Heart Disease

Variation in use of coronary angiography after heart attack may reflect use in patients who don't need it

Use of coronary angiography to diagnose heart problems in heart attack patients varies substantially across geographic regions. The source of these differences apparently is not overuse of the procedure in some regions (use for patients who clearly don't need it) or underuse (non-use for patients whose clinical criteria warrant its use) in others. Rather, regional variations in use of the procedure are due primarily to its use in patients for whom angiography is judged either appropriate but not necessary or uncertain.

It is these gray areas that prompt varied clinical decisions that cannot easily be judged as appropriate or inappropriate care. Minimizing geographic variation in use of this procedure depends on better defining care for patients with discretionary indications, concludes Edward Guadagnoli, Ph.D., of Harvard Medical School.

In a study supported by the Agency for Healthcare Research and Quality (HS08071), Dr. Guadagnoli and colleagues used statistical models to estimate the true underlying rate of angiography for 95 hospital referral regions and measured the degree of variability within each appropriateness category (necessary; appropriate, but not necessary; uncertain; and unsuitable) by calculating the difference between the high and low rates for all regions. Criteria for suitability for the procedure included factors such as duration of symptom onset, patient age, use of clot-busting (thrombolytic) therapy, and presence of a complication such as shock or chest pain.

The difference between high and low angiography use rates across regions was only 16.3 percent for patients identified as clearly unsuitable for the procedure. The greatest variation in use was for patients with indications judged appropriate but not necessary or uncertain. When the researchers accounted for regional variation associated with these indications, the difference between the high and low overall rates decreased from 33 percent to 11 percent. In contrast, variation in the overall rate remained high when researchers accounted for underuse in necessary situations and overuse in unsuitable situations.

More details are in "Impact of underuse, overuse, and discretionary use on geographic variation in the use of coronary angiography after acute myocardial infarction," by Dr. Guadagnoli, Mary Beth Landrum, Ph.D., Sharon-Lise T. Normand, Ph.D., and others, in the May 2001 Medical Care 39(5), pp. 446-458.

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