Regional Variation in Postoperative Myocardial Infarction in Patients Undergoing Vascular Surgery in the United States

Abstract

Background: The aim of this study is to assess for regional variation in the incidence of postoperative myocardial infarction (POMI) following nonemergent vascular surgery across the United States to identify potential areas for quality improvement initiatives.

Methods: We evaluated POMI rates across 17 regional Vascular Quality Initiative (VQI) groups that comprised 243 centers with 1,343 surgeons who performed 75,057 vascular operations from 2010 to 2014. Four procedures were included in the analysis: carotid endarterectomy (CEA, n = 39,118), endovascular abdominal aortic aneurysm (AAA) repair (EVAR, n = 15,106), infrainguinal bypass (INFRA, n = 17,176), and open infrarenal AAA repair (OAAA, n = 3,657). POMI was categorized by the method of diagnosis as troponin-only or clinical/ECG and rates were investigated in regions with ≥100 consecutive cases. Regions with significantly different POMI rates were defined as those >1.5 interquartile lengths beyond the 75th percentile of the distribution. Risk-adjusted rates of POMI were assessed using the VQI Cardiac Risk Index all-procedures prediction model to compare the observed versus expected rates for each region.

Results: Overall rates of POMI varied by procedure type: CEA 0.8%, EVAR 1.1%, INFRA 2.7%, and OAAA 4.2% (P < 0.001). Significant variation in POMI rates was observed between regions, resulting in differing ranges of POMI rates for each procedure: CEA 0.5-2.0% (P = 0.001), EVAR 0.3-3.1% (P < 0.001), INFRA 1.1-4.8% (P < 0.001), and OAAA 2.2-10.0% (P < 0.001). A single region in 3 of the 4 procedure-specific datasets was identified as a statistical outlier with a significantly higher POMI rate after CEA, EVAR, and OAAA; this region was identical for the EVAR and OAAA datasets but was a different region for the CEA dataset. No significant variation in POMI was noted between regions after INFRA. Procedure-specific clinical POMI rates (mean; range) were significantly different between regions for EVAR (0.4%; 0-1.1%, P = 0.01) and INFRA (1.4%; 0.5-2.9%, P = 0.01), but not for CEA (0.4%; 0-0.8%, P = 0.53) or OAAA (1.6%; 0-3.8%, P = 0.23). Procedure-specific troponin-only POMI rates (mean; range) were significantly different between regions for all procedures: CEA (0.4%; 0.1-1.2%, P < 0.001), EVAR (0.7%; 0-2.1%, P < 0.001), INFRA (1.3%; 0.4-2.5%, P = 0.001), and OAAA (2.5%; 0-8.5%, P < 0.001). After risk adjustment, regional variation was again noted with 3 regions having higher and 4 regions having lower than expected rates of POMI.

Conclusions: Significant variation in POMI rates following major vascular surgery exists across VQI regions even after risk adjustment. These findings may present an opportunity for focused regional quality improvement efforts.