Factors causing variability in formation of coronary collaterals during coronary artery disease

Coronary artery disease (CAD) is one of the major causes of death worldwide. CAD is narrowing of coronary arteries that prevents adequate blood supply to the heart muscle and results in acute coronary syndrome which includes unstable angina and myocardial infarction. The only remedy for it is to restore the perfusion through percutaneous intervention and grafting which may sometime cause reperfusion injury and other complications. Coronary collaterals are small inter-arterial connections that act as natural bypass which provide blood flow to the vascular territory, when the artery supplying to it gets obstructed. Acute collateral recruitment can occurs as a remedy for these adverse cardiac events. Various methods of therapies considered for the promotion and sustenance of functional coronary collaterals. The determinants of human coronary collaterals give clear evidence for prognosis in CAD and a new insight for further therapeutic promotion of coronary collaterals. This review mainly focuses on various studies done on coronary collaterals and the effect of various demographic, morphological and cardiovascular risk factors on the formation of coronary collaterals during obstructive CAD. Many studies have proven that various independent variables such as morphology of coronary artery, location of the lesion, duration of the occlusion, coronary dominance, biochemical factors, and cardiac risk factors, such as diabetes, hypertension, also affect collateral formation. The current update review gives a holistic view on coronary collaterals and findings of various authors on the effect of these independent variables on collateral formation.