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Studies examine effect of physician practice size and opening of specialty cardiac hospitals on treatment of heart attack patients

Clinical practice guidelines recommend early heart imaging (via cardiac catheterization) and reopening of blocked arteries (revascularization) by coronary artery bypass graft surgery (CABG) or coronary angioplasty for heart attack patients (acute myocardial infarction, or AMI).

Physicians in solo practices may be less likely than those in group practices to follow guidelines calling for quick use of cardiac imaging and angioplasty for Medicare patients, suggests a new study supported in part by the Agency for Healthcare Research and Quality (HS11114).

On the other hand, the opening of a specialized cardiac hospital in a region is associated with higher rates of coronary revascularization in Medicare patients, according to a second AHRQ-supported study (HS15571). Both studies are summarized here.

Ketcham, J.D., Baker, L.C., and MacIsaac, D. (2007, January). "Physician practice size and variations in treatments and outcomes: Evidence from Medicare patients with AMI." Health Affairs 26(1), pp. 195-205.

Physician practice size may be associated with care of hospitalized heart attack patients covered by traditional fee-for-service Medicare. Researchers found that patients of physicians in group practices had 10 to 12 percent higher rates of cardiac catheterization and 10 to 26 percent higher rates of angioplasty within one day of hospital admission than patients of solo-practice physicians in the same hospital. Patients of physicians in group practices also had lower mortality rates, even after accounting for patient and physician characteristics.

The research team used Medicare claims data on 116,671 heart attack patients to examine whether the practice size of attending physicians was related to within-hospital differences in their care. They used the Medicare Unique Physician Identification Number to link physician characteristics and practice size with individual patients. Overall, 39 percent of patients had an attending doctor from a solo practice, 16 percent from a practice of 2 to 5 physicians, 11 percent from a practice of 6 to 9, 10 percent from a practice of 10 to 19, 7 percent from a practice of 20 to 49, and 7 percent from a practice of 50 or more.

For the smallest three practice size categories, treatment rates increased and mortality rates decreased with greater practice sizes. However, these trends did not appear to continue among practices with 10 or more physicians. One explanation for the study results is that solo-practice physicians may not benefit from the ease of information sharing and consultation of group practices.

Nallamothu, B.K., Rogers, M.A., Chernew, M.E., and others (2007, March). "Opening of specialty cardiac hospitals and use of coronary revascularization in Medicare beneficiaries." Journal of the American Medical Association 297(9), pp. 962-968.

Specialty cardiac hospitals are opening at a rapid pace across the United States. This study found that the opening of a cardiac hospital within a hospital referral region (HRR) or health care market was associated with increasing population-based rates of coronary revascularization (i.e., bypass surgery or coronary angioplasty) in Medicare beneficiaries.

The opening of cardiac hospitals in the 13 HRRs studied between 1999 and 2003 was associated with an estimated 3,032 additional coronary revascularizations. Adjusted rates of change in revascularization were more than 2-fold higher in HRRs 4 years after cardiac hospitals opened (19.2 percent) than in HRRs where new cardiac programs opened at general hospitals (6.5 percent) and in HRRs with no new programs (7.4 percent).

The findings do raise some concern about the influence of physician ownership of cardiac hospitals on decisions about the use of coronary revascularization. For example, among heart attack patients, the subset of patients who are likely to gain the most from angioplasty, there was no association between the opening of a regional cardiac hospital and the rate of angioplasty. Growth in angioplasty rates were largely driven by its increased use for patients who had not suffered a heart attack, a group for whom the benefits of this procedure are often less clear.

Alternatively, these findings may reflect improved efficiencies in patient care that do not directly reflect financial incentives. The findings were based on calculation of annual population-based rates for CABG and angioplasty among Medicare beneficiaries from 1995 through 2003 in 13 HRRs.

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