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Decreased heart rate variability and its association with increased mortality after acute myocardial infarction
Insights
Reduced heart rate (HR) variability after acute myocardial infarction (AMI) predicts long-term mortality. Lower HR variability indicates a higher risk of death, underscoring its importance in post-MI survival prediction.
Area of Science:
- Cardiology
- Clinical Electrophysiology
- Outcomes Research
Background:
- Heart rate (HR) variability reflects autonomic nervous system balance.
- Decreased HR variability is associated with various cardiovascular conditions, including severe coronary artery disease and congestive heart failure.
- The prognostic value of HR variability following acute myocardial infarction (AMI) requires further elucidation.
Purpose of the Study:
- To investigate whether HR variability predicts long-term survival in patients who have survived AMI.
- To determine the strength of association between pre-discharge HR variability and subsequent mortality.
Main Methods:
- Analysis of 24-hour Holter electrocardiogram recordings from 808 patients 11 ± 3 days post-AMI.
- HR variability quantified as the standard deviation of normal RR intervals (SDNN).
- Longitudinal follow-up for a mean of 31 months, correlating HR variability with mortality, adjusting for clinical and demographic factors.
Main Results:
- HR variability demonstrated the strongest univariate correlation with mortality among all Holter-derived variables.
- Patients with HR variability < 50 ms had a 5.3-fold higher relative risk of mortality compared to those with HR variability > 100 ms.
- HR variability remained a significant independent predictor of mortality after adjustment for ejection fraction and other clinical variables.
Conclusions:
- Reduced HR variability is a potent independent predictor of long-term mortality after AMI.
- This finding suggests a link between diminished autonomic function (increased sympathetic or decreased vagal tone) and adverse outcomes.
- HR variability measurement offers valuable prognostic information for risk stratification in post-myocardial infarction patients.
Abstract:
A high degree of heart rate (HR) variability is found in compensated hearts with good function, whereas HR variability can be decreased with severe coronary artery disease, congestive heart failure, aging and diabetic neuropathy. To test the hypothesis that HR variability is a predictor of long-term survival after acute myocardial infarction (AMI), the Holter tapes of 808 patients who survived AMI were analyzed. Heart rate variability was defined as the standard deviation of all normal RR intervals in a 24-hour continuous electrocardiogram recording made 11 +/- 3 days after AMI. In all patients demographic, clinical and laboratory variables were measured at baseline. Mean follow-up time was 31 months. Of all Holter variables measured, HR variability had the strongest univariate correlation with mortality. The relative risk of mortality was 5.3 times higher in the group with HR variability of less than 50 ms than the group with HR variability of more than 100 ms. HR variability remained a significant predictor of mortality after adjusting for clinical, demographic, other Holter features and ejection fraction. A hypothesis to explain this finding is that decreased HR variability correlates with increased sympathetic or decreased vagal tone, which may predispose to ventricular fibrillation.