A New Index for Pre-Operative Cardiovascular Evaluation

Abstract

Background: Currently used indices for pre-operative cardiovascular evaluation are either powerful, but complex, or simple, but with weak discriminatory power.

Objectives: This study sought to prospectively derive and validate a simple powerful index that can stratify the cardiovascular risk of patients undergoing noncardiac surgery.

Methods: The derivation cohort consisted of 3,284 prospectively enrolled adult patients undergoing noncardiac surgery at the American University of Beirut Medical Center. The validation cohort consisted of 1,167,414 patients registered in the American College of Surgeons National Surgical Quality Improvement Program database. The primary outcome measure was death, myocardial infarction, or stroke at 30 days after surgery.

Results: The primary outcome occurred in 38 patients (1.2%) in the derivation cohort. Multivariate logistic regression analysis in the derivation cohort identified 6 data elements to be included in the prediction model: age ≥75 years, history of heart disease, symptoms of angina or dyspnea, hemoglobin <12 mg/dl, vascular surgery, and emergency surgery. Each patient was assigned a Cardiovascular Risk Index (CVRI) of 0, 1, 2, 3, and >3 based on the number of data elements present. The incidence of the primary outcome increased steadily across the CVRI groups in both the derivation (0%, 0.5%, 2.0%, 5.6%, and 15.7%, respectively; p < 0.0001) and validation (0.3%, 1.6%, 5.6%, 11.0%, and 17.5%, respectively; p < 0.0001) cohorts. The discriminatory power of the new CVRI was further confirmed by constructing a receiver-operating characteristic curve that had an area under the curve of 0.90 in the derivation cohort and 0.82 in the validation dataset.

Conclusions: This study reports a new index for pre-operative cardiovascular evaluation which has a strong discriminatory power that can effectively stratify patients into low- (CVRI 0 to 1), intermediate- (CVRI 2 to 3), and high-risk (CVRI >3) groups. This has important implications for the efficient triage and management of patients scheduled for noncardiac surgery.

Keywords: cardiovascular risk index; noncardiac surgery; pre-operative cardiovascular evaluation.