Mildly Elevated Cardiac Troponin below the 99th-Percentile Upper Reference Limit after Noncardiac Surgery

BACKGROUND AND OBJECTIVES: In patients with perioperative cardiac troponin (cTn) I below the 99th-percentile upper range of limit (URL), mortality according to cTn I level has not been fully evaluated. This study evaluated the association between postoperative cTn I level above the lowest limit of detection but within the 99th-percentile URL and 30-day mortality after noncardiac surgery. METHODS: Patients with cTn I values below the 99th-percentile URL during the perioperative period were divided into a no-elevation group with cTn I at the lowest limit of detection (6 ng/L) and a minor elevation group with cTn I elevation below the 99th percentile URL (6 ng/L < cTn I < 40 ng/L). The primary outcome was 30-day mortality. RESULTS: Of the 5,312 study participants, 2,582 (48.6%) were included in the no-elevation group and 2,730 (51.4%) were included in the minor elevation group. After propensity score-matching, the minor elevation group showed significantly increased 30-day mortality (0.5% vs. 2.3%; hazard ratio, 4.30; 95% confidence interval, 2.23–8.29; p<0.001). The estimated cutoff value of cTn I to predict 30-day mortality was 6 ng/L with the area under the receiver operating characteristic curve 0.657. CONCLUSIONS: A mild elevation of cTn I within the 99th-percentile URL after noncardiac surgery was significantly associated with increased 30-day mortality as compared with the lowest limit of detection. TRIAL REGISTRATION: Clinical Research Information Service Identifier: KCT0004244