Prevalence of Extracardiac Coronary Collateral Supply Via the Internal Mammary Arteries

In contrast to the extensively studied coronary collateral circulation within the heart, clinical attention has been paid only anecdotally to extracardiac-to-coronary anastomoses. Usually this has been in the form of case reports giving account of angiographically visible anastomoses between the coronary circulation and the internal mammary artery (IMA), typically in the presence of a chronic occlusion of a coronary artery. In the anatomical literature,the most common types of extracardiac anastomoses include bronchial-to-coronary-artery and IMA-to-coronary-artery connections. Anastomoses between the IMA and the coronary circulation have been documented to occur in 12% of post-mortem patients with CAD.

Importantly, hitherto existing observations typically have relied on visual methods insensitive for the adequate detection especially of structurally present but poorly functional anastomoses. On a diagnostic coronary angiogram, collaterals are visible only if the recipient vessel is subtotally stenotic or fully occluded, or can be rendered visible during coronary spasm or by temporary balloon occlusion of the recipient artery and simultaneous injection of contrast medium into the other arteries, respectively. Similarly, the macroscopic pathologic postmortem examination is likely to underestimate the true number of extracardiac coronary collaterals.

The purpose of this study is to determine the in vivo prevalence and functional distribution of IMA-to-coronary collateral supply via both the right and the left coronary artery.