Abstract 13787: Increased or Stable Chronotropic Index over 7 years Predict Reduced Risks of All-cause and Cardiovascular Mortality among Healthy Middle-aged Men
Background: The chronotropic index (CI), a measure of the ability to increase heart rate (HR) during exercise, is previously reported to predict morbidity and mortality. CI reflects the combined effects of age, resting HR and physical fitness. The predictive value of changes in CI over time has not been studied before, and we tested if change in CI over seven years influences risks of all-cause and cardiovascular (CV) mortality through 28 years.
Methods: CI was calculated after symptom-limited ECG tests among 1420 healthy men at two separate examinations, in 1972-75 and in 1979-82. All-cause and CV mortality were registered in a nationwide survey of all participants’ hospital charts through 2008. CI was defined as measured heart rate reserve (the difference between maximal and resting HR) divided by age-predicted heart rate reserve. Changes in CI between baseline and follow-up were divided into quartiles. Relative risks of all-cause and CV mortality were calculated by Cox proportional hazard regression adjusting for baseline values of physical fitness, age, systolic blood pressure, smoking status, total serum cholesterol and CI.
Results: A total of 740 events of all-cause mortality and 310 events of CV mortality were registered. Incidence of all-cause mortality was lowest in the quartiles with stable or increased CRI (Q3 and Q4). Q3 had a 34% and 31% reduced risk of all-cause and CV mortality respectively, compared to the group with greatest reduction in CI (Q1). The quartile with the greatest increase in CI (Q4) had a 32% and 36% reduced risk of all-cause and CV mortality respectively, compared with Q1 (See table).
Conclusion: Our results indicate that a stable or increased CI reduces the long-term risks of all-cause and CV death. Given the ease with which the chronotropic index can be assessed during a clinical examination, its high predictive value-and since simple measures like physical training can modify this parameter-it should perhaps be more applied in preventive medicine.
- Risk factors
- Heart rate/Heart rate variability
- Cardiovascular disease prevention
- © 2013 by American Heart Association, Inc.