Cardiac troponin I and T in patients with impaired renal function after heart surgery

Objective

Cardiac troponins are specific markers of myocardial injury but the effects of renal dysfunction on postoperative levels remain unclear. In a prospective study postoperative troponin concentrations were evaluated in patients with normal or high serum-creatinine.

Methods

One hundred and ninety-one patients after elective heart surgery without myocardial infraction were divided into two groups according to serum creatinine. Group I included patients with serum creatinine < 1.3 mg/dl (n = 106), group II patients with serum creatinine ≥ 1.3 mg/dl (n = 85). CTnI and cTnT serum levels were measured before, and 6, 12, 24, 48 and 120 hours after the operation. Serum creatinine and urea concentrations as well as 12-lead electrocardiograms were recorded preoperatively, on the ICU and on day 1, 2 and 5. Levels and variability of troponin concentrations were expressed by median, first and third quartiles and analyzed by non-parametric methods.

Results

Pre-operative concentrations of both troponins were normal, but increased after surgery in all patients. Maximal slope of cTnI in group I ranged between 1.2 and 4.9 μg/l (X_med = 2.1 μg/l) and in group II between 2.1 and 5.9 μg/l (X_med = 2.9 μg/l). Maximal slope of cTnT ranged between 0.145 (I) and 0.474 μg/l (X_med = 0.274 μg/l) and 0.212 and 0.650 μg/l (X_med = 0.406 μg/l) (II). Serum concentrations of cTnI and cTnT in group II were significantly higher (P = 0.003 [cTnI], P = 0.002 [cTnT]).

Conclusions

In all patients cardiac troponin concentrations postoperatively increased, but patients with pre-operatively normal creatinine presented lower serum concentrations of both troponins than those with high creatinine values. These results indicate that for postoperative interpretation of troponins the status of renal function must be taken into account.