Definition of the best prediction criteria of the time domain signal-averaged electrocardiogram for serious arrhythmic events in the postinfarction period. The Cardiac Arrhythmia Suppression Trial/Signal-Averaged Electrocardiogram (CAST/SAECG) Substudy Investigators.

OBJECTIVES: The goal of this study was to establish guidelines for the prognostic use of the time domain signal-averaged electrocardiogram (ECG) after myocardial infarction. BACKGROUND: Previous studies of the prognostic use of the signal-averaged ECG in postinfarction patients had one or more of the following limitations: a small study group, empiric definition of an abnormal recording and possible bias in the selection of high risk groups or classification of arrhythmic events, or both. To correct for these limitations, a substudy was conducted in conjunction with the Cardiac Arrhythmia Suppression Trial (CAST). METHODS: Ten centers recruited 1,211 patients with acute myocardial infarction without application of the ejection fraction or Holter criteria restrictions of the main CAST protocol. Several clinical variables, ventricular arrhythmias on the Holter recording, ejection fraction and six signal-averaged ECG variables were analyzed. Patients with bundle branch block were excluded from the analysis, and the remaining 1,158 were followed for up to 1 year after infarction. The classification of arrhythmic events was reviewed independently by the CAST Events Committee. RESULTS: During an average (+/- SD) follow-up of 10.3 +/- 3.2 months, 45 patients had a serious arrhythmic event (nonfatal ventricular tachycardia or sudden cardiac arrhythmic death). A Cox regression analysis with only the six signal-averaged ECG variables indicated that the filtered QRS duration at 40 Hz > or = 120 ms (QRSD-40 Hz) at a cutpoint > or = 120 ms was the most predictive criterion of arrhythmic events. In a regression analysis that included all clinical, Holter and ejection fraction variables, a QRSD-40 Hz > or = 120 ms was the most significant predictor (p < 0.0001). The positive, negative and total predictive accuracy and odds ratio for QRSD-40 Hz > or = 120 ms were 17%, 98%, 88% and 8.4, respectively, and improved to 32%, 97%, 94% and 16.7, respectively, after combination with ejection fraction < or = 40% and complex ventricular arrhythmias on the Holter recording. CONCLUSIONS: The signal-averaged ECG predicts serious arrhythmic events in the first year after infarction better than do clinical, ejection fraction and ventricular arrhythmia variables, and QRSD-40 Hz > or = 120 ms provides the best predictive criterion in this clinical setting.

Single vs. double data entry in CAST.

An experiment was conducted to determine whether, using microcomputer-based data entry, double data entry (DE) significantly lowers data entry keying error rates when compared to single entry (SE). Clinical centers of the Cardiac Arrhythmia Suppression Trial (CAST) participated in a randomized crossover design experiment comparing SE and DE. A total of 42,278 data items (fields) were checked for consistency between the paper data form and the computer database. The overall error rate was 19 per 10,000 fields. Error rates were 22 and 15 per 10,000 fields for SE and DE, respectively; P = .09 by Poisson regression. DE took 37% longer than SE, costing each clinic approximately an extra 90 min per month.

Increased risk of death and cardiac arrest from encainide and flecainide in patients after non-Q-wave acute myocardial infarction in the Cardiac Arrhythmia Suppression Trial. CAST Investigators.

This report examines whether in the Cardiac Arrhythmia Suppression Trial death and cardiac arrest from encainide, flecainide and moricizine during the titration phase and from encainide and flecainide during the follow-up phase were related to presence (Q-wave acute myocardial infarction [Q-AMI]) or absence (non-Q-AMI) of pathologic Q waves. In all, 2,371 patients (70% with Q-AMI, 26% with non-Q-AMI, and 4% unknown) entered the titration phase, starting 117 +/- 163 days after index AMI and lasting for an average of 21 days. For the titration phase, no significant differences existed between Q-AMI and non-Q-AMI patients for death and cardiac arrest rate, ventricular premature complex suppression rate, and nonrandomization rate. A total of 1,498 patients entered the follow-up phase of an average of 10 months (starting 129 +/- 158 days after the index AMI), and were randomized to encainide or flecainide, or their matching placebos. In the placebo group, non-Q-AMI patients had a significantly lower rate of death and cardiac arrest than Q-AMI patients (1.0 and 4.6%, respectively; p = 0.04). Encainide and flecainide significantly elevated death and cardiac arrest rate in both non-Q-AMI patients (8.7%, p less than 0.01) and Q-AMI patients (7.8%, p = 0.04). The relative risk for encainide or flecainide over placebo in the non-Q-AMI patients was 8.7, which was significantly higher than 1.7 observed for the Q-AMI patients (p = 0.03). None of the baseline characteristics had any significant interaction with encainide or flecainide.(ABSTRACT TRUNCATED AT 250 WORDS)

Events in the Cardiac Arrhythmia Suppression Trial (CAST): mortality in the entire population enrolled.

To test the hypothesis that suppression of ventricular arrhythmias by antiarrhythmic drugs after myocardial infarction improves survival, the Cardiac Arrhythmia Suppression Trial (CAST) was initiated. Suppression was evaluated before randomization during an open label titration period. Patients whose arrhythmias were suppressed were randomized in the main study and those whose arrhythmias were partially suppressed were randomized in a substudy. Overall survival and survival free of arrhythmic death or cardiac arrest were lower [corrected] in patients treated with encainide or flecainide than in patients treated with placebo. However, the death rate in patients randomized to placebo therapy was lower than expected. This report describes the survival experience of all patients enrolled in CAST and compares it with mortality in other studies of patients with ventricular arrhythmias after myocardial infarction. As of April 18, 1989, 2,371 patients had enrolled in CAST and entered prerandomization, open label titration: 1,913 (81%) were randomized to double-blind, placebo-controlled therapy (1,775 patients whose arrhythmias were suppressed and 138 patients whose arrhythmias were partially suppressed during open label titration); and 458 patients (19%) were not randomized because they were still in titration, had died during titration or had withdrawn. Including all patients who enrolled in CAST, the actuarial (Kaplan-Meier) estimate of 1-year mortality was 10.3%. To estimate the "natural" mortality rate of patients enrolled in CAST, an analysis was done that adjusted for deaths that might be attributable to encainide or flecainide treatment either during prerandomization, open label drug titration or after randomization. Because the censoring procedure excluded patients treated with encainide or flecainide after randomization, the mortality estimate will be less than the unadjusted mortality estimate of 10.3%.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac arrest and resuscitation: a tale of 29 cities.

Published reports of out-of-hospital cardiac arrest give widely varying results. The variation in survival rates within each type of system is due, in part, to variation in definitions. To determine other reasons for differences in survival rates, we reviewed published studies conducted from 1967 to 1988 on 39 emergency medical services programs from 29 different locations. These programs could be grouped into five types of prehospital systems based on the personnel who deliver CPR, defibrillation, medications, and endotracheal intubation; the five systems were three types of single-response systems (basic emergency medical technician [EMT], EMT-defibrillation [EMT-D], and paramedic) and two double-response systems (EMT/paramedic and EMT-D/paramedic). Reported discharge rates ranged from 2% to 25% for all cardiac rhythms and from 3% to 33% for ventricular fibrillation. The lowest survival rates occurred in single-response systems and the highest rates in double-response systems, although there was considerable variation within each type of system. Hypothetical survival curves suggest that the ability to resuscitate is a function of time, type, and sequence of therapy. Survival appears to be highest in double-response systems because CPR is started early. We speculate that early CPR permits definitive procedures, including defibrillation, medications, and intubation, to be more effective.