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Complications of Diabetes Mellitus: Cardiac Complications

Diabetes mellitus (DM), both type 1 and type 2, affects many organ systems, particularly the heart, eyes, kidneys, and the peripheral and autonomic nervous systems. Also, macrosomia and birth complications occur more often in infants born to women with inadequately controlled diabetes mellitus.

Prevention of macrovascular complications depends on control of the major risk factors for cardiac disease, such as smoking, blood pressure, and blood lipid concentrations; blood glucose control has been less effective in controlled trials. For prevention of microvascular damage, glycemic control is essential, and control of blood pressure and other vascular parameters is also important.

1. Cardiac Complications1

Cardiovascular disease (CVD) is the leading cause of mortality in individuals with diabetes. Morbidity due to CVD is also common. Control of cardiac risk factors is therefore critical. These include smoking, hypertension, and hyperlipidemia (see chapters on CHD, hypertension, and hyperlipidemia ).

Risk Factors

Diagnosis

Patients with diabetes may have atypical presentations for CVD. Screening with electrocardiogram or cardiac stress tests may be appropriate in some patients.

Hypertension

Blood pressure control is particularly important for individuals with diabetes. The goal blood pressure should be less than 130/80 mmHg, and further lowering may be beneficial (see Hypertension ).

Hyperlipidemia

The goals for blood lipid concentrations are also somewhat different for patients with diabetes. LDL should be less than 100 mg/dl, and in certain patients (especially those with known CVD), the goal may be less than 70 mg/dl. In known cases of CVD, triglycerides should be less than 150, and HDL greater than 40 mg/dl. HDL greater than 50 mg/dl may be an appropriate goal for women (see Hyperlipidemia ).

Treatment

Dietary and behavioral modifications, including smoking cessation, regular exercise, and loss of excess weight, are critical for the prevention and management of cardiac complications in diabetes patients.

When further therapy is needed, specific medicines are usually helpful.

Aspirin therapy (75-325 mg/day) is recommended for most persons older than 30 years of age, particularly in the presence of additional cardiovascular risk factors or documented cardiovascular disease. Potential side effects, including bleeding, must be considered. Because of the risk of Reye's syndrome, aspirin therapy should not be instituted in patients under 21 years.

Hypertension

Hypertension in diabetes should be treated with an angiotensin-converting enzyme (ACE) inhibitor or angiotensin receptor blocker (ARB). Further drugs to lower blood pressure may be required. These include diuretics, beta blockers, and calcium channel blockers (see Hypertension).

Hyperlipidemia

Statins and fibrates are likely to be effective in reducing cardiovascular events, and other lipid-lowering therapies may also be tried in combination (see Hyperlipidemia ).

Nutritional Considerations

To reduce the risk of cardiac complications, the appropriate dietary changes are those that improve plasma lipid concentrations, reduce blood pressure, and control glycemia. These steps are discussed in detail in the chapters on coronary heart disease, hyperlipidemia, hypertension, and diabetes.

A substantial body of evidence suggests that a combination of a vegetarian diet, regular exercise, smoking cessation, and stress management yields greater improvements in indices of cardiovascular disease, compared with other regimens.2,3 The Multicenter Lifestyle Demonstration Project, which included 440 patients with coronary artery disease, of whom 91 also had diabetes, showed that such a regimen is effective in individuals with diabetes, just as it is for those without diabetes.4 In a randomized, controlled trial of individuals with type 2 diabetes, a low-fat, vegan diet reduced LDL cholesterol concentrations by 21% and reduced triglycerides by 16% among participants whose lipid-lowering medications were held constant.5 The type of carbohydrate that predominates in the therapeutic diet may be clinically important. Diets high in refined carbohydrate may increase triglyceride concentrations for some individuals, but high-carbohydrate diets that are drawn from high-fiber and low-glycemic index foods appear to have the opposite result.6

A randomized controlled clinical trial of alpha-lipoic acid, administered at 800 mg/d for 4 months, showed improvements in symptoms of cardiac autonomic neuropathy.7 Further study with a larger number of individuals is required before this treatment can be recommended.

 

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