Coronary Collateral Growth: Clinical Perspectives and Recent Insights

Abstract

This chapter summarizes recent research on the coronary collateral circulation. The chapter is focused on clinical perspectives and importance of a well-developed coronary collateral circulation, the mechanisms of growth induced by chemical factors and a role for stem cells in the process. Some discussion is devoted to the role of shear stress and mechanical signaling, but because this topic has been reviewed so extensively in the recent past, there is only small mention of its role in the growth of the coronary collateral circulation.Keywords: arteriogenesis, coronary collateral, ischemic heart disease IntroductionAlthough arteriogenesis has been studied for approximately a hundred years, there are still fundamental unanswered questions about the causes of collateral vessel growth, and whether diferent factors control growth at varying points in the maturation process. One line of investigation, spurred by the myriad contributions of Schaper and his colleagues have focused on mechanical shear stress being the main factor that stimulates collateral growth [1][2][3][4]. Although this hypothesis is well-founded on a large body of experimental data, it does not explain other observations that show collateral growth in the absence of altered shear stress [5,6]. Accordingly investigators have proposed that ischemia (via cytokine, chemokine, and growth factor expression), and the consequential inlammation, is the cause of collateral growth, but © 2017 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.assessing it has proven to be diicult due to the unclear lines between ischemic regions, normal circulation, and collateral growth. The hypotheses regarding the causative factor(s) for collateral growth are not mutually exclusive as there are likely many mechanisms that are the principal driver, which vary at various points of the process. For example, even if one maintains that ischemia is the initiating mechanism for collateral growth, it is likely that other stimuli continue the growth of the vessel after the ischemic stimulus has waned. To provide perspective for this chapter, we refer to Figure 1, which summarizes four factors that exert important efects in this adaptive process. The bulk of this chapter will focus on the collateral growth from a clinical perspective, the role of stem cells, and chemical factors involved in this process. We will not extensively review the role that shear stress in coronary collateral growth as this has been reviewed ample times in the past. We also will not review the genetic aspects because the bulk of this information has been derived from studies of collateral growth in vascular beds other than the heart, e.g., skeletal muscle and brain [7,8], although there is some preliminary information about genetic links to collateral growth in patie...

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