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Evolution of the volume-outcome relation for hospitals performing coronary angioplasty
V Ho1
1John M. Olin School of Business, Washington University, St Louis, MO 63130-4899, USA. ho@olin.wustl.edu
Insights
Hospital procedure volume impacts patient outcomes. This study shows outcomes improved for all hospitals over time, narrowing the gap between low- and high-volume centers for percutaneous transluminal coronary angioplasty (PTCA).
Area of Science:
- Cardiovascular Surgery
- Health Services Research
- Medical Quality Improvement
Background:
- Higher surgical procedure volumes in hospitals are generally associated with better patient outcomes.
- This study investigates the historical trends of the volume-outcome relationship in healthcare.
Purpose of the Study:
- To examine the evolution of the volume-outcome relationship for percutaneous transluminal coronary angioplasty (PTCA) procedures over time.
- To assess changes in in-hospital mortality and bypass surgery rates based on hospital PTCA volume across different time periods.
Main Methods:
- Analysis of 353,488 patient cases treated in California between 1984 and 1996.
- Utilized descriptive statistics and logistic regression to compare outcomes across three distinct time intervals: 1984-1987, 1988-1992, and 1993-1996.
- Examined in-hospital mortality and bypass surgery rates in relation to hospital PTCA procedure volume (<200 vs. >400 procedures/year).
Main Results:
- In-hospital mortality for low-volume (<200 PTCA/year) vs. high-volume (>400 PTCA/year) hospitals decreased from 2.5% vs. 1.3% (1984-1987) to 1.7% vs. 1.3% (1993-1996).
- Bypass surgery rates narrowed and decreased in low-volume vs. high-volume hospitals, from 12.4% vs. 6.9% to 4.6% vs. 3.3% over the study period.
- PTCA volume significantly predicted mortality and bypass rates, with outcome improvements in low-volume hospitals comparable to benefits seen in high-volume centers.
Conclusions:
- The disparity in outcomes between low- and high-volume hospitals for PTCA has significantly narrowed over time.
- All hospitals demonstrated substantial improvements in patient outcomes, irrespective of initial volume.
- Lower minimum volume standards for PTCA may be appropriate in underserved areas where angioplasty is otherwise unavailable.
Background:
Hospitals performing more surgical procedures tend to yield better outcomes. This study examines the evolution of this volume-outcome relation over time.
Methods And Results:
The relation between the number of percutaneous transluminal coronary angioplasty (PTCA) procedures performed at hospitals (volume) and in-hospital bypass surgery and death for 353 488 patients treated in California between 1984 and 1996 was examined. Descriptive statistics and logistic regression were used to compare outcomes for 3 periods: 1984 to 1987, 1988 to 1992, and 1993 to 1996. The in-hospital mortality rate was 2.5% for hospitals performing <200 PTCA procedures per year but only 1.3% for hospitals performing >400 procedures per year in 1984 to 1987. By 1993 to 1996, mortality rates in these 2 volume categories narrowed to 1.7% and 1.3%, respectively. Bypass surgery rates also narrowed and fell in low-volume (<200 procedures) versus high-volume (>400 procedures) hospitals from 12.4% versus 6.9% in 1984 to 1987 to 4.6% versus 3.3% in 1993 to 1996. In a logistic regression, PTCA procedures significantly predicted in-hospital mortality and bypass surgery rates in all 3 time periods. However, coefficient estimates indicate that improvements over time in outcomes for hospitals performing <200 procedures were comparable to the predicted benefits of increasing volume above 400 procedures within time periods.
Conclusions:
Over time, the disparity in outcomes between low- and high-volume hospitals has narrowed, and outcomes have improved significantly for all hospitals. Given these improvements, lower minimum volume standards may be advisable in less populated areas, where the alternative is no angioplasty at all.
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