Myocardial Perfusion Imaging Failed to Improve Patient Risk Classification Compared to the Revised Cardiac Risk Index for Early Cardiac Complications After Major Non-Cardiac Surgery

Abstract

Cardiac evaluation is desirable before major non-cardiac surgery with myocardial perfusion imaging (MPI) frequently utilised for risk assessment. However, the prognostic utility of MPI above a simple clinical risk calculator, the Revised Cardiac Risk Index (RCRI), is unknown. We conducted a retrospective cohort study of patients who underwent MPI before major non-cardiac surgery, incorporating 635 surgical procedures in 629 patients over six years. Major adverse cardiac events (MACE) within 30 days of surgery, including any myocardial infarction, acute pulmonary oedema, ventricular arrhythmia, or cardiac death, occurred in 47 (7.4%) cases. We analysed predictive value of MPI for MACE using multivariable logistic regression and categorical net reclassification index. MPI-identified medium or large-sized reversible perfusion defects (p=0.02, odds ratio 2.9 [95% CI 1.1-7.1]) and RCRI score two or more (p=0.03, odds ratio 2.3 [(95% CI 1.1-4.8]) were significantly associated with MACE after adjusting for age, coronary revascularisation, surgical acuity, need for general anaesthesia, left ventricular ejection fraction (LVEF) and fixed perfusion defects. Net reclassification index comparing models with and without MPI risk factors (LVEF, reversible perfusion and fixed perfusion defects) did not significantly improve risk classification. MPI risk factors are weak predictors for early cardiac complications after major non-cardiac surgery and failed to improve patient risk classification beyond a simple risk assessment using age, RCRI and surgical priority. Clinicians should consider alternative risk assessment strategies because of MPI's poor prognostic utility and its associated time and financial costs.