Clinical research: acute myocardial infarction
Prediction of sudden cardiac death after myocardial infarction in the beta-blocking era

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Abstract

Objectives

This study assessed the predictive power of arrhythmia risk markers after an acute myocardial infarction (AMI).

Background

Several risk variables have been suggested to predict the occurrence of sudden cardiac death (SCD), but the utility of these variables has not been well established among patients using medical therapy according to contemporary guidelines.

Methods

A consecutive series of 700 patients with AMI was studied. The end points were total mortality, SCD, and nonsudden cardiac death (non-SCD). Nonsustained ventricular tachycardia (nsVT), ejection fraction (EF), heart rate variability, baroreflex sensitivity, signal-averaged electrocardiogram (SAECG), QT dispersion, and QRS duration were analyzed (n = 675). Beta-blocking therapy was used by 97% of the patients at discharge and by 95% at one and two years after AMI.

Results

During a mean (±SD) follow-up of 43 ± 15 months, 37 non-SCDs (5.5%) and 22 SCDs (3.2%) occurred. All arrhythmia risk variables differed between the survivors and those with non-SCD (e.g., the standard deviation of N-N intervals was 98 ± 32 vs. 74 ± 21 ms [p < 0.001] and the QRS duration was 103 ± 22 vs.89 ± 16 ms [p < 0.001]). Sudden cardiac death was weakly predicted only by reduced EF (<0.40; p < 0.05), nsVT (p < 0.05), and abnormal SAECG (p < 0.05), but not by autonomic markers or standard ECG variables. The positive predictive accuracy of EF, nsVT, and abnormal SAECG as predictors of SCD was relatively low (8%, 12%, and 13%, respectively).

Conclusions

The common arrhythmia risk variables, particularly the autonomic and standard ECG markers, have limited predictive power in identifying patients at risk of SCD after AMI in the beta-blocking era.

Abbreviations

AMI
acute myocardial infarction
BRS
baroreflex sensitivity
ECG
electrocardiogram
EF
ejection fraction
HRV
heat rate variability
ICD
implantable cardioverter-defibrillator
nsVT
nonsustained ventricular tachycardia
NYHA
New York Heart Association
SAECG
signal-averaged electrocardiogram
SCD
sudden cardiac death

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This study was supported by the Medical Council of the Academy of Science, Helsinki, Finland, and the Foundation for Cardiovascular Research, Helsinki, Finland. Dr. Myerburg is supported, in part, by the American Heart Association Chair in Cardiovascular Research at the University of Miami and by the Louis Lemberg Chair in Cardiology.