Abstract 11686: The Myocardial Infarction and Cardiac Arrest Risk Calculator is an Accurate Discriminator of Major Adverse Events Following Elective Hip and Knee Surgery

Abstract

Background: The 2014 ACC/AHA guidelines on perioperative evaluation recommend differentiating patients at low-risk (<1%) versus elevated-risk (≥1%) for cardiac complications to guide appropriate preoperative testing. Among the tools recommended for estimating perioperative risk is the National Surgical Quality Improvement Program (NSQIP) Myocardial Infarction and Cardiac Arrest (MICA) risk calculator. The NSQIP MICA risk calculator showed good discriminating power when introduced in 2011, but has yet to be externally validated. The aim of the study was to investigate whether the NSQIP MICA risk calculator could accurately discriminate the incidence of major adverse events following elective hip and knee surgery. Methods: We reviewed 1,098 consecutive, elective orthopedic surgeries performed at Hershey Medical Center from January 2013 through December 2014, including 412 total hip replacements and 686 total knee replacements. Sufficient data were present to estimate risk using the NSQIP MICA risk calculator in 1,091 patients. Major adverse events were defined as myocardial infarction, cardiac arrest, or death within 30 days of surgery. A receiver operating characteristic curve was plotted from the estimated risk and adverse outcomes data. Results: Eight out of 1,091 procedures (0.7%) were complicated by a major adverse event. The mean estimated risk for adverse events using the NSQIP MICA risk calculator was 0.54% with a standard error of 0.018%. There was no significant difference (p=0.59) when comparing the observed versus expected incidence of major adverse events by chi-square test. The area under the curve (AUC) was determined to be 0.85 with a 95% confidence interval of 0.79-0.91 (see plot below). Conclusion: The NSQIP MICA risk calculator is a good discriminator of major adverse events following elective hip and knee surgery. Our study supports its use as a predictive tool for preoperative evaluation in this setting.