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Related Experiment Videos

Cardiopulmonary exercise testing in syndrome X

P Montorsi1, P G Agostoni, L Annoni

  • 1Istituto di Cardiologia, University of Milan, Italy.

American Heart Journal
|March 1, 1993
PubMed
Summary

Patients with Syndrome X experience reduced exercise capacity in the afternoon, indicating potential circadian variations in coronary vascular response and a lower ischemic threshold. This may link to abnormal muscle blood flow.

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Area of Science:

  • Cardiology
  • Exercise Physiology
  • Circadian Rhythms

Background:

  • Syndrome X is associated with abnormal coronary blood flow reserve.
  • Physical performance during exercise in Syndrome X is not well understood.
  • Cardiopulmonary exercise testing (CPX) assesses integrated cardiopulmonary and circulatory function.

Purpose of the Study:

  • To investigate the physical performance and physiological responses during exercise in patients with Syndrome X.
  • To determine if circadian variations influence exercise capacity and ischemic thresholds in Syndrome X.
  • To explore potential links between coronary and peripheral circulation responses.

Main Methods:

  • 15 patients with Syndrome X and 15 healthy controls underwent CPX twice daily (8 AM and 4 PM) on two separate occasions.

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  • Evaluated oxygen consumption, exercise thresholds (ventilatory anaerobic and electrocardiographic), double-product, and ST segment depression.
  • Measured plasma norepinephrine concentrations during exercise.

    • Main Results:

    • Syndrome X patients exhibited earlier onset of exercise thresholds and greater ST segment depression in the afternoon (4 PM) compared to morning (8 AM) tests.
    • These afternoon impairments occurred despite similar peak oxygen consumption and double-product.
    • Normal subjects demonstrated reproducible CPX responses, unlike Syndrome X patients.

    Conclusions:

    • Circadian variation in coronary vascular response to exercise may exist in Syndrome X, lowering the ischemic threshold in the afternoon.
    • An earlier onset of the ventilatory anaerobic threshold suggests a potential concomitant abnormal muscular blood flow response.
    • These findings suggest a possible link between coronary and peripheral circulatory dysfunction in Syndrome X.