Recent insights into coronary collateral circulation.

Abstract

T he coronary collateral circulation is an alternative source of blood supply to the myocardium jeopardized by failure of the original vessel to provide adequate flow to the major epicardial branches of the coronary artery. There has been considerable debate, however, concerning the functional role of collaterals in humans.1-9 Extensive studies carried out in the past several years in experimental animals, in autopsy materials, or in intact human hearts have confirmed the substantial potential of collaterals in limiting the extent of myocardial ischemia, preventing cell death, and altering the clinical outcome of ischemic heart disease, although these effects depend largely on the rate at which the collateral circulation develops and the magnitude of flow permitted by the newly recruited vessels.Previously More recently, coronary arteriography has permitted correlation of the anatomic appearance of coronary collateral vessels with the underlying coronary artery disease.29 In particular, coronary thrombolysis performed during the first few hours of acute myocardial infarction provided a unique opportunity to evaluate the role of coronary collaterals in minimizing myocardial infarct size.'0-'9 A number of studies suggest that among patients with acute myocardial infarction and unsuccessful intracoronary thrombolytic therapy early after onset of symptoms, subsequent improvement in global function and wall motion in the infarct zone frequently can be expected where residual flow was maintained by extensive collaterals to the region perfused by the infarct-related vessel. 10,12,13,16 We have previously demonstrated that collaterals are a key determinant of the creatine kinase time-activity curve. In patients in whom thrombolysis was unsuccessful but collateral channels are angiographically demonstrable, peak creatine kinase level was attained earlier than in patients without visible collaterals in the absence of recanalization. Thus, collaterals definitely provide significant blood supply to the myocardium at risk'5 (Figure 1)

Coronary Collaterals

“…1 Collateral circulation potentially offers an important alternative source of blood supply when the original vessel fails to provide sufficient blood. 2 Timely enlargement of collaterals may even avoid transmural myocardial infarction (MI) and death in symptomatic patients. 3 As early as in 1956, Baroldi et al 4 demonstrated the presence at birth of mostly corkscrew-shaped collaterals in normal human hearts, with a lumen diameter of 20 to 350 m and lengths ranging from 1 or 2 cm to 4 or 5 cm.…”

The role of NF-kappaB in the angiogenic response of coronary microvessel endothelial cells.

“…The growth of blood vessels is a well-documented physiological response to myocardial infarction (3)(4)(5). The mechanism(s) that regulates the response of cardiac tissue to ischemia and the role of a chemical mediator in the angiogenic process have not been established, although several investigations demonstrated the presence and release of an endothelial cell growth…”

Regression of Collateral Function After Recanalization of Chronic Total Coronary Occlusions

“…[1][2][3] However, even well-developed collaterals may not fully substitute normal coronary flow, and surgical or percutaneous revascularization is often indicated. The incidence of acute myocardial infarction (MI) after recanalization of a chronic total coronary occlusion (CTO) 4,5 suggests that collaterals that are no longer required to uphold myocardial perfusion may regress after revascularization.…”