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Patient characteristics, procedure volume account for lower mortality rates at cardiac specialty hospitals relative to noncardiac hospitals, research suggests

Wednesday, May 02 2012 | Comments
Evidence Grade 0 What's This?
Although a recently published study shows that the risk-adjusted mortality rate was significantly lower for patients who underwent percutaneous coronary intervention (PCI) at any of six cardiac specialty hospitals in Texas as compared with the state average for this procedure, the authors of the study found that generally healthier patients and higher procedure volume at the specialty hospitals accounted for much of the difference between the specialty hospitals and noncardiac facilities.

Using hospital inpatient data from the Texas Department of State Health Services, the researchers identified all patients who underwent PCI from 2004 though 2007 at any of six cardiac specialty hospitals or 18 general hospitals located in six of the state's major metropolitan markets.

Specialty hospitals were defined as those for which cardiac discharges made up at least 45 percent of total discharges. One of the cardiac hospitals opened during the last year of the study, so only 1.5 percent of the cases included in the analysis were performed at that facility. Five of the six cardiac hospitals were partly physician-owned.

The noncardiac hospitals were community facilities that admitted patients of cardiologists who also performed PCIs at cardiac hospitals.

Two comparisons were conducted--one at the hospital level, which included all inpatient PCIs performed during the study period (n=210,135), and one at the physician level, which included 48,460 PCIs performed by 47 specialty physicians (those who performed at least half of their procedures at a physician-owned cardiac hospital).

The intent was to examine whether a difference existed between the patients who were referred to the cardiac hospitals versus those who underwent PCI at the noncardiac hospitals, and to see if patient outcomes varied when the same physicians performed the same procedure at cardiac versus noncardiac hospitals.

According to the study authors, proponents of specialty cardiac hospitals contend that lower mortality rates observed at these facilities are partially attributable to physicians who are more highly skilled at delivering cardiac care. The authors said if this is true, then those same physicians should have above-average outcomes when performing the same procedures at nonspecialty hospitals. If, however, patient selection at cardiac hospitals is a major factor in the lower mortality rates, then the physicians who use the cardiac hospitals would be expected to have poorer outcomes when using a noncardiac facility.

Data for the hospital-level analysis showed that the cardiac hospitals treated significantly fewer patients of minority groups than the noncardiac hospitals did, as well as fewer uninsured patients and Medicaid enrollees. The specialty hospitals also had a significantly shorter average length of stay, significantly fewer emergency admissions and significantly more physician referrals as compared with the noncardiac hospitals.

Being a black or Hispanic patient, having no insurance or Medicaid coverage and being enrolled in a health maintenance organization plan significantly reduced the likelihood of being admitted to a cardiac facility rather than a noncardiac facility. Having commercial or private health insurance increased the likelihood of being treated at a cardiac facility rather than a noncardiac hospital.

The risk-adjusted mortality rate was significantly lower for the cardiac hospitals (0.9 percent) than for the for-profit noncardiac hospitals (1.9 percent) and the not-for-profit noncardiac hospitals (1.5 percent).

The overall volume of PCIs performed at the cardiac hospitals was considerably higher than the volume performed at the noncardiac hospitals. Four of the six cardiac hospitals did a minimum of 960 PCI procedures per year, which was more than double the average volume performed at the noncardiac facilities.

The physician-level analysis showed that during the entire study period, the 47 specialty physicians did an average of 314 PCIs at the cardiac hospitals, 12 PCIs at the for-profit noncardiac hospitals and 70 PCIs at the not-for-profit noncardiac hospitals.

The risk-adjusted mortality rates differed for patients of the specialty physicians depending on where the procedure was performed. For PCIs the specialty physicians performed at the cardiac facilities, the mortality rate was significantly lower than the state average (0.7 percent vs. 1.5 percent), whereas for PCIs done at the noncardiac hospitals, the rate was significantly higher than the state average (2.3 percent).

The researchers remarked that after adjusting for the severity of the patient's condition and physician caseload, the overall risk-adjusted mortality rate for the specialty physicians was not significantly different from that for other high-volume cardiologists in the state (1.3 vs. 1.4, respectively). Hence, they concluded that lower patient acuity and higher procedural volumes at the cardiac hospitals likely contributed to the better outcomes at those facilities relative to the noncardiac hospitals.

When the cardiologists were categorized according to what percentage of PCIs they performed at a cardiac hospital (range, 20 percent to 95 percent), the hospital-physician interaction effect was significant for all categories, being strongest for physicians who performed at least 90 percent of their PCIs at a cardiac hospital and weakest for those who performed fewer than half of their PCIs at a cardiac hospital.

"To remove a potential source of bias and achieve a more balanced comparison, the quality statistics reported by physician-owned cardiac hospitals should be adjusted to incorporate the high rates of poor outcomes for the many procedures done by their cardiologists at nearby noncardiac hospitals," the study authors recommended, adding that future studies should assess risk-adjusted mortality rates of physician-owned specialty hospitals for a longer period of time.

The study was published in the April issue of the journal Health Affairs.

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