Hospital Volume and 30-day Mortality following Hospitalization for Acute Myocardial Infarction and Heart Failure Joseph S. Ross, MD, MHS Mount Sinai School of Medicine James J. Peters VA Medical Center

Background For numerous surgical conditions and medical procedures, admission to higher volume hospitals has been associated with lower mortality rates. Strongest associations for cancer and AAA surgeries, more modest for PCI and CABG and orthopedic surgeries.

Background Fewer studies of medical conditions. Conceptually: –For surgeries and procedures  practice makes perfect –For medical care  less routinization; organizational structures and processes

Background Care for medical conditions is common and costly: –HF is most common admission, 2 nd most expensive for Medicare –AMI is 4 th most expensive for Medicare Drive to improve health care quality – is volume a marker?

Background Two studies focused on AMI treatment. –Farley & Ozminkowski (Medical Care, 1992) used HCUP data from , didn’t adjust for invasive capacity: 10% increase in hospital volume decreased mortality 2.2%. –Thiemann et al. (NEJM, 1999) used CCP data from , prior to key advances, but adjusted for invasive capacity: HR=1.17 ( ) [lowest quartile to highest quartile] No studies focused on HF treatment.

Research Objective To examine whether admission to a higher volume hospital is associated with lower mortality rates for AMI and HF.

Data Source Medicare Provider Analysis and Review (MEDPAR) claims data from all FFS beneficiaries hospitalized from in U.S. acute-care hospitals.

Study Population FFS patients hospitalized for AMI and HF identified using ICD-9-CM codes. Transfers linked into a single episode of care; outcomes attributed to index hospital. Excluded patients admitted to hospitals with 10 or fewer admissions, admissions <24hrs not AMA.

Main Outcome Measure 30-day risk-standardized all-cause mortality rates (RSMR).

Primary Independent Variable Hospitals were categorized by condition- specific volume quartile (prior to application of exclusion criteria): –Low (Q1+Q2) –Moderate (Q3) –High (Q4)

Statistical Analysis Weighted hierarchical model that included patient variables (1 st level) and hospital variables (2 nd level): –CABG surgery/PCI capacity –Teaching status –Ownership status

Results From : –801,307 AMI hospitalizations in 3,978 hospitals –1,245,564 HF hospitalizations in 4,328 hospitals Mean Condition-Specific Volume Hospital Volume LowModerateHigh AMI HF

% of Patient Hospitalizations Hospital Volume LowModerateHigh AMI4%19%77% HF5%22%73%

Patient Characteristics by Volume (For AMI)Hospital Volume LowModerateHigh Sociodemographics Age, Mean Female, % Past Medical History Prior MI, %12 14 Valvular heart disease, % Htn, % DM, % PVD, %151619

Hospital Characteristics by Volume (For AMI)Hospital Volume LowModerateHigh CABG surgery capacity, %21059 PCI capacity, %31757 COTH member, %1317 Teaching affiliate, %61344 Public ownership, %36179

Volume & Observed AMI Mortality

Volume & AMI RSMR Admission to both high and moderate volume hospitals was associated with lower AMI RSMRs when compared with low volume hospitals: –High: OR=0.82 ( ) –Moderate: OR=0.89 ( )

Volume & Observed HF Mortality

Volume & HF RSMR Admission to both high and moderate volume hospitals was associated with lower HF RSMRs when compared with low volume hospitals: –High: OR=0.85 ( ) –Moderate: OR=0.93 ( )

Conclusions Hospital volume was associated with lower risk-standardized odds of death after admission both AMI and HF among FFS Medicare beneficiaries. For high volume hospitals, 18% lower odds for AMI, 15% for HF.

Limitations Focused only on mortality, not other important dimensions of quality. –i.e., processes of care, patient experiences. May not be generalized to other conditions or to care provided in ambulatory settings. Observational study – can not rule out confounding of hospital volume by other unmeasured variables.

Implications A relationship between volume and outcomes may exist for some medical conditions, as well as for surgical conditions and procedures. Provides some reassurance as quality organizations begin to use volume as a surrogate for quality.

Study Team Yale University/Yale New-Haven Hospital Yun Wang, PhD Jersey Chen, MD Judith H. Lichtman, PhD, MPH Harlan M. Krumholz, MD, SM Entire CORE team Harvard University Sharon-Lise T. Normand, PhD Sunnybrook Health Sciences Centre Dennis T. Ko, MD, MSc