are strongly associated with mortality after acute myocardial infarction. Both are also related to the presence of ventricular arrhythmias and have been identified as factors related to the ability to suppress ventricular arrhythmias. Little has been reported about the relations between these two factors and arrhythmia suppression or mortality. METHODS: Baseline data from the Cardiac Arrhythmia Suppression Trial were used to define several categories of heart failure and to relate both the resulting categories and ejection fraction to arrhythmia suppression and mortality using logistic and survival regression analytic methodologies. RESULTS: Regardless of the prospective baseline definition of heart failure used, the data consistently showed that heart failure was a more powerful predictor of subsequent congestive heart failure events and arrhythmia suppression and was equally powerful in predicting death. However, each variable provided incremental information when included in the prediction model. Heart failure and ejection fraction appeared to be independent predictors of death. Interactions were observed: A low ejection fraction was more predictive of failure of arrhythmia suppression in patients with than without evidence of heart failure before or at baseline; a low ejection fraction was more predictive of subsequent congestive heart failure events in patients without than with evidence of heart failure before or at baseline. CONCLUSIONS: Although heart failure as a prognostic feature appears to be somewhat superior to ejection fraction, both are powerful predictors of arrhythmia suppression and cardiac events in patients with ventricular arrhythmia after myocardial infarction. Each provides incremental prediction.
Arrhythmias, Cardiac↗
An AVID dissent.
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Anti-Arrhythmia Agents↗
New insights into the definition and meaning of proarrhythmia during initiation of antiarrhythmic drug therapy from the Cardiac Arrhythmia Suppression Trial and its pilot study. The CAST and CAPS Investigators.
OBJECTIVES: This study was undertaken to determine the characteristics of worsening ventricular arrhythmia during antiarrhythmic drug titration. BACKGROUND: Proarrhythmia is an evolving concept in cardiology. Its definition, incidence and clinical significance in various patient settings require refinement. METHODS: The impact of early proarrhythmia was analyzed in 3,840 patients in the Cardiac Arrhythmia Suppression Trial (CAST). RESULTS: Drug therapy did not affect the incidence of new, sustained but nonfatal ventricular tachycardia (placebo 0.5%, active drug 0.4%). Nevertheless, there was a threefold increase in arrhythmic death (placebo 0.5% vs. active drug 1.6%). The incidence of increased ventricular premature depolarizations was equivalent (3% to 5%) for the three study drugs and indistinguishable from that seen with placebo. Patients with increased ventricular premature depolarizations on the first drug tested had fewer at baseline (65 +/- 94 vs. 137 +/- 260 per hour; mean +/- SD) (p < 0.01). When increased ventricular premature depolarizations occurred with the first drug, they were much more likely also to be present with the second drug (for example, 42% vs. 5%, p < 0.001). Increased ventricular premature depolarizations during initiation of therapy independently predicted increased risk of subsequent arrhythmic death (independent relative risk 2.34, p = 0.0053) in the absence of continued antiarrhythmic drug therapy. CONCLUSIONS: The overall incidence of early worsening of arrhythmia in the present study was low. In the absence of placebo control, the incidence of proarrhythmia will be overestimated. Increased ventricular premature depolarizations had characteristics that suggest they often represent spontaneous variability rather than proarrhythmia. The main finding is that markedly increased ventricular premature depolarizations during drug titration predict long-term increased risk of arrhythmic death in this patient population despite absence of long-term antiarrhythmic drug therapy.
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