Predicting mortality in cardiac care unit patients: external validation of the Mayo cardiac intensive care unit admission risk score.

Abstract

The Mayo Cardiac Intensive Care Unit Admission Risk Score (M-CARS) had excellent performance in predicting in-hospital mortality in the US population. We sought to validate the M-CARS for in-hospital and post-discharge mortality in Asian patients admitted to the cardiac care unit (CCU). Patients admitted to the CCU of a tertiary care centre between July 2015 and December 2019 were included into the study. Patients with intra-hospital transfer to the CCU due to intensive care unit overflow, postoperative cardiac surgery, or for monitoring after elective procedures were excluded. Cardiac arrest, cardiogenic shock, respiratory failure, Braden skin score, blood urea nitrogen, anion gap, and red cell distribution width, were used to calculate the M-CARS. Patients were stratified into three groups, according to the M-CARS (<2, 2-6, >6). Of 1988 patients in the study, 30.1% were female with a median age of 65 years. Prevalence of cardiogenic shock and respiratory failure at admission were 2.8% and 4.5%, respectively. One hundred and seventeen patients died during the admission (mortality rate of 5.9%). The in-hospital mortality rate in patients with M-CARS of <2, 2-6, and >6 was 1.1%, 9.8%, and 35.5%, respectively. C-statistic of M-CARS for in-hospital mortality was 0.840 (95% CI 0.805-0.873); whereas, it was 0.727 (95% CI 0.690-0.761) for 1-year post-discharge mortality. Calibration plot showed good agreement between predicted and observed in-hospital mortality in the majority of patients. The M-CARS was useful in our study, in terms of discrimination and calibration. M-CARS identified high-risk patients in CCU, who had unacceptably high mortality rate during hospital stay and thereafter.