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Cardiomyopathy

Damage to the structure and function of the heart caused by diabetes. It is extremely prevalent: In one study, 52% of people with Type 2 diabetes had some degree of diabetic cardiomyopathy.

To understand how diabetes affects the heart muscle, it is important to understand how the heart normally functions. The heart has four chambers: two on top called atria and two on the bottom called ventricles. During each heartbeat, the chambers contract in a synchronized fashion. First the atria contract to fill the ventricles with blood. Then the ventricles contract, sending blood into circulation, as the atria relax to fill with blood again.

For decades, doctors have noticed certain changes in the structure and function of the heart that take place in people with diabetes. One of the hallmarks of diabetic cardiomyopathy is left ventricle diastolic dysfunction, which is impairment in the way the left ventricle fills with blood between heartbeats, along with increased filling of the atria. People with Type 2 diabetes are more prone to having left ventricular hypertrophy, in which the left ventricle is enlarged. Left ventricular hypertrophy may be due to insulin resistance syndrome and could contribute to left ventricular diastolic dysfunction.

Another change seen in people with diabetes is myocardial fibrosis, which is scarring of the thick middle layer of the heart wall (the myocardium). Researchers believe that myocardial fibrosis may be due to high blood glucose levels, which in turn can promote glycation of, and damage to, certain proteins in the myocardium. Results of the Strong Heart Study showed that the extent and frequency of diastolic dysfunction was directly related to the glycosylated hemoglobin, or HbA1c, level (a measure of blood glucose control).

Since diabetic cardiomyopathy is now known to be prevalent even among people with Type 2 diabetes who have no symptoms of heart disease, some medical researchers are calling for more widespread screening for this condition. Doctors do not yet agree on the best screening methods for diabetic cardiomyopathy. Some researchers have suggested that since microalbuminuria (the appearance of small amounts of the protein albumin in the urine) has been shown to be proportional to diastolic dysfunction, a microalbuminuria test could be used as an initial screen for diabetic cardiomyopathy (it is already widely used to screen for diabetic kidney disease). Diabetic cardiomyopathy can be diagnosed definitively using various echocardiography techniques, which use reverberating sound waves to produce a moving image of the heart muscle in action.

A number of therapies can be used to prevent diabetic cardiomyopathy from progressing to heart failure (in which the heart cannot pump blood efficiently enough to meet the body’s needs). Good blood glucose control is essential, especially with medicines that decrease insulin resistance. Two classes of blood-pressure-lowering drugs may be helpful: Angiotensin-converting enzyme (ACE) inhibitors, which lower blood pressure by widening the blood vessels, may be used to decrease left ventricular hypertrophy and myocardial fibrosis. Beta-blockers, which alter the heartbeat to lower blood pressure, may also be used. Doctors sometimes prescribe drugs called aldosterone blockers to reduce myocardial fibrosis.

If you have Type 2 diabetes and have had a positive test for microalbuminuria, be sure to ask your doctor whether you should be tested for diabetic cardiomyopathy.



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