Cardiovascular diseases, in particular coronary artery disease (CAD), are the leading cause of death in industrialised countries. Established options for revascularisation include angioplasty and surgical bypass, both of which are not suitable in 20–30% of patients in whom the extent of coronary atherosclerosis is especially severe. An alternative treatment strategy for revascularisation is therefore warranted both to control symptoms as well as to alter the course of advanced CAD. An ideal candidate to fill in this gap is therapeutic promotion of coronary collateral growth—that is, the induction of natural bypasses. In order to reach this goal, a comprehensive understanding of the human coronary collateral circulation with regard to its relevance, accurate assessment, the pathogenetic and pathophysiological aspects, and the different therapeutic options is mandatory.

RELEVANCE OF THE CORONARY COLLATERAL CIRCULATION

The coronary collateral circulation has been recognised for a long time as an alternative source of blood supply to a myocardial area jeopardised by ischaemia. More than 200 years ago, Heberden described a patient who had been nearly cured of his angina pectoris by sawing wood each day,^w1 a phenomenon called “warm up” or “first effort angina” which was traditionally ascribed to coronary vasodilation with opening of collateral vessels to support the ischaemic myocardium. Alternatively, and more recently, “walk through angina” has been interpreted as a biochemical (that is, ischaemic preconditioning) rather than a biophysical (that is, collateral recruitment) event leading to heightened tolerance against myocardial ischaemia. Both mechanisms probably contribute to the described phenomenon, which is easily obtainable by careful history taking of the patient.¹ Aside from the controversies just alluded to, there have been numerous investigations demonstrating a protective role of well versus poorly grown collateral arteries (fig 1) showing smaller infarcts,^w2 less ventricular aneurysm formation, improved ventricular function,^w2 fewer future cardiovascular events,² and improved survival.³