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Short- and long-term assessment of heart rate variability for risk stratification after acute myocardial infarction
1Department of Cardiological Sciences, St. George's Hospital Medical School, London, United Kingdom.
Insights
Depressed short-term heart rate variability (HRV) after acute myocardial infarction (AMI) predicts 1-year cardiac mortality. Long-term HRV analysis is most effective when limited to patients with low short-term HRV.
Area of Science:
- Cardiology
- Medical Statistics
Background:
- Depressed heart rate variability (HRV) is a significant risk factor post-acute myocardial infarction (AMI).
- Limited comparative data exists on the predictive value of short-term versus long-term HRV for cardiac mortality.
Purpose of the Study:
- To compare the 1-year predictive accuracy of short-term HRV (SDNN) and long-term HRV (HRV index) for total cardiac mortality in AMI patients.
- To evaluate if risk stratification using long-term HRV can be optimized by preselecting patients with depressed short-term HRV.
Main Methods:
- A cohort of 700 consecutive patients post-AMI underwent 24-hour Holter monitoring before hospital discharge.
- Short-term HRV was calculated as SDNN from a 5-minute stationary period; long-term HRV was the HRV index over 24 hours.
- Patients were followed for 1 year to determine total cardiac mortality.
Main Results:
- A moderate correlation was found between SDNN and HRV index (r = 0.51, p <0.001).
- The HRV index demonstrated higher positive predictive accuracy for 1-year mortality (17%-43%) compared to SDNN (13%-18%) across various sensitivities.
- Assessing HRV index in the 35% of patients with the lowest SDNN achieved predictive power comparable to assessing all patients.
Conclusions:
- Lower predischarge short-term HRV (SDNN) is associated with increased 1-year cardiac mortality in AMI patients.
- Long-term HRV analysis for post-infarction risk stratification can be efficiently focused on patients identified with depressed short-term HRV measures.
Abstract:
Depressed heart rate variability (HRV) has been shown to be a powerful and independent risk factor in patients following acute myocardial infarction (AMI). A detailed comparison of the predictive values between short- and long-term HRV has not been made. The predictive value of short-term HRV for 1-year total cardiac mortality was studied in 700 consecutive patients after AMI. All patients underwent 24-hour Holter monitoring before discharge from the hospital (5 to 8 days after AMI) and were followed up for 1 year. Short-term HRV was computed as the standard deviation of all normal RR intervals (SDNN) from a 5-minute stationary period selected from 24-hour Holter electrocardiographic recordings. Long-term HRV was computed as an HRV index over the entire 24 hours. There was a significant but relatively poor correlation between SDNN and HRV index (r = 0.51, p <0.001). The positive predictive accuracy of SDNN for 1-year mortality (13% to 18%) was lower than the HRV index (17% to 43%) over a range of sensitivity of 25% to 75%. Assessment of HRV index in > or = 35% of the patients preselected by the lowest SDNN was able to achieve predictive power similar to that of HRV index assessed in all the patients. These data suggest that lower predischarge short-term HRV is associated with increased 1-year total cardiac mortality in patients after AMI. Analysis of long-term HRV for postinfarction risk stratification can safely be limited to patients preselected by depressed short-term HRV measures.