A volume-outcome relationship has been found for acute myocardial infarction (AMI); however, the mechanisms underlying the relationship remain unclear. In particular, it is not known whether processes of care are mediators of the volume-outcome relationship, that is, whether the mechanisms underlying the relationship are through processes of care.
We used nationwide population-based data to examine the mediating effects of processes of care on the relationships of physician and hospital volume with AMI mortality.
We analyzed all 6838 ST-elevation myocardial infarction (STEMI) patients admitted in 2008, treated by 740 physicians in 142 hospitals through Taiwan’s National Health Insurance Research Database. Multilevel meditational models were performed after adjustment for patient, physician, and hospital characteristics to test the relationships among physician and hospital volume, processes of care, and 30-day STEMI mortality.
Physicians with higher volume had higher use of percutaneous coronary intervention and aspirin, and lower mortality in the following year, and the processes of care were mediators of the relationship between physician volume and mortality. Low-volume hospitals had higher mortality in the following year than medium-volume hospitals. In stratified analyses the relationships only existed in nonlarge hospitals.
Physicians with high volume perform better on certain processes of care than those with medium and low volume, and have better outcomes for patients with AMI. The processes of care could partly explain the relationship between physician volume and AMI mortality. However, the relationships existed in nonlarge hospitals but not in large hospitals.
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*Institute of Health Policy and Management, National Taiwan University, Taipei
†Department of Family Medicine, Cardinal Tien Hospital
‡School of Medicine, Fu Jen Catholic University, New Taipei City
§Institute of Epidemiology and Preventive Medicine
∥Department of Internal Medicine
¶Institute of Epidemiology and Preventive Medicine, National Taiwan University, Taipei, Taiwan
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The study is supported by Grants from the National Science Council (NSC99-2410-H-130-005) in Taiwan, and is based in part on data from the National Health Insurance Research Database provided by the National Health Insurance Administration and managed by National Health Research Institutes. The interpretation and conclusions contained herein do not represent those of National Health Insurance Administration or National Health Research Institutes.
The authors declare no conflict of interest.
Reprints: Yu-Chi Tung, PhD, Institute of Health Policy and Management, National Taiwan University, Room 634, No.17, Xu-Zhou Road, Taipei 100, Taiwan. E-mail: firstname.lastname@example.org.