MI often unrecognized in patients with triple threat of diabetes, hypertension, and nephropathy

Susan Jeffrey

July 28, 2004

Houston, TX - A new study in a contemporary cohort shows a relatively high incidence of clinically unrecognized Q-wave MI among patients with diabetes, hypertension, and nephropathy[1]. Some 14% of first nonfatal MIs occurring among patients enrolled in the Irbesartan Diabetic Nephropathy Trial (IDNT) were identified only by protocol-driven electrocardiogram.

The study appears in the August 1, 2004 issue of the American Journal of Cardiology.

First author Dr David Aguilar (University of Texas Health Science Center, Houston) told heartwire that they were surprised by the number of unrecognized MIs in this clinical trial, where presumably both patients and physicians would be vigilant for cardiac events that were part of the primary end point.

"There are infarcts occurring that are escaping recognition, and we have to be aggressive in both counseling patients beforehand to try to prevent them and perhaps...having a low threshold for screening someone who has these risk factors and may have atypical symptoms," Aguilar said.

Diabetes patients at particular risk?

In the general population, the incidence of unrecognized MI has been estimated at between 20% and 40% by previous observational work, Aguilar said. Patients with type 2 diabetes are considered more susceptible to unrecognized MI, due perhaps to the neuropathy that can occur with the disease, interfering with their perception of pain, or because frequently their symptoms are atypical.

In this study, Aguilar and colleagues used data from IDNT, where serial ECGs were available, to determine the number of new Q-wave infarctions in this cohort. In the trial, 1387 patients underwent ECG at baseline and then at 6, 12, 24, 36, and 48 months. All tests were evaluated by a core laboratory.

During a mean follow-up of 2.5 years, 14 of 99 first nonfatal MIs, or 14%, identified by ECG were clinically unrecognized. Although this number is less than previous estimates in the general population, the researchers note, it is more than the 4.3% of events that went unrecognized in the Heart Estrogen/Progestin Replacement Study (HERS).

Based on the HERS findings, where the incidence of unrecognized MI was quite low, frequent screening might not be cost effective, he noted. However, their new findings suggest it's still an important clinical problem, although this study is probably too small to make reliable cost-effectiveness estimates.

"I don't know if we can draw large conclusions regarding [frequent screening], but I think it's something to consider and hopefully an area of further research," he said.

The researchers point out that these numbers do not include the occurrence of non-Q-wave MI, which would bring the total even higher.

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