Increased Regional Market Competition Lowers Threshold For Revascularization In Asymptomatic Carotid Artery Stenosis

Abstract

INTRODUCTION AND OBJECTIVES Revascularization practices for asymptomatic carotid stenosis(ACAS) vary widely among physicians. Our study examines the association of regional market competition with ACAS revascularization thresholds. METHODS We included all patients undergoing carotid revascularization in the VQI endarterectomy and stenting databases(2016-2020). High-grade stenosis was defined as ≥80%. We calculated the Herfindahl-Hirschman Index(HHI; measuring physician market competition) for US regions. Logistic regression was used to examine the association between degree of stenosis at revascularization with HHI stratified by symptomatology, adjusting for revascularization modality and traditional risk factors. RESULTS Of 92,243 carotid interventions, 61.9% were performed for ACAS and 38.1% for symptomatic carotid stenosis(SCAS). Patients undergoing revascularization for moderate-grade ACAS(vs. high-grade) were less likely to be on aspirin(85.6% vs. 86.3%) and clopidogrel(41.3% vs. 45.1%, both p<0.05), but equally likely to be on statins (85.6% vs. 85.7%, p=0.70). There were significant regional differences in the proportion of carotid revascularization procedures performed for moderate-grade ACAS(Figure). After adjusting for baseline differences between groups, market competition was independently associated with higher odds of revascularization for moderate versus high-grade ACAS(OR:1.02 per 10pt ΔHHI, 95%CI:1.01-1.03). There was no association of market competition with degree of carotid stenosis at time of revascularization among SCAS patients(OR:1.00 per 10pt ΔHHI, 95%CI:1.00-1.01). ACAS patients with moderate-grade stenosis had higher odds of in-hospital stroke or death compared to high-grade stenosis patients(OR:1.28, 95%CI:1.05-1.56). CONCLUSIONS Increased local market competition is associated with a lower revascularization threshold for ACAS but not SCAS. These findings, combined with the increased risk of perioperative stroke/death among moderate-grade ACAS patients, suggest that competition among physicians may result in a higher tolerance for increased operative risk in patients who might otherwise be reasonable candidates for surveillance. Revascularization practices for asymptomatic carotid stenosis(ACAS) vary widely among physicians. Our study examines the association of regional market competition with ACAS revascularization thresholds. We included all patients undergoing carotid revascularization in the VQI endarterectomy and stenting databases(2016-2020). High-grade stenosis was defined as ≥80%. We calculated the Herfindahl-Hirschman Index(HHI; measuring physician market competition) for US regions. Logistic regression was used to examine the association between degree of stenosis at revascularization with HHI stratified by symptomatology, adjusting for revascularization modality and traditional risk factors. Of 92,243 carotid interventions, 61.9% were performed for ACAS and 38.1% for symptomatic carotid stenosis(SCAS). Patients undergoing revascularization for moderate-grade ACAS(vs. high-grade) were less likely to be on aspirin(85.6% vs. 86.3%) and clopidogrel(41.3% vs. 45.1%, both p<0.05), but equally likely to be on statins (85.6% vs. 85.7%, p=0.70). There were significant regional differences in the proportion of carotid revascularization procedures performed for moderate-grade ACAS(Figure). After adjusting for baseline differences between groups, market competition was independently associated with higher odds of revascularization for moderate versus high-grade ACAS(OR:1.02 per 10pt ΔHHI, 95%CI:1.01-1.03). There was no association of market competition with degree of carotid stenosis at time of revascularization among SCAS patients(OR:1.00 per 10pt ΔHHI, 95%CI:1.00-1.01). ACAS patients with moderate-grade stenosis had higher odds of in-hospital stroke or death compared to high-grade stenosis patients(OR:1.28, 95%CI:1.05-1.56). Increased local market competition is associated with a lower revascularization threshold for ACAS but not SCAS. These findings, combined with the increased risk of perioperative stroke/death among moderate-grade ACAS patients, suggest that competition among physicians may result in a higher tolerance for increased operative risk in patients who might otherwise be reasonable candidates for surveillance.