REVIEW Extracardiac Coronary Arterial Anastomoses MARIOS LOUKAS, 1 * MICHAEL HANNA, 1 JUSTIN CHEN, 1 R. SHANE TUBBS, 2 AND ROBERT H. ANDERSON 3 1 Department of Anatomical Sciences, School of Medicine, St. George’s University, Grenada, West Indies 2 Children’s Hospital, Division Pediatric Neurosurgery, Birmingham, Alabama 3 Cardiac Unit, Institute of Child Health, University College, London, United Kingdom The collateral arterial circulation of the heart has been extensively studied. How- ever, less attention has been paid to extracardiac anastomoses, which may also be of significant clinical importance. In this review, we will describe the most common types of these anastomoses, which include bronchial to coronary arteries and internal thoracic to coronary arteries. In a much lesser degree, anastomoses between coronary arteries and pericardiacophrenic branches of the internal thoracic arteries, anterior mediastinal arteries, intercostal arteries, and esophageal arterial branches have also been described. Knowledge of the likely morphology and function of the anastomoses, therefore, could prove helpful in the clinical evaluation of patients with myocardial ischemia, particu- larly when selecting candidates for myocardial revascularization. Clin. Anat. 24:137–142, 2011. V V C 2010 Wiley-Liss, Inc. Key words: collateral circulation; extracardiac collateral circulation; circum- flex branch of the left coronary artery; coronary arteries; internal thoracic artery; bronchial artery INTRODUCTION The coronary arterial collateral circulation within the heart has been extensively studied (Anderson and Loukas, 2009; Schaper, 1971; Loukas et al., 2009). In the setting of severe coronary arterial atherosclero- sis, however, intercoronary arterial anastomoses may not always be able to satisfy the demand of the myo- cardium (Loukas et al., 2009). In such cases, the met- abolic demand of the myocardium requires an alter- nate supply through collateral coronary arteries, as previously described by Schaper (1971). There is still controversy regarding the nature, significance, and development of coronary arterial collateral circulation. There is also debate over the effectiveness of these anastomoses in maintaining the demands of myocar- dium, and prolonging life in patients with severe coro- nary arterial stenosis, compared with individuals who do not develop a collateral circulation (Harris et al., 1972; Helfant et al., 1970). There are two types of coronary collaterals arteries: the endomural forming anastomoses between the epicardial arteries and the extracardiac. The extracardiac coronary arterial anastomoses, however, have received little attention, albeit known to exist in the setting of multiple diseases, and hav- ing been demonstrated in normal individuals regard- less of their age (Moberg, 1967a). These extracar- diac anastomoses usually take origin either from the bronchial arteries, or from the internal thoracic arteries, the latter arrangement described by von Haller as long ago as 1803. As we will see, nonethe- less, anastomoses can also develop from other arteries adjacent to the heart. Although receiving attention from Hudson et al. (1931), it was Moberg (1967a) who provided the first detailed account of the extracardiac anastomoses, and it was he who suggested their potential physiological benefit. In this review, we emphasize their potential importance in the clinical setting. *Correspondence to: Marios Loukas, Department of Anatomical Sciences, St. George’s University, School of Medicine, Grenada, West Indies. E-mail: mloukas@sgu.edu Received 3 January 2010; Revised 10 August 2010; Accepted 27 September 2010 Published online 30 November 2010 in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/ca.21088 V V C 2010 Wiley-Liss, Inc. Clinical Anatomy 24:137–142 (2011)