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Reference Values for Chronotropic Index from 1280 Incremental Cycle Ergometry Tests.

Worawan Sirichana, Eric V Neufeld1, Xiaoyan Wang2

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Medicine and Science in Sports and Exercise
|June 5, 2020
PubMed
Summary
This summary is machine-generated.

This study developed a reference equation for the chronotropic index (CI), a measure of heart rate response during exercise, using data from 1280 healthy individuals. The equation helps identify cardiovascular impairment during cardiopulmonary exercise testing.

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Area of Science:

  • Cardiology
  • Exercise Physiology

Background:

  • Clinical cardiopulmonary exercise testing (CPET) is crucial for diagnosing exercise limitation causes.
  • The chronotropic index (CI), the slope of heart rate versus oxygen uptake, aids in identifying cardiovascular impairment.
  • Establishing a reference equation for CI in normal populations is essential for accurate interpretation.

Purpose of the Study:

  • To develop a reference equation for the chronotropic index (CI).
  • To establish normative CI values based on a large cohort of subjects with normal exercise responses.
  • To improve the interpretation of maximal cardiopulmonary exercise tests.

Main Methods:

  • Analysis of 13,728 incremental cycle ergometry tests to identify 1280 normal responses.
  • Inclusion criteria: absence of clinical diagnosis, normal BMI, normal aerobic performance, and no cardiovascular or ventilatory limitations.
  • A linear mixed-model approach was employed to derive the CI reference equation.

Main Results:

  • The final cohort comprised 1280 subjects (54.1% male), aged 18-84 years.
  • Mean CI differed between sexes: 41.2 ± 9.3 beats/L in men vs. 63.4 ± 15.7 L in women.
  • A predictive equation for CI was established: CI = 106.9 + 0.16 × age + 14.3 × sex - 0.31 × height - 0.24 × weight.

Conclusions:

  • A validated reference equation for CI in healthy adults has been developed.
  • CI, alongside V˙O2max, is a valuable tool for interpreting CPET results.
  • High CI may indicate cardiovascular impairment; low CI with low V˙O2max suggests chronotropic insufficiency.