Cardiac Adaptation to Chronic Hypoxia

Publisher Summary This chapter discusses cardiac adaptation to chronic hypoxia. The degree of hypoxic injury depends on the intensity and duration of the hypoxic stimulus, and also on the level of cardiac tolerance to oxygen deprivation. Chronic myocardial hypoxia, the result of disproportion between oxygen supply and demand at the tissue level, may be induced by several mechanisms. The most common causes are undoubtedly (1) ischemic hypoxia, induced by the reduction or interruption of the coronary blood flow, and (2) systemic hypoxia, characterized by a drop in PO 2 in the arterial blood. One can also add (3) anemic hypoxia, in which the arterial PO 2 is normal, but the oxygen transport capacity of the blood is decreased. On the other hand, the most frequent causes of raised oxygen consumption are increased physical activity, mental stress, or administration of substances with positive inotropic and chronotropic effects. The most frequently used experimental model in research on chronic hypoxia is that of high altitude, either as seen in the mountain environment or as simulated under laboratory conditions in a normobaric or hypobaric chamber.