NEJM: Higher volume hospitals mostly have less mortality with MI, heart failure

Admission to higher-volume hospitals was associated with a reduction in mortality for acute MI and heart failure, although there was a volume threshold above which an increased condition-specific hospital volume was no longer significantly associated with reduced mortality, based on study findings published March 25 in the New England Journal of Medicine.

Prior to this study, Joseph S. Ross, MD, from Mount Sinai School of Medicine in New York City, and colleagues noted that it was unknown whether a volume threshold was associated with lower death rates in patients with conditions who are often hospitalized.

The researchers conducted cross-sectional analyses of data from Medicare administrative claims for all fee-for-service beneficiaries who were hospitalized between 2004 and 2006 in U.S. acute-care hospitals for acute MI, heart failure and pneumonia. Using hierarchical logistic-regression models for each condition, they estimated the change in the odds of death within 30 days associated with an increase of 100 patients in the annual hospital volume.

According to the authors, there were approximately 735,000 hospitalizations for acute MI in 4,128 hospitals, 1.32 million for heart failure and 1.42 million for pneumonia. They found that an increased hospital volume was associated with reduced 30-day mortality for all conditions.

For each condition, Ross and colleagues found that the association between volume and outcome was attenuated as the hospital’s volume increased. For acute MI, once the annual volume reached 610 patients, an increase in the hospital’s volume by 100 patients was no longer significantly associated with reduced odds of death. Likewise, the volume threshold was 500 patients for heart failure.

The researchers noted that “hospital volume was independent of certain hospital characteristics, including teaching status and capacity to provide cardiovascular revascularization services. Nevertheless, although volume thresholds differed according to the type of hospital, the attenuating association was consistently observed.”

The authors wrote that their findings have “two clear policy implications:”

• Policymakers may suggest that acute care be regionalized so that patients requiring hospitalization for acute MI or heart failure are transferred to receive care at "above threshold" hospitals, or at least those hospitals on the flattening part of the volume-mortality curve.
• Policymakers may attempt to increase volume at only the smallest-volume hospitals, perhaps by ensuring that small hospitals are not located within close proximity to one another, which could be accomplished through state certificate-of-need regulations or critical-access hospital programs.