The relationships among physician and hospital volume, processes, and outcomes of care for acute myocardial infarction.
BACKGROUND
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.


OBJECTIVE
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.


METHODS
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.


RESULTS
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.


CONCLUSIONS
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.
*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.
Yu-Chi
YC
Tung
Guann-Ming
GM
Chang
Kuo-Liong
KL
Chien
Yu-Kang
YK
Tu
D000319:Adrenergic beta-Antagonists / Q000008:administration & dosage; D000368:Aged; D015906:Angioplasty, Balloon, Coronary; D001241:Aspirin / Q000008:administration & dosage; D002423:Cause of Death; D001026:Coronary Artery Bypass; D005260:Female; D019983:Guideline Adherence; D006276:Health Facility Size; D017052:Hospital Mortality; D006801:Humans; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors / Q000008:administration & dosage; D033183:Interdisciplinary Communication; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000401:mortality / Q000628:therapy*; D009313:National Health Programs; D010043:Outcome and Process Assessment, Health Care; D010818:Practice Patterns, Physicians' / Q000706:statistics & numerical data*; D013624:Taiwan
D000319:Adrenergic beta-Antagonists; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D001241:Aspirin