Study Evaluates Impact of Competition on Hospitals' Early Adoption of EVAR

September 3, 2013—The Society for Vascular Surgery (SVS) announced the publication of a study that examined the hypothesis that hospitals in competitive markets adopted endovascular aneurysm repair (EVAR) earlier and had improved outcomes in treating abdominal aortic aneurysms (AAAs) than those in less-competitive markets. Rosh K.V. Sethi, BS, et al published the study in the SVS's Journal of Vascular Surgery (2013;58:596–606). The study was led by Louis L. Nguyen, MD, of Brigham and Women's Hospital and Harvard Medical School in Boston, Massachusetts.

The SVS noted that the share of total AAA repairs in the United States performed via EVAR increased from 32% in 2001 to 65% in 2006, with considerable variation between the states.

In the study, the investigators queried the Nationwide Inpatient Sample and linked Hospital Market Structure (HMS) data for patients who underwent EVAR for nonruptured AAAs in 2003. They also queried the same cohort of patients for post-AAA repair outcomes, including in-hospital death, length of stay, and vascular complications (eg, graft complications, embolism, or infection), and major postoperative complications as defined by the National Surgical Quality Improvement Program.

As summarized by the SVS, a weighted total of 21,600 patients was included in the analyses. Of these patients, 48.52% underwent EVAR. Patients at more competitive hospitals—lower Herfindahl Hirschman Index (HHI)—were at increased odds of undergoing EVAR versus open repair (odds ratio, 1.127 per 0.1 decrease in HHI; P < .0127) after adjusting for patient demographics, comorbidities, and hospital-level factors (bed size, teaching status, AAA repair volume, and ownership). Competition was not associated with differences in in-hospital mortality or vascular, neurologic, or other minor postoperative complications.

Bivariate and multivariable linear and logistic regression analyses for the dependent variable of EVAR use, including state level variables (number of malpractice claims, average malpractice claim payment, average number of vascular surgeons, and average health expenditures per state) were included to control for potential confounders in previous studies. A propensity score-adjusted, multivariable, logistic regression model was used as a control for treatment bias in assessing the effect of competition in AAA repair outcomes. The hope is that these results may help to guide future health care policy and limit the growing costs associated with vascular technology development, noted the investigators.

​“In the HMS, the HHI (range, 0–1) is a validated and a widely accepted economic measure of competition,” commented Dr. Nguyen in the SVS announcement. “Hospital markets were defined using a variable geographic radius that encompassed 90% of discharged patients. Market definition accounts for the fact that hospitals do not compete within confined geographic boundaries.”  
Dr. Nguyen continued, “We found that greater hospital competition in 2003 was significantly associated with increased EVAR adoption at a time when diffusion of this technology passed its tipping point. However, hospital competition does not influence post-AAA repair outcomes, but might improve outcomes like in-hospital mortality and length of stay.” 

“Our findings suggest that adoption of novel vascular technology is not solely driven by clinical indications, but may be influenced by market forces. For example, hospitals in competitive markets may be more likely to distinguish themselves from the competition by offering new procedures or services, especially when there are distinct differences included in procedures such as EVAR. The hospitals also may have a higher volume, greater expertise, and greater resources to become early adopters,” concluded Dr. Nguyen, who also noted that the general perception is that with more competition, costs will be lowered for a product or service, but evidence suggests that competition may not affect cost and might even increase it.