Diabetic patients with PAD have several distinct features when compared with non-diabetic patients with PAD. A greater proportion of diabetic patients with PAD have concomitant hypertension (152). In addition, diabetic patients have more distal disease, (152,153) more progressive and severe disease, and they are more likely to undergo surgery and amputation for critical limb ischemia (148,152,153). The rates of gangrene or amputation of lower limbs are as much as 10 to 20 times more frequent in diabetic than in control subjects (154,155). The risk of amputation also increases with age. The annual amputation rates were 14 per 10,000 in patients less than forty-five years of age, 45 per 10,000 in diabetics between age forty-five and sixty-four, and 101 per 10,000 in those over sixty-five. Not surprisingly, duration of diabetes has been found to be a strong risk factor for amputation (155). Interestingly, the type of vessels affected may vary compared with non-diabetic patients with PAD; recent evidence suggests that diabetes was the only significant risk factor for small vessel PAD progression, whereas smoking, dyslipidemia and elevated CRP level, were risk factors for large vessel PAD progression (156).
The risks of fatal and non-fatal MI and stroke are also increased in both diabetic and non-diabetic PAD subjects (148,152,155,157) Cirqui et al., found vascular mortality was five times higher in patients with claudication over a period of ten years, while another group reported an annual rate of fatal and non-fatal cardiovascular events ranging from 3.5 to 8% per year (158,159). One study found that 67% of diabetic patients dying from cardiovascular causes within the five-year observation had PAD at baseline, compared with 15% in those who survived (160). Therefore, diabetic patients with claudication are at high risk of future stroke, MI and premature death.
All diabetic patients should be screened for peripheral vascular disease including components targeted toward detection of signs and symptoms in the routine history and physical exam. In a workshop examining PAD in diabetes, the American Diabetes Association and American Heart Association made the following joint recommendations for annual screening (161). The history should include questions about the presence and degree of claudication or ischemic rest pain. The physical exam should include inspection of the legs and feet for ulcers and skin changes. The tibialis posterior and the dorsalis pedis pulses should be examined and the femoral pulse auscultated for bruits.
Diabetic patients should be asked annually about the presence of exercise-induced calf leg pain. Although the most common site for exercise-induced pain is the calf, it can also develop in the thigh, hip, or buttock when the disease is localized above the inguinal ligament. Often the pain will start in the calf and then progress to the thigh and/or buttock if exercise is continued despite the onset of pain. The Rose intermittent claudication questionnaire, allowed for standardization of many of these features of claudication (162). A typical history of claudication has low sensitivity, but a high specificity for PAD (163,164). A large scale PAD screening study has demonstrated that only one-third of patients with documented PAD had classic claudication symptoms. The remainder patients had either atypical symptoms or no symptom (163,164). Therefore, a thorough physical examination should include blood pressure measurement, palpation of peripheral pulses, and auscultation of pulses and bruits. Severe claudication most often results from multilevel arterial disease, which can be evaluated in the noninvasive laboratory. Patients with lifestyle limiting exercise-induced calf pain should be referred for specialist vascular assessment. Measurement of an Ankle brachial index (ABI) or referral for specialist vascular assessment should also be considered for patients with any leg pain not clearly ascribed to a nonvascular cause.
Critical ischemia is defined as clinical presentation that is likely to result in an amputation if not reversed. Ischemic rest pain occurs in the toes and forefoot will be relieved by dependency during its early phases. If it does not improve with development of collateral circulation, amputation will be necessary unless some form of intervention, either surgical or endovascular, is performed. When a break in the skin occurs at any location of the foot or lower leg, healing of the ulceration may not occur unless some form of intervention is carried out. When tissue death involves one or more toes or the forefoot, the extent of the amputation may be limited to the involved areas if direct intervention can bring more blood to the ischemic area. Although not as definitive as ischemic rest pain, ulceration and gangrene, skin atrophy, nail changes, and dependent rubor in some patients may require further evaluation. This is particularly true if the ABI is found to be abnormal.
Palpation of leg pulses should be performed on an annual basis for all adult patients with diabetes. Palpation of peripheral pulses should include an assessment of femoral, popliteal and pedal vessels. Pulse should be graded as absent, diminished or normal. Dorsalis pedis pulse abnormalities are less sensitive for PAD, since up to 30% of these abnormalities may be due to a congenital absence of the dorsalis pedis artery (165). An absent or decreased tibialis posterior pulse is an indication for performing an ABI. Since the sensitivity and positive predictive value are moderate for detection, a significant number of cases will be identified by detection of a reduction or absence of these pulses. The presence of these pulses in low-risk diabetic subjects helps to confirm the absence of significant disease.
The detection of femoral bruits is an indication for performing an ABI. Although auscultation for femoral bruits has similar difficulties to those described for pulse palpation, it nonetheless has sufficient sensitivity to merit annual performance.
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