Chronic Arterial Occlusion
Chronic arterial insufficiency is most often secondary to long-standing
atherosclerosis in which the arterial lumen of the lower extremity becomes progressively
stenosed by atherosclerotic plaque. When the stenosis approaches total occlusion,
the marked reduction in blood flow leads to thrombotic occlusion. Hemodynamically
significant stenosis and total vessel occlusion commonly exist in the lower extremity
with no or very minimal symptoms. The development of collateral vessels around a
stenosed or occluded arterial segment often prevents clinical symptoms until multiple
occlusions exist in major vessels. Most patients with peripheral arterial disease
are asymptomatic.[473]
[475]
[484]
Patients with symptoms most commonly present
with mild intermittent claudication—pain or fatigue in the muscles of the lower
extremity caused by exertion and relieved with rest. The pain usually occurs in
the muscle group distal to the site of arterial insufficiency. With disease progression,
patients can develop severe disabling intermittent claudication or rest pain, so-called
critical limb ischemia.
Noninvasive testing with the ankle-brachial index (ABI) is the
clinical standard for documenting the presence and severity of peripheral arterial
disease. The ABI is determined by dividing the ankle systolic pressure by the brachial
systolic pressure. Normally, ABI is between 1.0 and 1.1; a value less than 0.9 indicates
arterial disease proximal to the point of measurement. The ABI approximates the
degree of arterial insufficiency; claudication occurs with indices ranging from 0.3
to 0.9, disabling claudication or rest pain with indices less than 0.5, and gangrenous
extremities with indices less than 0.2.[492]
One of the most important aspects of peripheral arterial disease
is that it is a very strong marker for early mortality. In patients with peripheral
arterial disease, the risk of amputation is much less than the risk of death.[493]
A low ABI is a strong predictor for disease progression,[494]
[495]
but it is also one of the strongest risk factors
for all-cause mortality.[484]
Claudication is associated
with a high rate of mortality,[483]
but it is relatively
benign in terms of lower extremity outcome.[484]
[494]
