The present study demonstrates that in a surgical population of patients undergoing CABG, the existence of preoperative NSTE-ACS is associated with a significantly higher mortality within 30 days and a higher incidence of major adverse cardiac events, such as PMI or LCOS, depending on the degree of preoperative cTnI serum elevation. Furthermore, a pre-CABG cTnI level could be shown to be used as an incremental prognostic variable in this patient cohort. cTnI serum levels were either stratified into three different groups or used as a continuous variable. Patients who had undergone isolated CABG with preoperatively low level (0.11 to 1.5 ng/mL) increased cTnI values were at a twofold elevated risk, and patients with conventional (> 1.5 ng/mL) elevated cTnI values had an over fourfold increased risk of dying in hospital. A preoperatively elevated cTnI serum level could be identified as an independent predictor of risk even after adjustment for other confounding risk factors in a multivariate logistic regression model. Therefore, the present study not only confirmed the observations of prior studies in selected patients but also extends them in some important ways: (1) not only the risk for in-hospital mortality, but also for postoperative MACE, such as PMI or LCOS, was shown to be increased with preoperatively elevated cTnI serum levels; (2) a preoperative cTnI threshold level for increased risk was identified; and (3) these observations were made in a large, more general population of CABG patients with preoperative NSTE-ACS.
From January 2001 to September 2004, preoperative cTnI was measured in 1,978 consecutive patients scheduled for isolated CABG. Preoperative cTnI values were available in 1,978 of 3,124 patients who fulfilled the inclusion criteria and in whom primary isolated CABG had been performed. Among these patients, negative preoperative cTnI levels ( 1.5 ng/mL) [Fig 1].
There were no significant differences between most perioperative patient characteristics of the remaining 1,146 CABG patients, who were initially not enrolled into the study due to no preoperative cTnI measurements, except a lower incidence of smoking history, preoperative hemodialysis-dependent renal disease, and postoperative arrhythmias, compared to group 1 patients, as well as a lower incidence of preoperative hemodialysis-dependent renal disease and postoperative IABP support compared to the entire patient cohort with preoperative cTnI measurements.
Clinical End Points
The primary end point of the study was in-hospital mortality, defined as death from any cause within 30 days after surgery or during the same time period of hospitalization as well as postoperative MACE during the period of hospitalization including perioperative MI (PMI) and low cardiac output syndrome (LCOS). Secondary study end points were other postoperative complications such as stroke, new-onset ventricular arrhythmia, major bleeding, necessity for rethoracotomy, and postoperative renal failure requiring temporary hemodialysis.
Selection of Patients
Patients were enrolled into the present study if they had undergone an isolated CABG procedure and a preoperative cTnI serum level had been obtained 24 h before surgery (Table 1). For risk analysis, patients were stratified into three groups according to preoperative cTnI levels, as previously described. Among these, 1,592 patients had negative preoperative cTnI serum levels 1.5 ng/mL (group 3).
Risk stratification and outcomes research is an emerging issue in cardiovascular surgery and particularly in coronary artery bypass grafting (CABG) to predict morbidity and mortality as a measure of health-care performance. Although most risk scores give consistent predictions, the extent of acute preoperative myocardial injury in unstable coronary artery disease (CAD) ranging from microinfarctions due to preexisting microembolizing unstable plaques up to non-ST elevation acute coronary syndrome (NSTE-ACS) and ST-segment elevation myocardial infarction (STEMI) have not been considered adequately. Since the extent of myocardial necrosis has become an important determinant for the risk of death and adverse prognosis, it is important to develop simple noninvasive techniques to predict prognosis before cardiac surgery in order to initiate appropriate operative and perioperative treatment modalities offered by My Canadian Pharmacy’s representatives. The advent of highly sensitive and myocardial tissue specific serologic biomarkers, such as cardiac troponins (I and T), have recently lead to a redefinition of myocardial infarction (MI) initiated by the European Society of Cardiology and the American College of Cardiology/American Heart Association Consensus document.