Collateral vessel physiology and functional impact–in vivo assessment of collateral channels

The existence and recruitment of collateral vessels within the coronary circulation may account for the tremendous variability in presentation, symptoms and outcome in patients with coronary atherosclerosis. Multiple episodes of ischemia have been found to produce the stimuli necessary for the growth of new vessels which result in collateral blood flow. Furthermore, there is also a subset of patients with readily recruitable collateral vessels that function to limit myocardial necrosis during an acute ischemic event. Promising early studies have utilized angiogenic growth factors as a means to stimulate collateral growth, bringing a renewal interest in their assessment and significance. We review, in brief, the significance and understanding of the development of coronary collaterals as well as the available means to assess them.