The question of “how important collaterals are” is a rhetorical one. The essential value of collaterals is clearly demonstrated in patients with a completely preserved left ventricular function despite a totally occluded coronary artery. There is even the anecdotal argument that collaterals might be so well developed that the revascularisation of an occluded coronary artery might not be required, but clinical data suggest that revascularising a chronic coronary occlusion provides a survival benefit.^1,2 Furthermore, the quantitative assessment of collateral function demonstrated that <5% of occluded arteries in patients without a prior myocardial infarction receive collateral supply equivalent to an open epicardial artery.³

Recovery of functionally impaired myocardium after revascularisation can only be expected with a minimum collateral supply to maintain myocardial viability.⁴ In the absence of collaterals, no viable myocardium will be found,^5,6 but there is a dispute about whether the extent of collaterals is directly related to viability and the potential for functional recovery.^7,8 The history and circumstances of the development of …