Predictive value of perioperative
cardiac troponin I for adverse outcome in coronary artery bypass
surgery.
Eigel P, van Ingen G, Wagenpfeil S.
Department of Cardiac Surgery, Passau General Hospital, 94032,
Passau, Germany. eigel@fmi.uni-passau.de
OBJECTIVES: Cardiac Troponin I (cTnI) is a well-known marker
for myocardial damage in patients undergoing aorto-coronary bypass
grafting (CABG) peaking 6-8 h after aortic declamping. The aim
of this study was to evaluate cTnI release in the course of CABG
procedures early, i.e. after the cessation of cardiopulmonary
bypass (CPB) in order to recognize unstable cardiac function leading
to hemodynamic deterioration and resulting in an adverse outcome
(AO). AO is defined as the onset of myocardial infarction and/or
death peri/postoperatively. METHODS: Five-hundred and forty consecutive
patients who underwent CABG were evaluated for cTnI release immediately
prior to the induction of anesthesia (IND) and after termination
of CPB (END). Standard CPB with ante/retrograde cold blood cardioplegia
was used. Patients with any of the following criteria were excluded:
(1), CABG within 7 days of myocardial infarction; (2), emergency
operation for both unstable angina and for coronary occlusion
at angioplasty; (3), CABG with concomitant surgical cardiac procedures;
(4), preoperative renal dysfunction requiring hemodialysis; (5),
redos. Troponin I was measured with the Stratus CS fluorometric
enzyme immunoassay analyzer (Dade-Behring) running on site in
the operation room (OR), so values of cTnI could be obtained within
15 min. RESULTS: There were six deaths (1.1%) in the entire series,
Q-wave myocardial infarction occurred in 19 patients (3.5%), AO
was experienced by 21 patients (3.9%). The mean preoperative cTnI
level was 0.04+/-0.17 ng/l (mean+/-standard deviation) for the
entire group. The END cTnI level for the AO-group was 0.91+/-0.5
ng/l; for all other patients, this was 0.37+/-0.3 ng/l (P<0.001).
Changes in intraoperative cTnI levels relative to time course
showed a marked increase for the AO-group (0.0038+/-0.0035 ng/l*min)
as compared with non-AO patients (0.0019+/-0.0015 ng/l*min; P=0.028).
The receiver operating characteristic curve indicates a cTnI level
at CPB-end of higher than 0.495 ng/l with an area under the curve
of 0.83 as the optimal cut-off point for predicting AO with a
sensitivity and specificity of 76.2%. Stepwise logistic regression
analysis revealed END cTnI level (odds ratio, 17.24; P<0.001),
CPB time (odds ratio, 1.03; P=0.001), female sex (odds ratio,
3.8; P=0.011) as significant independent predictors for AO. Age
of over 70 years (P=0.8), Cleveland Clinic risk score (P=0.65),
diabetes (P=0.26), elevated preoperative creatinine level (P=0.77),
severe left ventricular dysfunction (P=0.51), the number of grafts
performed (P=0.15), and change of intraoperative cTnI level relative
to time course (P=0.94) did not reach statistical significance.
CONCLUSIONS: cTnI release as determined at the end of CABG procedures
represents a strong predictor of an AO after surgery. Analyzing
blood samples for cTnI with an automated device on site in the
OR provides for immediate results, so specific diagnostic and
therapeutic interventions can be performed before hemodynamics
deteriorate.
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