The Human Coronary Collateral Circulation, Its Extracardiac Anastomoses and Their Therapeutic Promotion

Abstract

Cardiovascular disease remains the leading global cause of death, and the number of patients with coronary artery disease (CAD) and exhausted therapeutic options (i.e., percutaneous coronary intervention (PCI), coronary artery bypass grafting (CABG) and medical treatment) is on the rise. Therefore, the evaluation of new therapeutic approaches to offer an alternative treatment strategy for these patients is necessary. A promising research field is the promotion of the coronary collateral circulation, an arterio-arterial network able to prevent or reduce myocardial ischemia in CAD. This review summarizes the basic principles of the human coronary collateral circulation, its extracardiac anastomoses as well as the different therapeutic approaches, especially that of stimulating the extracardiac collateral circulation via permanent occlusion of the internal mammary arteries.

Keywords: collateral artery growth in man; collateral flow index; extracardiac anastomoses; human coronary collateral circulation; permanent internal mammary artery occlusion.

Figure 1

Angiographic demonstration of extracardiac coronary supply. (A) Posterior-anterior projection of the right internal mammary artery (IMA, marked by *) and its connection to the right coronary artery via the pericardiacophrenic branch (marked by +). (B) Lateral projection using the same markers. Noteworthy, additional branches of the IMA (marked by #) heading towards the heart.

Figure 2

Angiographic demonstration of extracardiac coronary supply after coronary artery bypass surgery. (A) Posterior-anterior projection of the left internal mammary artery bypass (marked by a *) on the left anterior descending coronary artery (LAD, marked by a #). Upstream of the bypass anastomosis, retrograde filling of the LAD is incomplete revealing coronary occlusion, which triggered the arteriogenesis of the pericardiacophrenic branch (marked by a +) (B) Lateral projection using the same markers revealing the connection of the pericardiacophrenic branch with the third diagonal branch (marked by III).

Figure 3

Collateral flow index (CFI) measurement. (A) Simultaneous recordings of mean and phasic aortic (red signals, Pao), coronary occlusive (black signals, Poccl) and central venous pressure (blue signals, CVP) immediately before (left side) and during coronary artery occlusion in a patient with poorly functional collaterals. (B) Detection of myocardial ischemia during the coronary artery occlusion by the intracoronary electrocardiogram (i.c.ECG). Immediately after balloon occlusion, the i.c.ECG shows marked electrical alternations with flipped T-waves and ST-segment elevation (marked by the black square). Generally, a CFI of >0.20–0.25 is related to absent signs of ischemia on i.c.ECG during a 1-min proximal coronary occlusion.

Figure 4

Angiographic presentation of two different pathophysiological etiologies of arteriogenesis. (A) Arteriogenesis in the course of hypertensive heart disease with concentric left ventricular hypertrophy. Enlarged myocardial mass is the driving force behind this arterial growth. (B) Arteriogenesis solely initiated by constant elevation of fluid shear stress. Iatrogenic drainage of the left anterior descending artery (LAD) into the right ventricular cavity after myocardial biopsy significantly increased coronary blood flow and consequently vascular size.

Figure 5

Collateral flow index (CFI) measurements of the right coronary artery (RCA) with corresponding electrocardiograms (ECG) after a one-minute proximal coronary balloon occlusion. (A) CFI measured immediately before permanent right internal mammary artery occlusion showing a collateral blood supply of 0.100 and marked ST-deprivations in the ECG as a sign of ischemia (marked with an arrow). (B) Six weeks after the permanent occlusion, CFI increased to 0.250 (+0.150). This augmented coronary blood supply is reflected by the ECG revealing a decreased ischemia without ST-deprivations (marked with an arrow).