Key result
Experimental coarctation of the aorta in rats reduced papillary muscle tension by 46%, whereas adaptation to high-altitude hypoxia increased tension by 30% compared to controls.
Why the study?
How do experimental coarctation of the aorta and high-altitude hypoxia affect the contractile function of the rat myocardium?
How do experimental coarctation of the aorta and high-altitude hypoxia affect the contractile function of the rat myocardium?
Chronic pressure overload (coarctation) impairs myocardial contractility, whereas chronic hypoxic load (high-altitude hypoxia) enhances it in rat models.
Rat data should not guide patient care; leaves open translation of pressure overload versus hypoxia effects on human contractility.
After 15-18 months of experimental coarctation of the aorta, the weight of the rat left ventricle increased by 94%. Papillary muscle strips developed 46% less tension than strips of the same thickness from control hearts. The average rate of tension development was 53% below controls. Strips from hypertrophied hearts featured three characteristics probably associated with impairment of excitation-contraction coupling, namely a decreasing ability to respond to high-stimulation frequency, a decrease in the degree of potentiation by paired pulse stimulation, and an increase in the extent of incomplete relaxation at high-contraction rate as compared to controls. After 6-7 weeks of adaptation to high-altitude hypoxia, the rat papillary muscle strips taken from non-hypertrophied left ventricle developed 30% more tension than strips of the same thickness from control hearts. These strips showed a higher contraction amplitude at high-stimulation rates, and an increase in the degree of potentiation by paired pulse stimulation.
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Меерсон et al. (2008) studied Cardiac adaptation to chronic load. Experimental coarctation of the aorta and high-altitude hypoxia vs. Control hearts was evaluated on Tension development in papillary muscle strips. Experimental coarctation of the aorta in rats reduced papillary muscle tension by 46%, whereas adaptation to high-altitude hypoxia increased tension by 30% compared to controls.
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