Minor cardiac troponin t release in patients undergoing coronary artery bypass graft surgery on a beating heart

Abstract

Objectives: To determine whether and to what extent coronary artery bypass graft (CABG) surgery without extracorporeal circulation is associated with cardiac troponin T (TnT) release. Design: Prospective study. Setting: A single university hospital. Participants: Twenty-three patients scheduled for minimally invasive CABG surgery. Sixteen patients received one coronary anastomosis, and seven received two. Interventions: TnT and creatine kinase-MB (CK-MB) levels were determined immediately before induction of anesthesia (baseline) and at 0, 12, and 24 hours after surgery. Hemodynamic measurements were made, and 5-lead electrocardiograms with continuous automated ST-segment trends were analyzed. Measurements and Main Results: All patients had a good cardiac outcome. Median cumulative coronary artery occlusion time was 27 minutes (range, 10 to 49 minutes). TnT levels were undetectable in 91.3% of patients at baseline when a detection limit of 0.01 ng/mL was employed. TnT and CK-MB showed significant elevations at 12 and 24 hours versus baseline. Postoperatively, TnT was detectable in 91.3% of patients, and 17.4% suffered minor myocardial damage, as evidenced by an abnormal increase in TnT greater than 0.2 ng/mL, excluding those exhibiting myocardial infarction. ST segment changes developed in seven patients, persisting for 13.0 minutes (range, 9.5 to 15.8 minutes) and disappearing immediately after coronary artery clamp release. There were no significant correlations between cumulative coronary occlusion time and peak TnT or CK-MB levels. Conclusions: TnT was detected after surgery in most patients, and significant TnT levels indicative of myocardial injury (>0.2 ng/mL) were detected in only 17% of patients, probably as a result of brief periods of coronary artery occlusion.