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Biomedical subjects

A Hallstrom

Publications and source records attributed to A Hallstrom.

At least 37 records · Page 2Linked to original sources
PubMed1994

Interaction of baseline characteristics with the hazard of encainide, flecainide, and moricizine therapy in patients with myocardial infarction. A possible explanation for increased mortality in the Cardiac Arrhythmia Suppression Trial (CAST).

BACKGROUND: The Cardiac Arrhythmia Suppression Trial (CAST) was designed to test the hypothesis that suppression of ventricular ectopy with antiarrhythmic drugs after a myocardial infarction reduces the incidence of sudden arrhythmic death. Patients in whom ventricular ectopy could be suppressed with encainide, flecainide, or moricizine were randomly assigned to receive either active drug or placebo. The encainide and flecainide arms of the study were discontinued in 1989 (CAST-I) and the moricizine arm in 1991 (CAST-II) because of excess mortality. To explore the mechanisms of these adverse outcomes, we examined the interaction of baseline characteristics with the hazard of therapy with encainide, flecainide, or moricizine compared with their respective placebos. METHODS AND RESULTS: CAST-I comprised 755 patients assigned to flecainide or encainide and 743 patients assigned to placebo, whereas in CAST-II, 502 patients received moricizine and 491 patients received placebo. Clinical and laboratory baseline variables of patients receiving active drug and those receiving placebo were similar. In CAST-I patients, there was a significant interaction of active therapy with both all-cause death/cardiac arrest and arrhythmic death/cardiac arrest for non-Q-wave myocardial infarction (total mortality hazard ratios, 1.8 versus 7.9 for Q-wave versus non-Q-wave infarction, P = .03). Ventricular premature depolarization (VPD) frequency > or = 50/h and heart rate > or = 74 beats per minute each interacted significantly with total mortality/cardiac arrest only. In the sicker CAST-II patients (ejection fraction < or = 40%), only diuretic use at baseline interacted significantly with moricizine use for both all-cause death/cardiac arrest and arrhythmic death/cardiac arrest (total mortality hazard ratios, 1.9 versus 0.7 for diuretic use versus no use, P = .01). CONCLUSIONS: Although active treatment in CAST-I was associated with greater mortality than placebo with respect to almost all baseline variables, the therapeutic hazard was more than expected in patients with non-Q-wave myocardial infarction and (for total mortality) frequent premature VPDs and higher heart rates, suggesting that the adverse effect of encainide or flecainide therapy is greater when ischemic and electrical instability are present. The relative hazard of therapy with moricizine in the sicker CAST-II population was greater in those using diuretics. Thus, although these drugs have the common ability to suppress ventricular ectopy after myocardial infarction, their detrimental effects on survival may be mediated by different mechanisms in different populations, emphasizing the complex, poorly understood hazards associated with antiarrhythmic drug treatment.

Arrhythmias, Cardiac↗
PubMed1993

Data monitoring in the cardiac arrhythmia suppression trial.

OBJECTIVE: This report discusses practical aspects of data monitoring in a clinical trial which stopped ahead of schedule due to adverse findings. DESIGN: A review of the considerations and decisions made by the data-monitoring committee of the Cardiac Arrhythmia Suppression Trial (CAST), a randomized, double-blind clinical trial. PATIENTS: CAST consisted of men and women with a recent myocardial infarction, asymptomatic or minimally symptomatic ventricular arrhythmias, and reduced left ventricular ejection fraction. INTERVENTIONS: In CAST, 3 antiarrhythmic agents, encainide, flecainide, and moricizine, were compared against placebo. MAIN OUTCOME MEASURES: The main outcome measures in CAST were arrhythmic death and total mortality. RESULTS: CAST found the 3 agents to be harmful. Encainide and flecainide were stopped first. Subsequently, moricizine was discontinued ahead of schedule. CONCLUSIONS: The complexity of the study design and a midcourse protocol modification raise several data-monitoring issues not previously discussed. These include how to handle apparently dramatic yet unexpected results, the need for flexibility in modifying study design and goals, and the conflict between existing study data and both conventional wisdom and medical practice.

Anti-Arrhythmia Agents↗
PubMed1993

Socioeconomic status and prediction of ventricular fibrillation survival.

OBJECTIVES: The association between socioeconomic status and cardiac arrest is less well known than some other associations with cardiac arrest. We used property tax assessments as a measure of socioeconomic status in a study of victims of out-of-hospital cardiac arrest found in ventricular fibrillation. METHODS: We studied patients attended by the Seattle Fire Department's emergency medical services system between May 1986 and August 1988. During the period studied, 356 episodes met the study criteria; 114 (32%) of these patients survived without major neurologic deficit. Residential property tax assessments were available for 253 of the patients. RESULTS: After adjustments were made for age, witnessed collapse, bystander-initiated cardiopulmonary resuscitation, time from call to paramedic arrival, activity, location of collapse, and chronic morbidity, an association of survival with greater assessed value per living unit was observed. An increase of $50,000 in value per unit was associated with a 1.6-fold increase in survival rate. CONCLUSIONS: Not only are persons in the lower socioeconomic strata at greater risk for cardiac mortality, but they are also less likely to survive an episode of out-of-hospital cardiac arrest.

Aged↗
PubMed1991

Avoiding interpretive pitfalls when assessing arrhythmia suppression after myocardial infarction: insights from the long-term observations of the placebo-treated patients in the Cardiac Arrhythmia Pilot Study (CAPS)

The Cardiac Arrhythmia Pilot Study (CAPS) was a 1 year trial that analyzed the safety and effectiveness of arrhythmia suppression in 502 patients surviving acute myocardial infarction who had greater than or equal to 10 ventricular premature depolarizations/h or greater than or equal to 5 runs of ventricular tachycardia on a Holter recording obtained 6 to 60 days after the acute infarction. Because 100 of these patients received placebo in a double-blind fashion for 1 year, a comprehensive objective analysis was performed of spontaneous arrhythmia changes based on real data rather than statistical estimates. In the CAPS placebo group, 19% developed some serious clinical event in 1 year (death, heart failure, proarrhythmia) that could likely be attributable to antiarrhythmic drug toxicity. A significant reduction in the frequency of ventricular premature depolarizations (p = 0.004) occurred in the first few weeks of "therapy" with a further significant (p less than 0.04) decrease between 3 to 12 months. After initiation of placebo antiarrhythmic therapy, 27% had "apparent ventricular premature depolarization suppression" (greater than or equal to 70% reduction) after one Holter recording evaluation and nearly half (48%) after six Holter recordings to assess suppression were performed.(ABSTRACT TRUNCATED AT 250 WORDS)

Anti-Arrhythmia Agents↗
PubMed1991

Events in the Cardiac Arrhythmia Suppression Trial (CAST): mortality in patients surviving open label titration but not randomized to double-blind therapy.

The patient characteristics and outcomes were studied in the 318 patients who survived open label drug titration in the Cardiac Arrhythmia Suppression Trial (CAST) and who were not randomized to double-blind therapy and in 942 patients, who were randomized to double-blind placebo therapy. The patients randomized to placebo therapy had a lower total mortality or resuscitated cardiac arrest rate (4% vs. 8.5%). However, at baseline, nonrandomized patients were dissimilar from patients randomized to placebo in the following ways: older; lower left ventricular ejection fraction; greater use of digitalis, diuretic drugs and antihypertensive agents; lesser use of beta-adrenoceptor blocking agents and more frequent prior cardiac problems, including runs of ventricular tachycardia and left bundle branch block. A matched comparison that took these inequities into account showed no significant differences in mortality or rate of resuscitation from cardiac arrest between nonrandomized patients and clinically equivalent patients randomized to placebo. Cox regression analysis indicated that two factors significantly increased the hazard ratio for arrhythmic death or resuscitated cardiac arrest in the nonrandomized patients: female gender (4.7, p less than 0.05) and electrocardiographic events (ventricular tachycardia, proarrhythmia, widened QRS complex, heart block, bradycardia) during open label titration (7.0, p less than 0.005). However, some potentially important differences between men and women were not included in the Cox regression model. Of the nonrandomized patients, approximately 70% were not randomized because of lack of suppression of ventricular premature depolarizations or adverse events, or both, and the remaining 30% because of patient or private physician request with no indication of another reason.(ABSTRACT TRUNCATED AT 250 WORDS)

Anilides↗
PubMed1990

Biobehavioral variables and mortality or cardiac arrest in the Cardiac Arrhythmia Pilot Study (CAPS).

The frequency of ventricular premature complexes and the degree of impairment of left ventricular ejection fraction are major predictors of cardiac mortality and sudden death in the year after acute myocardial infarction. Recent studies have implicated psychosocial factors, including depression, the interaction of social isolation and life stress, and type A-B behavior pattern, as predictors of cardiac events, controlling for known parameters of disease severity. However, results tend not to be consistent and are sometimes contradictory. The present investigation was designed to test the predictive association between biobehavioral factors and clinical cardiac events. This evaluation occurred in the context of a prospective clinical trial, the Cardiac Arrhythmia Pilot Study (CAPS). Five-hundred two patients were recruited with greater than or equal to 10 ventricular premature complexes/hour or greater than or equal to 5 episodes of nonsustained ventricular tachycardia, recorded 6 to 60 days after a myocardial infarction. Baseline behavioral studies, conducted in approximately 66% of patients, included psychosocial questionnaires of anxiety, depression, social desirability and support, and type A-B behavior pattern. In addition, blood pressure and pulse rate reactivity to a portable videogame was assessed. The primary outcome was scored on the basis of mortality or cardiac arrest. Results indicated that the type B behavior pattern, higher levels of depression and lower pulse rate reactivity to challenge were significant risk factors for death or cardiac arrest, after adjusting statistically for a set of known clinical predictors of disease severity. The implication of these results for future research relating behavioral factors to cardiac endpoints is discussed.

Affect↗
PubMed1990

Statistical interim monitoring of the Cardiac Arrhythmia Suppression Trial.

The Cardiac Arrythmia Suppression Trial was stopped much earlier than planned. Statistical considerations played a very important role in the decision. Flexible group sequential testing was developed for the trial by implementing a Lan and DeMets procedure with use of the permutation test. We compute P-values from the joint permutation distribution of the test statistics, so we do not need to estimate the sampling distribution which in general is rather difficult to do without strict assumptions. The method also gives an exact test for small samples and allows us to use more complicated or non-Gaussian statistics. We also utilized stochastic curtailment ideas to evaluate various scenarios that might occur during the course of the trial, which assisted the Data and Safety Monitoring Board in making appropriate decisions.

Anti-Arrhythmia Agents↗
PubMed1988

Imbalance in treatment assignments in stratified blocked randomization.

Blocking and stratification are used in preparing randomization assignments to ensure that there will be nearly equal numbers of patients in each treatment group and that the groups will be similar with respect to important covariates. Stratified blocked randomization will create near balance within strata, but imbalance for the total trial may still occur. The variance for the total trial imbalance D is derived and examples from clinical trials are given. Under reasonable assumptions, if the blocking factor is size B in each of K strata, then max D = KB/2 and var D = K(B + 1)/6. These results may be used in planning a trial to estimate the overall imbalance expected for various choices of B and K. A conditional variance is given that allows the probability of an observed imbalance at the completion of a trial to be evaluated. Overall imbalance is about as likely with stratified blocked randomization as with simple randomization unless the total sample size N is appreciably larger than K X B. So long as the blinding is maintained, the block sizes should be chosen to be as small as possible.

Analysis of Variance↗
PubMed1988

Sudden cardiac arrest in Israel: factors associated with successful resuscitation.

Out-of-hospital cardiac arrests were studied in Israel from 1984 to 1985. More than 3,500 patients in cardiac arrest received paramedic care. Eighty-three percent of cases were caused by underlying heart disease. Overall, 17% of patients with arrest caused by heart disease were admitted and 7% were discharged from the hospital. There was a wide variation in the percent discharged among the 15 paramedic service areas, ranging from 0% to 13%. Factors associated with successful resuscitation included witnessed collapse, rhythm of ventricular fibrillation, short interval from collapse to cardiopulmonary resuscitation (CPR) and delivery of advanced cardiac life support, collapse at public location, and bystander initiation of CPR. Improvements in survival are likely to result if CPR is more frequently and promptly initiated and the time to arrival of definitive paramedic care can be improved.

Aged↗
PubMed1987

Spontaneous variability of ventricular arrhythmias in patients at increased risk for sudden death after acute myocardial infarction: consecutive ambulatory electrocardiographic recordings of 88 patients.

The Cardiac Arrhythmia Pilot Study, sponsored by the National Heart, Lung, and Blood Institute, is a multicenter, prospective, randomized, double-blind trial designed to identify patients having 10 or more ventricular premature complexes (VPCs) per hour within 6 to 60 days of acute myocardial infarction. The present investigation selected patients after acute myocardial infarction who had ambulatory electrocardiographic qualifying arrhythmia for CAPS. An additional baseline electrocardiogram was recorded before enrollment in the study to assess baseline spontaneous variability of VPCs. A total of 88 patients (15 women, 73 men, aged 57 +/- 10 years) were studied. The 43 patients (49%) receiving beta-blocking drugs were included because the dose was not altered between the 2 consecutive electrocardiographic recordings. This investigation shows that a 95% reduction in VPCs is required to document a significant drug effect rather than variability alone if 1 day of control and 1 day of treatment electrocardiographic recording are compared. Similarly, based on 1 day of electrocardiographic recording before and after antiarrhythmic therapy, 1,780% increase in VPC frequency is required to establish "arrhythmia aggravation" from an antiarrhythmic drug rather than from variability alone based on a 95% confidence interval. Variability of ventricular arrhythmias is independent of left ventricular function, whereas patients taking beta-blocking therapy tend to have greater VPC variability (p = 0.052), even though VPC frequencies were lower (59 +/- 19 vs 138 +/- 31 VPCs/hour, p less than 0.006) than those not taking beta-blocking drugs.

Adrenergic beta-Antagonists↗
PubMed1987

Lay person use of automatic external defibrillation.

The ability of lay persons to learn and retain defibrillation skills using an automatic external defibrillator (AED) was assessed. Thirty-four family members of cardiac arrest survivors were trained in CPR techniques and defibrillation, and evaluated for performance of skills immediately following training and at six-week and three-month follow-ups. All but two were successfully trained to complete three cycles of CPR interspersed with three defibrillatory shocks in an average of four minutes with the first shock delivered in an average of two minutes. Although there were decrements in the speed and quality of performance at each follow-up period (P less than .01), we conclude that most lay persons can learn to operate an AED safely and under simulated conditions provide defibrillatory shocks an average of eight minutes faster than typical response times of emergency medical technicians. These results suggest that AEDs can be placed in many homes of patients at high risk for cardiac arrest.

Adult↗
PubMed1986

Identification of cardiac arrest by emergency dispatchers.

Prompt identification of cardiac arrest by emergency dispatchers can save valuable time and increase the likelihood of successful resuscitation. The authors reviewed 516 cardiac and 146 non-cardiac calls to identify features of a probable cardiac arrest call. The results indicate that information about sex, location, and activity is of little use in the identification of cardiac arrest. When the patient is over 50 years old and the caller is emotional, the possibility of cardiac arrest is high, suggesting that questions about consciousness and breathing should be asked immediately. Additional information can be obtained or telephone cardiopulmonary resuscitation (CPR) instructions can be given after dispatch of an emergency vehicle.

Age Factors↗
PubMed1986

Home placement of automatic external defibrillators among survivors of ventricular fibrillation.

We performed a study to determine how many patients at highest risk for an episode of ventricular fibrillation (those who have already survived such an event) are potential candidates for automatic external defibrillator placement and accepting of such a device in their homes. All VF survivors in King County, Washington, during 1984 were screened for possible enrollment in the study. Of 95 survivors of out-of-hospital VF, 63 (66%) were eligible and of 47 patients approached, 38 (81%) agreed to participate in the study. These findings suggest that approximately half (product of 66% and 81% acceptance rate equals 53%) of VF survivors potentially could use automatic external defibrillators.

Electric Countershock↗
PubMed1984

Survivors of out-of-hospital cardiac arrest: morbidity and long-term survival.

Sudden cardiac death accounts for two thirds of death due to coronary artery disease. Advanced cardiac life support can now be brought directly to patients with out-of-hospital cardiac arrest, and in this country, as many as 30% of such patients can be discharged from the hospital annually. Certain clinical and resuscitation-related factors are predictive of mortality and morbidity. The best clinical predictors of long-term survival are absence of previous history of myocardial infarction, lack of congestive heart failure during hospitalization, and age less than 60 years. Resuscitation-related predictors of long-term survival are a short time collapse to cardiopulmonary resuscitation (CPR), and a short time from collapse to CPR combined with a short time to provision of definitive care. The majority of cardiac arrest survivors are able to resume previous levels of function.

Emergencies↗
PubMed1984

Automatic external defibrillation: evaluations of its role in the home and in emergency medical services.

Many recent efforts to improve emergency medical services (EMS) and increase survival rates are simply efforts to get defibrillation to patients as rapidly as possible. In the 1960s physicians traveled in mobile coronary care units to bring the defibrillator to cardiac arrest patients. Later, paramedics, rather than physicians, were used. During the late 1970s the concept of early out-of-hospital defibrillation expanded as emergency medical technicians (EMTs) learned to defibrillate. Researchers in several settings confirmed the effectiveness of early defibrillation by EMTs. The automatic detection of ventricular fibrillation (VF) creates new opportunities for the early defibrillation concept. This includes both automatic implantable defibrillators and automatic external defibrillators (AED). The King County, Washington, EMS is conducting two projects to evaluate AEDs. One is a randomized, controlled crossover study in which EMTs use either an AED or a standard manual defibrillator. Outcome measurements include time to countershock, conversion rates, and survival rates. In the second project family members of patients who have survived out-of-hospital VF randomly receive an AED and cardiopulmonary resuscitation (CPR) instruction, or CPR instruction alone. This study was designed to determine whether family members can be trained adequately to use the device effectively. Psychological tests measure the effect of learning about, living with, and using such technology. These studies may help define the role of AEDs in the future management of out-of-hospital VF.

Electric Countershock↗
PubMed1984

The potential use of automatic defibrillators in the home for management of cardiac arrest.

Ventricular fibrillation, an abnormal cardiac rhythm, occurs in at least two-thirds of the 400,000 people who die out of the hospital from sudden cardiac arrest. This rhythm can be treated successfully by electric countershock, a procedure known as defibrillation. The survival rate following such cardiac arrest is directly related to the rapidity of response; the shorter the time from collapse to defibrillation, the more patients will survive. There are two basic options to shorten the time from collapse to defibrillatory shock. The first is to upgrade the emergency medical system. The second is to provide spouses and family members of potential cardiac arrest patients with automatic home defibrillators. This article considers the effectiveness of the second option, home defibrillation, compared with that of an equally costly upgrade in existing emergency medical service systems. The comparisons depend on the existing level of emergency medical service system, the cost of the home defibrillator, and the rate at which a home defibrillator would be used appropriately. The comparisons suggest that in many circumstances home defibrillation is an appropriate option to be considered.

Costs and Cost Analysis↗