Myocardial ischemia and coronary microvascular vasomotion: the impact of hypercholesterolemia.
Coronary microvascular dilation in response to myocardial ischemia is an important defense mechanism for minimizing heart injury. Since myocardial ischemia is an intense stimulus for a living body, many biologic signals that affect the vascular tone are activated. Recent evidence demonstrated that among them, ischemic myocardium-derived factors play dominant roles as mediators of ischemic vasodilation, and that ischemic myocardium releases vasoconstrictor signals simultaneously. Hypercholesterolemia, a major risk factor for coronary atherosclerosis, is known to produce microvascular dysfunction, although it does not produce atherosclerotic lesions at the microvascular level. A recent bioassay study demonstrated that the vasodilator signal transduction from the myocardium to coronary microvessels is severely impaired in hypercholesterolemia. It is likely that redox-sensitive mechanisms play a major role in the impairment of the defensive responses. The present understanding of the mechanism of ischemic vasodilation and the impact of hypercholesterolemia on coronary microvascular regulation shall be discussed in this review.
Komaru
Tatsuya
T
Tohoku University Graduate School of Medicine, Department of Cardiovascular Medicine, 1-1 Seiryo-machi, Aoba-ku, Sendai 980-8574, Japan. komaru@cardio.med.tohoku.ac.jp
Shirato
Kunio
K