Coronary Artery Collaterals in Ischaemic Heart Disease: A Review of Mechanisms, Assessment and Prognostic Value

Coronary artery collaterals are specialised networks of endogenous vascular networks that function as a natural bypass, protecting against ischaemic injury in the context of ischaemic heart disease (IHD). Despite their clinical relevance, significant knowledge gaps persist regarding the anatomy and embryological origin, mechanism of collateral growth in IHD, method of assessment, influencing factors, prognostic value, and overall clinical significance. This literature review synthesises current evidence, method of diagnosis and recommendations on the role and importance of coronary artery collaterals. Emerging embryological and mechanistic studies suggest coronary collateral vessel formation may be stimulated during an ischaemic event through angiogenesis, driven by fluid shear stress, hypoxia, and gene expression. Disruption in physiological homeostasis also appears to modulate these angiogenic responses. Nevertheless, key questions remain unresolved, such as whether IHD directly facilitates the development of collateral vessels and how the presence, extent, and functional efficacy of these arteries affect clinical outcomes and survival. Areas requiring further investigation include whether IHD itself facilitates collateral vessel growth and to what degree the existence and extent of collaterals enhance survival outcomes.