Key Insights On Assessing The Risk Factors For PAD
- Volume 21 - Issue 5 - May 2008
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Peripheral arterial disease (PAD) is a significant risk factor for diabetic foot amputation. It is also an important marker for atherosclerosis in other organ systems and is associated with a fourfold increase in cardiovascular death.1
Current estimates suggest a 3 to 10 percent incidence of PAD in the general population but reportedly only 25 to 33 percent of these people are symptomatic. Of the patients with asymptomatic PAD, 70 to 80 percent will remain stable at five years whereas 10 to 20 percent will experience significant deterioration of their health due to the disease.
Peripheral arterial disease is associated with traditional cardiovascular risk factors. In fact, the prevailing thinking is the biology of PAD may be similar to other manifestations of atherosclerotic disease. The two strongest risk factors for PAD are smoking and diabetes. Lesser factors include age, race, hypertension and dyslipidema.
Being able to assess the risk factors of PAD will allow the clinician to determine which patients would benefit most from screening and potential risk modifications.
Recognizing The Significant Risk Of PAD Among Smokers
Smoking has long been recognized as a significant risk factor for atherosclerotic disease. The exact mechanism of atherothrombosis is unclear and independent of its modification of other cardiovascular risk factors. Interestingly, smoking has a greater effect on PAD than coronary artery disease and is twice as likely to cause PAD. The overall risk of PAD for smokers is two to four times that of non-smokers.2 Furthermore, the effects of smoking are dose- and time-dependent with moderate smokers (< 25 pack years) twice as likely and heavier smokers (> 25 pack years) almost four times as likely to develop PAD.
Smoking is associated with continued progression of atherosclerosis and an increased risk for amputation.3 Observational studies have shown that smoking cessation decreases the risks of death and myocardial infarction, and amputation is substantially greater in those individuals with peripheral arterial disease. In one study, 82 percent of non-smokers had a 10-year survival rate in comparison to 46 percent in smokers.4 Unfortunately, there are no prospective randomized trials that have examined the effects of smoking cessation on lower extremity PAD. Nevertheless, researchers have associated smoking cessation with a decline in the incidence of PAD and it is an essential part of risk management.5
When Patients Have PAD And Diabetes
Peripheral arterial disease is four times more likely when diabetes is present. In fact, the incidence and extent of PAD is proportional to the duration and severity of diabetes.6 Diabetes changes the presentation of PAD as there tends to be more distal involvement and it is also more aggressive. Patients with PAD and diabetes are at greater risk for the development of critical limb ischemia, amputation and suffer from greater cardiovascular events.6
Metabolic abnormalities that accompany diabetes cause arterial dysfunction and promote thrombosis. Hyperglycemia, a cardinal presentation of diabetes, is correlated with an increased risk of PAD. Researchers have found this correlation in the diabetic population as well as the non-diabetic population. Researchers have linked a 1 percent increase in the percentage of HbA1c to a 28 percent increase in the incidence of PAD.7
The treatment of hyperglycemia has been a mainstay of diabetes and complications. Current guidelines from the American Diabetes Association (ADA) recommend HA1C < 7.0 percent in all patients with diabetes and PAD.8
While authors have shown that glycemic control reduces the risk of microvascular disease such as retinopathy and nephropathy, there is no significant evidence to date that demonstrates an effect on large vessel disease.9,10 This suggests that hyperglycemia alone is not responsible for the development of PAD. The metabolic syndrome accompanied with diabetes may play an important role in the development of PAD.