Hospitals with high ICU admission rates for acute MI, heart failure may have high 30-day mortality rates, too

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A retrospective cohort study of Medicare beneficiaries found that hospitals with the highest rates of intensive care unit (ICU) admissions for acute MI or heart failure had the highest 30-day mortality rates.

However, those same hospitals did not have higher 30-day readmission rates or Medicare spending compared with hospitals with fewer ICU admissions.

Lead researcher Thomas Valley, MD, MSc, of the University of Michigan, and colleagues published their findings online in CHEST on June 15.

In 2011, cardiovascular conditions such as acute MI and heart failure accounted for 1.6 million hospitalizations and $1.6 billion, according to the researchers. They added that 20 percent of patients hospitalized with cardiac conditions do not receive standards of care, although the reasons are not fully known.

For this study, the researchers hypothesized that the quality of care variation may be attributed to the location in the hospital where patients receive care. They examined all Medicare beneficiaries hospitalized for acute MI or heart failure in 2010 and divided hospitals into quintiles based on their risk- and reliability-adjusted ICU admission rates. They excluded patients who transferred from another hospital, were discharged against medical advice or were admitted to hospitals without ICUs or hospitals with fewer than 25 acute MI or heart failure admissions.

Of the 157,033 patients who were hospitalized for acute MI, 46 percent received care in an ICU. Meanwhile, 16 percent of patients hospitalized for heart failure received care in an ICU.

After adjusting for risk and reliability, the median hospital ICU admission rate was 41.9 percent for acute MI and 11.3 percent for heart failure. Hospitals with the highest ICU admission rates tended to have a lower volume of hospital admissions for acute MI or heart failure. The researchers found there was no relationship between hospital size and ICU bed ratio.

Hospitals with higher ICU admission rates more often failed to deliver aspirin when patients arrived at the hospital with acute MI and provide ACE or ARB inhibitors to treat left ventricular systolic dysfunction.

After adjusting for patient and hospital characteristics, the 30-day mortality rates significantly increased in for hospitals in the highest quintiles of ICU admission rates for acute MI and heart failure. Hospitals in the lowest quintile had ICU admission rates of less than 29 percent for acute MI or less than eight percent for heart failure, while hospitals in the highest quintile had rates greater than 61 percent for acute MI and greater than 24 percent for heart failure.

For acute MI, the 30-day mortality rates ranged from 14.0 percent to 14.8 percent, while the 30-day readmission rates ranged from 16.7 percent to 17.0 percent and the Medicare spending ranged from $13,324 to $13,638 per patient.

For heart failure, the 30-day mortality rates ranged from 10.6 percent to 11.4 percent, while the 30-day readmission rates ranged from 22.0 percent to 22.8 percent and the Medicare spending ranged from $8,389 to $8,703 per patient.

The researchers cited a few potential limitations of the study, including that they may have improperly identified patients with acute MI or heart failure. They also used administrative claims when adjusting for risk, which may have introduced bias. In addition, they did not have information on the time between when patients were admitted to the hospital and to the ICU. Further, they evaluated the quality of care in the hospital as a whole and did not break it down by the areas of the hospitals such as the ICU or critical care unit.

“Our study has important implications for clinicians and health policy makers,” the researchers wrote. “The association between higher ICU admission rates and worse quality of care for patients with [acute MI or heart failure] suggests that additional work is needed to identify the mechanisms that link ICU admission with quality of care. By identifying hospitals that provide worse quality of care to patients, more resources may be devoted to recognizing gaps and enhancing care. This study underscores the need to understand the reasons why hospitals use the ICU, independent of a patient’s severity of illness, in order to improve quality of care.”