Collateral vessels reduce mortality

This editorial refers to ‘The impact of the coronary collateral circulation on mortality: a meta-analysis’†, by P. Meier et al., on page 614 Christian Seiler, Pascal Meier, and their co-workers of the University Hospital in Bern, Switzerland, well known for their pioneering clinical work on the collateral circulation of the heart, have described a meta-analysis of 12 studies involving 6529 patients of the role played by the collateral circulation in mortality.1 The authors come to the conclusion that the ‘coronary collateralization has a relevant protective effect’. Mortality is reduced by 36% in patients with, compared with those without, demonstrable collaterals. This is a very important statement about a situation that most cardiologists believed that they knew from anecdotal evidence: patients with all three epicardial arteries occluded but without infarctions, in some cases even without typical ischaemic symptoms, die from an unrelated cause and with the post-mortem finding of long-standing major coronary artery disease, again without sign of infarction.2–4 However, the relevance of such observations was sometimes disputed: since collaterals develop in response to arterial stenoses and occlusions, it is quite clear that more collaterals can often be demonstrated in hearts with more advanced coronary artery disease, and indeed the conclusion was put forward that collaterals are the harbingers of a worsening course of the disease. Only a few but prominent clinicians5,6 clung to this view, but this is now roundly refuted.