Troponin T, troponin I and creatine kinase-MB mass after elective coronary stenting.

OBJECTIVE

To assess whether and to what extent elective coronary stenting is associated with biochemical evidence of minor myocardial damage (MMD), as defined by the detection of abnormal post-procedural serum levels of one more among the following markers of ischaemic injury: creatine kinase (CK)-MB mass, troponin T (Tn-T) and troponin I (Tn-I).

METHODS

Nineteen elective procedure of coronary stenting were compared with a matched group of 25 conventional percutaneous transluminal coronary angioplasty (PTCA) procedures performed in our laboratory from March to June 1995. Cases with evolving or recent (< 2 weeks) myocardial infarction, chronic total occlusions and dilation of saphenous vein grafts were excluded. By definition, all of the patients had undergone uneventful deployment of a single palmaz-Schatz stent, with no chest pain and no persistent ECG changes after the procedure. Serum levels of CK-MB mass, Tn-T and Tn-I were determined at baseline and 6, 12 and 24 h after the procedure. The frequency of abnormal results was determined for each marker. Baseline and peak post-procedural levels in the two groups were compared and related to procedural variables.

RESULTS

Baseline values were normal in all cases. The quantitative analysis showed that post-procedural levels of each marker (including total CK) were significantly higher with respect to baseline in both groups. In the stent group, two patients had positive CK-MB mass, four positive Tn-T and seven positive Tn-I. Absolute changes in Tn-T and Tn-I were closely related to changes in CK-MB mass (r = 0.76, P < 0.0001; r = 0.90, P < 0.0001), respectively). Three of these patients developed clinically silent side-branch occlusion. All of them were positive for troponins and two were positive for CK-MB. No correlation was found between procedural variables and the results of biochemical assays. In the PTCA group, three patients were positive for Tn-I, whereas the CK-MB mass and Tn-T remained constantly normal. No side-branch occlusion was observed. The peak CK-MB mass and Tn-I were significantly higher in the stent group than they were in the PTCA group (3.04 +/- 4.1 versus 1.27 +/- 1.3 ng/ml, P = 0.046; 0.78 +/- 1.17 versus 0.28 +/- 0.3 ng/ml, P = 0.046, respectively). This difference was no longer apparent when patients with side-branch occlusion were excluded.

CONCLUSIONS

In our series, Tn-I measurement shows the highest ability to detect MMD, being positive in 37% of stent and 14% of PTCA cases. Elective coronary stenting associated with greater release of CK-MB mass and Tn-I than is conventional PTCA. This finding is mainly determined by cases of side branch occlusion, which account for most, but not all, periprocedural MMD in the stent group.