Prognostic implication of cardiac troponin T increase following stent implantation. (Interventional Cardiology and Surgery).

Objective: To identify the incidence and clinical significance of myocardial injury following elective stent implantation.

Design: Prospective clinical study with 278 consecutive patients undergoing stenting of de novo coronary or saphenous vein graft lesions. Incidence of periprocedural myocardial injury was assessed by analysis of 12 lead ECG, creatine kinase (CK; upper limit of normal (ULN) 70 IU/I for women, 80 IU/I for men), and cardiac troponin T (cTnT; point of care test; threshold 0.1 ng/ml) before and 6, 12, and 24 hours after the intervention. Molar adverse cardiac events (MACE: acute myocardial infarction, bypass surgery, and cardiac death) were recorded during clinical follow up (mean (SD) 7.8 (5.3) months).

Results: Following elective stenting, the rate of a positive cTnT status was 17.3%, the rate of CK increase of 1-3x ULN 14.7%, the rate of CK increase of > 3x ULN 1.4%, and the rate of Q wave myocardial infarction 0.4%. Cardiac mortality during follow up was higher in patients with postprocedurally increased CK (7.1% v 1.3%, p = 0.01, log rank) and cTnT (9.1% v 0.9%, p < 0.001, log rank). In addition, postprocedurally increased cTnT was associated with a higher overall incidence of MACE (13.1% v 4.0%, p < 0.01, log rank) and was identified as an independent factor for MACE during follow up (hazard ratio 3.27, 95% confidence interval 1.14 to 9.41, p = 0.028).

Conclusions: Following elective stent implantation, a positive cTnT status identified patients at risk of a worse long term outcome. Treatment strategies hove to be developed that lead to prognostic improvement by reducing periprocedural myocardial injury.

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During the past two decades, coronary stenting either with predilatation (conventional stenting) or without predilatation (direct stenting) has become the leading type of percutaneous coronary intervention, and accounts for approximately 70% of all catheter based procedures. (1-4) Increasing experience, use of novel stent designs, and more effective antiplatelet treatment contributed to this development. (5 6) Yet the favourable impact on both short and long term clinical outcome remained the most important factor in the widespread use of stent implantation. (1-3)

Fundamental questions in clinical practice were, however, raised by various clinical trials, which showed a worse long term outcome for patients with increased creatine kinase (CK) following otherwise successful percutaneous coronary intervention. (7) By means of postprocedural analysis of cardiac troponin T (cTnT) or cardiac troponin I, even minor forms of these intervention related events have become detectable and were found to be higher with stent implantation than with balloon angioplasty. (8-9) Yet the prognostic significance of these minor forms of stenting related myocardial injury is still unknown.

Thus, the present study was designed to assess prospectively the incidence and prognostic significance of myocardial injury associated with direct and conventional stent implantation by serial analysis of cTnT, CK, and 12 lead EGG.

METHODS

Patient population

Between January 1998 and November 1999, all patients with successful single vessel stenting were included in this study unless they met at least one the following criteria: increased cardiac serum markers before intervention; acute myocardial infarction (AMI) during the two weeks before the procedure; terminal renal insufficiency, hypothyroidism, or skeletal muscle injury; vessel diameter < 2.5 mm; severe calcification or angulation of the target lesion; in-stent restenosis or chronic occlusion; and contraindication for aspirin, ticlopidine, or clopidogrel medication.

Procedural success was defined as a reduction in stenosis diameter < 30% without fatal complications or emergency coronary artery bypass grafting. The study was approved by the local council of human research and all patients gave written informed consent for the coronary procedure.

Interventional procedure

All interventional procedures were performed through the femoral route using tubular slotted stents only. It was left to the operator's discretion to choose between conventional stenting and direct stenting based on the vessel anatomy and personal preference. If angiography suggested incomplete stent expansion or residual stenosis > 30%, further high pressure balloon …