Detection of Ischemia in Patients with Asymptomatic Diabetics

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Citation
US Cardiology, 2006;3(1):16-20

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Individuals with both type 1 and type 2 diabetes mellitus (DM) are known to be at high risk for developing coronary artery disease (CAD). The risk is two to three times greater in those with DM compared with those without, and is especially high in women with DM. An additional problem in individuals with DM is that, even with severe underlying CAD, many individuals may have atypical symptoms or be totally asymptomatic, a condition referred to as silent or asymptomatic myocardial ischemia.

Asymptomatic myocardial ischemia is frequently found in individuals with known CAD, even in individuals without DM, and is associated with a poorer long-term prognosis. The Asymptomatic Cardiac Ischemia Pilot Study demonstrated that asymptomatic ischemia was associated with three times the risk of nonfatal myocardial infarction and six times the risk of myocardial infarction or death.1 However, asymptomatic myocardial infarction also occurs in a substantial number of individuals without known CAD, particularly those with DM. These individuals have not been diagnosed with CAD and do not have the benefit of anti-anginal therapies or aggressive CAD risk reduction. In the recent Detection of Ischemia in Asymptomatic Diabetics (DIAD) study, 21.6% of older adults with type 2 DM, none of whom had any clinical evidence of CAD, had evidence of myocardial ischemia on single photon emission computed tomography (SPECT) myocardial perfusion imaging.2 This finding was consistent with earlier studies in the population with type 2 DM.3

In asymptomatic patients with either type 1 or type 2 DM, asymptomatic myocardial ischemia is also associated with major cardiac events.4 Importantly, the presence of cardiac autonomic neuropathy, long theorized to have a role in asymptomatic CAD, substantially increases the risk of subsequent cardiac events, with those individuals with both asymptomatic myocardial ischemia and cardiac autonomic neuropathy, being at highest risk.5

MechanismsÔÇöA Role For Cardiac Autonomic Neuropathy ?

Asymptomatic myocardial ischemia is often associated with cardiovascular autonomic neuropathy (CAN). This type of neuropathy affects the parasympathetic and sympathetic innervation of the heart and peripheral vasculature. It is frequently found in many individuals with DM, even at the time of initial DM diagnosis. The presence of CAN confers a greater risk of death.

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References
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