Protective Effects of Chronic Intermittent Hypoxia Against Myocardial Ischemia/Reperfusion Injury

Abstract

Accumulated evidence has shown that adaptation to chronic hypobaric intermittent hypoxia (IH) increases myocardial tolerance to the subsequent severe hypoxia, Ca2+ overload, or ischemia/reperfusion (I/R) injury. Attractively, this form of protection is noninvasive, persists longer than ischemic preconditioning, and has less side effects such as right ventricular hypertrophy compared with the chronic continuous hypoxia. The cardioprotective effects are largely dependent on the degree and duration of IH. Therefore, to identify suitable cycle length, the number of hypoxic episodes per day, degree, and duration of chronic hypobaric IH is important for clinical application. In addition, elucidation of the mechanisms underlying chronic IH-induced cardioprotection is of basic and clinical importance. To address these issues, this chapter focuses primarily on the cardioprotective effects of chronic hypobaric IH in the improvement of myocardial contractile dysfunction and in the reduction of arrhythmias due to Ca2+ overload or I/R injury. The recent progresses in the understanding of the mechanisms, especially related to the cellular adaptation, are discussed. The knowledge we have got from this area should provide new insights into the understanding of the intrinsic defensive mechanism and have impact on the exploring of new therapeutic approaches in the protection of the heart against ischemic heart diseases and other stress.