Study: Higher-Volume Hospitals Have Lower Mortality Rates in Three Conditions

Higher-volume hospitals saw lower mortality for acute myocardial infarction, heart failure, and pneumonia, according to a new study in the New England Journal of Medicine.

The study, led by Joseph S. Ross, MD, with the Mount Sinai School of Medicine in New York, analyzed data from Medicare claims for all fee-for-service patients, who were hospitalized between 2004 and 2006 in acute care hospitals for the three ailments.

"Hospital volume may be a sensible surrogate for quality in deciding where to obtain surgical and interventional care, but may not be similarly sensible for acute medical care. Understanding the relationship between hospital volume and mortality for medical conditions is critical for clinicians and policymakers, since they are under increasing pressure to identify strategies to improve the quality of care," the study said. "In addition, because three of the most common and costly reasons for hospital admission among Medicare beneficiaries are acute myocardial infarction, heart failure, and pneumonia, identifying factors associated with better quality of care has great significance."

The study examined 734,972 hospitalizations for acute myocardial infarction in 4,128 hospitals, 1,324,287 for heart failure in 4,679 hospitals, and 1,418,252 for pneumonia in 4,673 hospitals. An increased hospital volume was associated with reduced 30-day mortality for all conditions. For each condition, the association between volume and outcome was attenuated as the hospital's volume increased.

The study estimated the change in the odds of death within 30 days associated with an increase of 100 patients in the annual hospital volume. Analyses were adjusted for patients' risk factors and hospital characteristics.

For acute myocardial infarction, once the annual volume reached 610 patients (95% confidence interval [CI], 539 to 679), an increase in the hospital volume by 100 patients was no longer significantly associated with reduced odds of death. The volume threshold was 500 patients (95% CI, 433 to 566) for heart failure, and 210 patients (95% CI, 142 to 284) for pneumonia.