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Risk stratification for arrhythmic events in postinfarction patients based on heart rate variability, ambulatory
T G Farrell1, Y Bashir, T Cripps
1Department of Cardiological Sciences, St. George's Hospital Medical School, London, England.
Insights
Impaired heart rate variability and late potentials effectively predict life-threatening arrhythmias and sudden death in heart attack survivors. This simple assessment identifies high-risk patients post-myocardial infarction.
Area of Science:
- Cardiology
- Electrophysiology
- Preventive Medicine
Background:
- Acute myocardial infarction survivors face risks of sudden cardiac death and life-threatening ventricular arrhythmias.
- Accurate prediction of these arrhythmic events is crucial for effective risk stratification and management.
- Existing prognostic factors require further evaluation for their predictive value in this population.
Purpose of the Study:
- To assess the predictive value of heart rate variability (HRV), ambulatory electrocardiographic (ECG) variables, and signal-averaged ECG for arrhythmic events.
- To identify independent predictors of sudden death or life-threatening ventricular arrhythmias in survivors of acute myocardial infarction.
- To evaluate the combined predictive power of key variables for risk stratification.
Main Methods:
- Prospective study of 416 acute myocardial infarction survivors before hospital discharge.
- Assessment of heart rate variability, signal-averaged ECG, and other prognostic factors.
- Follow-up for arrhythmic events and mortality using Kaplan-Meier estimates and Cox regression analysis.
Main Results:
- Significant univariate predictors included impaired HRV (<20 ms), late potentials, ventricular ectopic beat frequency, repetitive ventricular forms, low left ventricular ejection fraction (<40%), and Killip class.
- Impaired HRV, late potentials, and repetitive ventricular forms were identified as independent predictors in stepwise Cox regression.
- The combination of impaired HRV and late potentials demonstrated superior predictive accuracy (sensitivity 58%, positive predictive accuracy 33%, relative risk 18.5) compared to other combinations.
Conclusions:
- Impaired heart rate variability and late potentials are independent predictors of future life-threatening arrhythmias and sudden death in myocardial infarction survivors.
- A simple assessment combining HRV and signal-averaged ECG can effectively identify a high-risk subgroup.
- This approach aids in selecting patients for closer monitoring and potential intervention after acute myocardial infarction.
Abstract:
The value of heart rate variability, ambulatory electrocardiographic (ECG) variables and the signal-averaged ECG in the prediction of arrhythmic events (sudden death or life-threatening ventricular arrhythmias) was assessed before hospital discharge in 416 consecutive survivors of acute myocardial infarction. During the follow-up period (range 1 to 1,112 days), there were 24 arrhythmic events and 47 deaths. The initial relation between several prognostic factors and arrhythmic events was explored with use of the Kaplan-Meier product limit estimates of survival function. Impaired heart rate variability less than 20 ms (p less than 0.0000), late potentials (p less than 0.0000), ventricular ectopic beat frequency (p less than 0.0000), repetitive ventricular forms (p less than 0.0000), left ventricular ejection fraction less than 40% (p less than 0.02) and Killip class (p less than 0.02) were identified as significant univariate predictors of arrhythmic events. When these variables were analyzed by using a stepwise Cox regression model, only impaired heart rate variability, followed by late potentials and repetitive ventricular forms remained independent predictors of arrhythmic events. The combination of impaired heart rate variability and late potentials had a sensitivity of 58%, a positive predictive accuracy of 33% and a relative risk of 18.5 for arrhythmic events and was superior to other combinations including those incorporating left ventricular function, exercise ECG, ventricular ectopic beat frequency and repetitive ventricular forms. These results suggest that a simple method of assessment based on heart rate variability and the signal-averaged ECG can select a small subgroup of survivors of myocardial infarction at high risk of future life-threatening arrhythmias and sudden death.
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