Historical Aspects and Relevance of the Human Coronary Collateral Circulation

In 1669, anastomoses between the right and left coronary artery were first documented by Richard Lower ofAmsterdam. Using post-mortem imaging, a debate followed on the existence of structural inter-coronary anastomoses,which was not resolved before the first half of the 20ieth century in case of the presence of coronary artery disease(CAD), and not before the early 1960ies in case of the normal human coronary circulation by William Fulton. Functionalcoronary collateral measurements during coronary interventions were first performed only in the 1970ies, respectively inthe early 1980ies. In humans, the existence of functional coronary collaterals in the absence of CAD has not been documentedbefore 2003.Though the coronary collateral circulation has been recognized as an alternative source of blood supply to ischemic myocardium,its prognostic significance for the CAD population as a whole has been controversial until recently. The debatewas due to different populations examined (acute versus chronic CAD, varying severity of CAD), to variable definitionsof the term “prognosis”, to insufficient statistical power of the investigation with rare occurrence of prognostic endpoints,to short duration of follow-up and to blunt instruments employed for collateral assessment. Individually, it has been acknowledgedthat a well functioning collateral supply to a myocardial area at risk for necrosis reduces infarct size, preservesventricular function, prevents ventricular remodelling and aneurysm formation. Collectively, evidence has accumulatedonly recently that an extensive coronary collateral circulation is a beneficial prognosticator quoad vitam. In a recentmeta-analysis on the topic, the risk ratio to die from any cause for high vs low or absent collateralization in patients withsubacute myocardial infarction was 0.53 (95% confidence interval 0.15–1.92; p=0.335), and for patients with acute myocardialinfarction, it was 0.63 (95% confidence interval 0.29–1.39; p=0.257)¸ the relative risk to die from any cause forwell vs poorly developed collaterals in patients with stable CAD was 0.59 (95% confidence interval 0.39–0.89), p=0.012.