The imbalance between oxygen demand and supply as a potential mechanism in the pathophysiology of heart failure: The role of microvascular growth and abnormalities

In heart failure, a deficient oxygen supply often is a primary cause for myocardial dysfunction. The reverse however, may also be true; the changes that occur in the failing heart may predispose for the existence of tissue hypoxia, which further affects the function of the heart. Specifically, myocardial hypertrophy and accelerated heart rhythm enhance oxygen demand, while supply is hampered short by endothelial dysfunction and diffusion barriers (such as fibrosis, arterial hyperplasia, and myocyte hypertrophy). Another contributory factor may be deficient growth of the microvasculature that does not keep pace with the rate of myocardial hypertrophy. Fewer microvessels have been observed in many forms of cardiomyopathies. On the other hand, some distinct forms of cardiomyopathies are characterized by the compensatory growth of microvessels, or even excess angiogenesis. This review summarizes the knowledge that has been gathered on this topic thus far and discusses factors that mediate myocardial microvessel growth. Furthermore, a paradigm is presented in which the rate of microvessel growth predicts, at least in part, the degree of myocardial dysfunction. Therapies aimed at the restoration of the microcirculation are proposed to preserve and improve myocardial function.