Chronic damage to the inner lining of the blood vessels (intima) may give rise to small lesions, on which lipids, carbohydrates, calcium deposits and fibrinous plaques build up which later calcify and thus constrict the lumen. Increased accumulations of platelets occur at these points, the coagulation cascade is activated and thrombi may form which can lead to complete occlusions.
However, the body’s own compensation mechanisms ensure that PAD has a long interval with few symptoms, if any at all: only when the constriction occupies more than half the diameter of the vessel the resting blood supply reduces. The formation of collateral blood vessels to bridge the stenosis is also induced. Moreover, more oxygen is extracted in the regions with reduced blood supply (Bohr effect).