Diagnostic Studies

The history and physical examination generally facilitate classification of the degree of arterial insufficiency. Diagnostic studies are indicated when the diagnosis is in question, or in preparation for intervention. Noninvasive vascular testing is also useful in establishing the degree of ischemia when there are other confounding factors present, such as venous disease, diabetic foot ulcers, or active infection. Usually the ABI facilitates accurate determination of the degree of limb ischemia; however, several conditions exist in which the ABI and segmental pressures may be falsely elevated. These include diabetes, chronic renal failure, and advanced age (over 80 years), which can cause calcification of the medial layer of the arterial wall, which in turn causes incompressibility and subsequent false elevation of any cuff-based determination of peripheral perfusion pressure. An ABI of greater than 0.9 is associated with a readily palpable pulse, and the absence of a pulse with such an ABI value is evidence of incompressibility. In these cases several alternatives can be used to establish the diagnosis of arterial ischemia. A toe cuff can be used to determine a toe— brachial index (TBI), as the medial calcification rarely extends into the vessels of the foot. The waveform tracings from the pulse volume recorder are not altered by vessel calcification, and examination of the contour of these waveforms at the various arterial levels can suggest the site of the occlusive lesions. Flattened waveforms at the ankle or more distal level or a TBI less than 0.6 is an indication of arterial insufficiency. More sophisticated diagnostic measures such as transcutaneous oxygen measurement are sometimes useful to determine perfusion in the foot of patients with confounding factors such as lymphedema or severe venous insufficiency.

Exercise testing plays an important role in the subset of patients with symptoms of early occlusive disease despite relatively normal perfusion at rest. Increasing lower extremity blood flow by treadmill testing can accentuate the gradient across a moderate stenosis and demonstrate a drop in distal perfusion pressures after exercise that is not present at rest. This is based on


Poiseuille's law where the pressure drop across a stenosis is directly proportional to the volume flow across the lesion. Patients with a normal ABI at rest and a decreased ABI after exercise testing are uncommon and almost always have aortoiliac occlusive disease. Many patients cannot complete exercise testing on a treadmill because of angina or pulmonary dysfunction; however, a normal ABI after exercise testing excludes arterial insufficiency as a cause of lower extremity pain with walking.

Imaging studies of the aorta and lower extremity arteries are not necessary to determine the presence or extent of arterial insufficiency and are thus reserved for planning interventions to revascularize the lower extremity. The most widely used study is contrast angiography, although duplex scanning and magnetic resonance angiography are less invasive modalities that can provide images that can obviate the need for conventional angiography. These are utilized in patients with documented adverse reactions to contrast agents, or with renal insufficiency that increases their risk of contrast-induced nephropathy. In most patients, contrast angiography provides the most detailed information to direct catheter-based or surgical limb revascularization. Other imaging modalities that play a lesser role in the evaluation of limb ischemia include CT scans and ultrasound studies to determine the presence of aortic and peripheral aneurysms (especially as sources of emboli), echocardiography to evaluate potential cardiac embolic sources, and duplex evaluation of veins preoperatively for use as bypass conduits.

The Donts of Treadmill Buying

The Donts of Treadmill Buying

Though competitive runners are advised to run on the road, there are several reasons why you should buy treadmills anyway. You might have a family which means that your schedule does not have the flexibility it once had.

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