Coronary circulation in the failing heart

Abstract

In congestive heart failure, vascular resistance increases because of vasoconstriction caused by activation of the neurohumoral system. On the other hand, vasodilatory responses can partially compensate for vasoconstriction by increasing vasodilatory substances. Although vasoconstrictive forces predominate as a whole, there is heterogeneity in the responses of different vascular beds to vasoactive agents. Especially, as for coronary circulation in the setting of heart failure, many factors may cause disturbances in coronary circulation. Thus, in this review, we discuss from the point of view of neurohumoral modification of coronary flow, coronary flow reserve, endothelial dependent and independent control of vasomotor tone, vascular responses in relation to vessel size or the severity of heart disease, and mechanical factors that determine coronary circulation. Throughout these discussions, the mechanism responsible for the reduction in coronary dilatory capacity is also described. Depressed myocardial blood flow and a blunted flow response to cardiovascular stimulation together may be one important mechanism responsible for the progression of disease in patients with cardiac dysfunction. Accordingly, even though it is not known whether abnormal coronary circulation is a cause or effect of heart failure, the treatment of impaired coronary flow reserve seems to be essential in the care of patients with cardiac dysfunction.