Comparison of cardiac troponin T and I and CK-MB for the detection of minor myocardial damage during interventional cardiac procedures

A number of cardiac interventional procedures are available for the treatment of angina, including percutaneous transluminal coronary angioplasty (PTCA), stent insertion and rotational atherectomy (RA). Variable degrees of myocardial cell injury during PTCA and stent insertion have been observed, based on rises in creatine kinase MB isoenzyme (CK-MB) and cardiac troponin T (cTnT) 6 24h post-procedure. As there are many variations in technique within each procedure it would be helpful to be able to determine objectively the degree of myocardial damage in order to optimize technique. We measured CK-MB, cTnT and cardiac troponin I (cTnI) to ascertain which is the most sensitive marker for minor myocardial damage in this setting. Blood samples were taken both before and 6, 14 and 24h after the procedure in 109 patients (77 men) with angina, 42 of whom had unstable angina. Of the 109 patients, 86 had a stent inserted (21 as a primary stent), nine had PTCA, eight had RA and six intracoronary brachytherapy. Using the manufacturers' recommended cut-offs - CK-MB 4 mug/L, cTnI and cTnT 0.1 mug/L - five patients were excluded from further analysis as all three markers were raised pre-procedure. Post procedure all three markers were in agreement for 68 patients (44 all normal, 24 all raised). Overall, CK-MB was raised in 28 patients, cTnT in 38 and cTnI in 58. In 19 patients CK-MB and cTnT were normal, but cTnI was raised (15 between 0.11 and 0.30 mug/L). cTnI was the most sensitive indicator of minor myocardial damage, but at the recommended cut-off of 0.1 mug/L may be overly sensitive. We await the results of our follow-up study to determine the clinical implications of these small rises in cTnI.