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Both decreased and increased heart rate variability on the standard 10-second electrocardiogram predict cardiac
M C de Bruyne1, J A Kors, A W Hoes
1Department of Epidemiology and Biostatistics, Erasmus University Medical School, Rotterdam, The Netherlands.
Insights
Heart rate variability (HRV) on a 10-second ECG can predict cardiac mortality risk in older adults. Both very low and very high HRV indicate increased risk, with high HRV being a stronger predictor in the elderly.
Area of Science:
- Cardiology
- Geriatrics
- Epidemiology
Background:
- Decreased heart rate variability (HRV) is linked to poor prognosis post-myocardial infarction.
- Population studies on HRV and mortality show conflicting results.
- The prognostic value of HRV in the general elderly population requires further investigation.
Purpose of the Study:
- To investigate the association between HRV, measured by standard deviation of normal R-R intervals (SDNN) on a 10-second ECG, and cardiac and all-cause mortality.
- To assess the risk of mortality across different quartiles of SDNN in an elderly, population-based cohort.
Main Methods:
- The Rotterdam Study, a population-based cohort of individuals aged 55 years and older, was used.
- Data collected between 1990-1996 included 10-second ECGs to calculate SDNN.
- Cox proportional hazards models analyzed mortality risk (cardiac, noncardiac, total) in relation to SDNN quartiles, adjusting for age and sex.
Main Results:
- Subjects in the lowest SDNN quartile had an 80% increased risk of cardiac mortality compared to the third quartile (HR=1.8).
- Subjects in the highest SDNN quartile exhibited an even greater risk of cardiac mortality (HR=2.3).
- These associations remained significant after adjusting for potential confounders.
Conclusions:
- HRV, assessed via a 10-second ECG, is a valuable tool for identifying older adults at increased risk of cardiac mortality.
- In the elderly, higher HRV appears to be a stronger predictor of cardiac mortality than lower HRV.
- Further research is necessary to validate these findings and understand the underlying physiological mechanisms.
Abstract:
Decreased heart rate variability has been associated with an adverse prognosis in patients after myocardial infarction. Studies carried out in the population at large show contradictory results. The authors examined the association between heart rate variability on a standard 10-second electrocardiogram and cardiac and all-cause mortality in the Rotterdam Study, a population-based cohort study of men and women aged > or =55 years, using data collected between 1990 and 1996 (mean follow-up = 4 years). Heart rate variability, taken as the standard deviation of normal R-R intervals (SDNN), was computed by means of the Modular ECG Analysis System. After exclusion of subjects with arrhythmia and those with fewer than six normal R-R intervals, the study population consisted of 2,088 men and 3,184 women. Cox's proportional hazards model was used to examine the age- and sex-adjusted risk for cardiac, noncardiac, and total mortality in relation to quartiles of SDNN, using the third quartile of SDNN as the reference category. Subjects in the lowest quartile of SDNN relative to those in the third quartile had an 80 percent age- and sex-adjusted increased risk for cardiac mortality (hazard ratio = 1.8; 95% confidence interval: 1.0, 3.2). Interestingly, for subjects in the highest quartile of SDNN, an even more pronounced risk for cardiac mortality was present (hazard ratio = 2.3; 95% confidence interval: 1.3, 4.0). Additional adjustment for possible confounders did not materially change the risk estimates. The authors conclude that heart rate variability measured on the standard 10-second electrocardiogram can be used to identify older men and women with an increased risk for cardiac mortality. In the elderly, increased heart rate variability is an even stronger indicator of cardiac mortality than decreased heart rate variability. Further studies are needed to confirm these findings and to elucidate their physiologic meaning.