Perioperative urinary thromboxane metabolites and outcome of coronary artery bypass grafting: a nested case-control study.

Objective As a marker of in vivo thromboxane generation, high-level urinary thromboxane metabolites (TXA-M) increase the occurrence of cardiovascular events in high-risk patients. To investigate whether perioperative urinary TXA-M level is associated with major adverse cardiac and cerebrovascular events (MACCE) after coronary artery bypass graft (CABG) surgery, we designed a nested case-control study. Design Observational, nested case-control study. Setting Single-centre outcomes research in Fuwai Hospital, Beijing, China. Participants One thousand six hundred and seventy Chinese patients undergoing CABG surgery from September 2011 to October 2013. Methods We obtained urinary samples from 1670 Chinese patients undergoing CABG 1hour before surgery (pre-CABG), and 6hours (post-CABG 6hours) and 24hours after surgery (post-CABG 24hours). Patients were followed up for 1year, and we observed 56 patients had MACCE. For each patient with MACCE, we matched three control subjects. Perioperative urinary TXA-M of the three time spots was detected in these 224 patients. Results Post-CABG 24hours TXA-M is significantly higher than that of patients without MACCE (11101vs8849 pg/mg creatine, P=0.007). In addition, patients in the intermediate tertile and upper tertile of post-CABG 24hours urinary TXA-M have a 2.2 times higher (HR 2.22, 95%CI 1.04 to 4.71, P=0.038) and a 2.8 times higher (HR 2.81, 95%CI 1.35 to 5.85, P=0.006) risk of 1year MACCE than those in the lower tertile, respectively. Conclusions In conclusion, post-CABG 24hours urinary TXA-M elevation is associated with an increase of 1year adverse events after CABG, indicating that the induction of cyclo-oxygenase-2 by surgery-related inflammatory stimuli or platelet turnover may be responsible for the high levels of post-CABG urinary TXA-M. Trial registration number NCT01573143.