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Conducting Maximal and Submaximal Endurance Exercise Testing to Measure Physiological and Biological Responses to Acute Exercise in Humans
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Time-of-day variation in cardiovascular response to maximal exercise testing in coronary heart disease patients

Monique Dufour Doiron1, Denis Prud'homme, Pierre Boulay

  • 1School of Kinesiology and Recreation, Faculty of Health Sciences, Université de Moncton, Moncton, NB, Canada.

Applied Physiology, Nutrition, and Metabolism = Physiologie Appliquee, Nutrition Et Metabolisme
|July 12, 2007
PubMed

Insights

Beta-blockers like atenolol and metoprolol show time-of-day variations in their effects on heart rate and blood pressure during exercise tests in coronary heart disease patients. Afternoon tests may reveal more accurate cardiovascular and ischemic responses.

Area of Science:

  • Cardiology
  • Pharmacology
  • Exercise Physiology

Background:

  • Beta-blockers are commonly prescribed for coronary heart disease (CHD).
  • The timing of medication intake can influence drug efficacy and patient response.
  • Understanding diurnal variations in cardiovascular response is crucial for optimizing exercise testing in CHD patients.

Purpose of the Study:

  • To investigate the impact of beta-blockers (atenolol, metoprolol) on exercise heart rate (HR) and rate pressure product (RPP).
  • To compare morning versus afternoon maximal exercise tests (maxET) in CHD patients on beta-blockers.
  • To identify potential time-of-day effects on cardiovascular and ischemic responses during exercise.

Main Methods:

  • Twenty-one CHD patients on atenolol or metoprolol underwent two symptom-limited maxETs.
  • Tests were conducted in the morning (2-3h post-medication) and afternoon (8-10h post-medication).
  • Exercise capacity, perceived exertion, HR, RPP, and electrocardiogram (ECG) responses were analyzed.

Main Results:

  • No significant differences in exercise capacity or perceived exertion were found between morning and afternoon tests.
  • Atenolol showed better HR and RPP control in the afternoon.
  • Metoprolol group had a significantly higher difference in morning vs. afternoon HRmax, with a trend for RPP.
  • Nearly 25% of patients with normal morning tests showed abnormal ECG/ischemia in the afternoon, more so with metoprolol.

Conclusions:

  • Significant time-of-day variations exist in cardiovascular responses to maxET in CHD patients on beta-blockers.
  • Afternoon exercise testing may provide a more sensitive assessment of cardiovascular and ischemic status.
  • These findings highlight the importance of considering medication timing in exercise stress testing protocols.

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