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

### **Bigler Marius Reto and Christian Seiler \***

Department of Cardiology, Inselspital, Bern University Hospital, University of Bern, 3010 Bern, Switzerland **\*** Correspondence: christian.seiler@insel.ch; Tel.: +41-31-632-36-93

Received: 30 May 2019; Accepted: 12 July 2019; Published: 30 July 2019

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