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Depressed myocardial function in the goat at high altitude
Journal of Applied Physiology
|September 1, 1976
Summary
Chronic high altitude exposure depresses heart muscle function (Vmax) in goats. This myocardial depression is reversible with long-term, but not short-term, relief from low oxygen levels.
Area of Science:
- Cardiovascular Physiology
- Altitude Medicine
- High Altitude Physiology
Background:
- Cardiac performance often decreases at high altitude.
- The role of myocardial function in this decline is not fully understood.
Purpose of the Study:
- To investigate if depressed myocardial function contributes to reduced cardiac performance during chronic hypobaric hypoxia.
- To assess the reversibility of myocardial function changes upon return to sea level.
Main Methods:
- Six goats were chronically instrumented and studied before, during, and after a 2-week exposure to hypobaric hypoxia (PaO2 44 mmHg).
- Myocardial function was assessed using Vmax, derived from left ventricular pressure measurements.
- Beta-adrenergic blockade and heart pacing were used to standardize conditions.
Main Results:
- Vmax, an index of myocardial function, was significantly depressed (P < 0.01) during chronic hypoxia.
- Stroke volume also decreased at high altitude.
- Acute oxygen administration did not reverse the depressed Vmax at high altitude.
Conclusions:
- Chronic hypobaric hypoxia causes a reversible depression of myocardial function in goats.
- This depression is reversible with chronic but not acute relief from hypoxia.