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Diabetic macrovascular complications result from changes in the medium to large blood vessels. Blood vessel walls thicken, scle-rose, and become occluded by plaque that adheres to the vessel walls. Eventually, blood flow is blocked. These atherosclerotic changes are indistinguishable from atherosclerotic changes in people without diabetes, but they tend to occur more often and at an earlier age in diabetes. Coronary artery disease, cerebrovas-cular disease, and peripheral vascular disease are the three main types of macrovascular complications that occur more frequently in the diabetic population.
Myocardial infarction is twice as common in diabetic men and three times as common in diabetic women. There is also an in-creased risk for complications resulting from myocardial in-farction and an increased likelihood of a second myocardial infarction. Coronary artery disease may account for 50% to 60% of all deaths in patients with diabetes. One unique feature of coronary artery disease in patients with diabetes is that the typi-cal ischemic symptoms may be absent. Thus, patients may not experience the early warning signs of decreased coronary blood flow and may have “silent” myocardial infarctions. These silent myocardial infarctions may be discovered only as changes on the electrocardiogram. This lack of ischemic symptoms may be sec-ondary to autonomic neuropathy (see below).
Cerebral blood vessels are similarly affected by accelerated ath-erosclerosis. Occlusive changes or the formation of an embolus elsewhere in the vasculature that lodges in a cerebral blood vessel can lead to transient ischemic attacks and strokes. People with di-abetes have twice the risk of developing cerebrovascular disease, and studies suggest there may be a greater likelihood of death from cerebrovascular disease in patients with diabetes. In addition, recovery from a stroke may be impaired in patients who have elevated blood glucose levels at the time of and immediately after a stroke. Because symptoms of cerebrovascular disease may be similar to symptoms of acute diabetic complications (HHNS or hypoglycemia), it is very important to rapidly assess the blood glucose level (and treat abnormal levels) in patients reporting these symptoms so that testing and treatment of cerebrovascular disease (stroke) can be initiated if indicated.
Atherosclerotic changes in the large blood vessels of the lower extremities are responsible for the increased incidence (two to three times higher than in nondiabetic people) of occlusive peripheral arterial disease in patients with diabetes. Signs and symptoms of peripheral vascular disease include diminished peripheral pulses and intermittent claudication (pain in the buttock, thigh, or calf during walking). The severe form of arterial occlusive disease in the lower extremities is largely responsible for the increased inci-dence of gangrene and subsequent amputation in diabetic pa-tients. Neuropathy and impairments in wound healing also play a role in diabetic foot disease.
Diabetes researchers continue to investigate the relation between diabetes and macrovascular diseases. The main feature unique to diabetes is an elevated blood glucose level; however, a direct link has not been found between hyperglycemia and atherosclerosis. Although it may be tempting to attribute the increased prevalence of macrovascular diseases to the increased prevalence of certain risk factors (eg, obesity, increased triglyceride levels, hyperten-sion) among patients with diabetes, there is a higher-than-expected rate of macrovascular diseases among patients with diabetes when compared with nondiabetic patients with the same risk factors (ADA, Management of Dyslipidemia in Adults With Diabetes, 2003). Thus, diabetes itself is seen as an independent risk factor for the development of accelerated atherosclerosis. Other potential factors that may play a role in diabetes-related atherosclerosis include platelet and clotting factor abnormalities, decreased flexibility of red blood cells, decreased oxygen release, changes in the arterial wall related to hyperglycemia, and possi-bly hyperinsulinemia.
Management of macrovascular complications involves preven-tion and treatment of the commonly accepted risk factors for ath-erosclerosis. Diet and exercise are important in managing obesity, hypertension, and hyperlipidemia. In addition, the use of med-ications to control hypertension and hyperlipidemia may be in-dicated. Smoking cessation is essential. Control of blood glucose levels may reduce triglyceride levels and can significantly reduce the incidence of complications.
When macrovascular complications do occur, treatment is the same as with nondiabetic patients. In addition, patients may re-quire increased amounts of insulin or may need to switch from oral antidiabetic agents to insulin during illnesses.
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