Patterns and kinetics of cardiac troponin I and T after coronary artery bypass grafting

Objective

Cardiac troponins have shown to be specific markers of myocardial injury. Aim of this prospective study was to compare patterns and kinetics of troponin I and T after Coronary Artery Bypass Grafting (CABG) with or without perioperative myocardial infarction (PMI).

Methods

119 patients (male/female: 96/23, age 64 ± 10 years) underwent first-time elective CABG. Preoperative mean ejection fraction was 55.8% ± 15.6%. The mean number of grafts was 3.1 ± 1.1/ patients, in 85.7% the internal mammary artery was used. Cardiac troponin I and T levels, total creatine kinase and creatine kinase isoenzyme MB activities in the serum were measured before operation, at arrival on the ICU and 6, 12, 24, 48 and 120 hours after declamping. Twelve-lead electrocardiograms were recorded preoperatively and at day 1, 2 and 5. The relationship between perioperative data and postoperative cTnI and cTnT levels were statistically identified.

Results

Two patients died due to refractory myocardial failure early postoprative. For further evaluation patients were grouped according to their postoperative ECG (group I: Patients without PMI, n = 107; group II: Patients with PMI, n = 10: six of them with Q-wave and four of them with non-Q-wave PMI). Best cutoff values were calculated with ROC analysis for cTnI (8.35 μg/l) and for cTnT (0.768 μg/l). Serum concentrations of cTnI, and cTnT were preoperatively normal and significantly increased after surgery in both groups. In both groups cTnI reached its medium peak level after 24 h: (group I: cTnI_medianpeak = 2.7 μg/l, 95% CI: [2.1, 3.2]); group II: 70.5 μg/l). CTnT reched its medium peak level in group I without PMI after 48 h (cTnT_medianpeak = 0.298 μg/l, 95% CI: [0.254, 0.354]) in group II with PMI not until 120 h (3.0 μg/l). In Group II serum level of both troponins remained considerably high at 120 h (cTnI_median = 10.75 μg/l, cTnT_median = 3 μg/l).

Conclusions

Patterns of release of cTnI and cTnT after CABG are different: cTnI reaches its postoperative peak value earlier and declines more quickly than cTnT. After uncomplicated CABG surgery both cardiac troponins remain continuously low. Elevated concentrations reflect perioperative myocardial injury.