Expression of VEGF-A has been found to be induced by myocardial ischemia and a higher level of expression of VEGF-A has been associated with better collateral circulation development during ischemia.
22.
A golden rule is that there has to be collateral circulation to the area affected by the chosen artery, so that peripheral circulation is maintained by another artery even if circulation is disturbed in the cannulated artery.
23.
They participate in the formation of the periarticular genicular anastomosis, a network of vessels surrounding the knee that provides collateral circulation capable of maintaining blood supply to the leg during full knee flexion, which may kink the popliteal artery.
24.
"' Collateral circulation "'is the alternate engineered redundancy ), as in the circle of Willis in the brain, or it may occur via new branches formed between adjacent blood vessels ( neovascularization ), as in the eye after a retinal embolism.
25.
As smaller pulmonary emboli tend to lodge in more peripheral areas without collateral circulation they are more likely to cause lung infarction and small effusions ( both of which are painful ), but not hypoxia, dyspnea or hemodynamic instability such as tachycardia.
26.
Whether angina causes collateral development is still debatable, but at least one investigator, Fujita, believes that angina is either symptomatic of, or somehow promotes the development of, collateral circulation, and, in any case, sometimes precedes, and often prevents, infarction by relieving the critically occluded vessel before thrombosis can occur.
