Abstract
BACKGROUND
Recent studies have suggested that immunoassay of cardiac troponin T (cTnT) provides a more sensitive measurement of myocardial necrosis than creatine kinase MB (CK-MB) mass concentration.
HYPOTHESIS
The purpose of this study was to compare the release of cTnT and CK-MB isoenzyme in patients undergoing percutaneous coronary angioplasty, and to investigate the clinical, procedural, and angiographic correlates of abnormal elevations of both of these markers.
METHODS
Total creatine kinase (total CK), CK-MB, and cTnT levels were measured immediately before and 12 h following intervention in 110 patients, including 100 consecutive patients undergoing coronary angioplasty and 10 control patients undergoing diagnostic cardiac catheterization. All patients had normal levels of all three markers at baseline. A postintervention total CK level > 225 U/l, an increase in CK-MB > 5.0 ng/ml, and/or an increase in cTnT > 0.04 ng/ml were considered indicative of myocardial injury.
RESULTS
Coronary angioplasty was successfully performed in all 100 patients without emergency bypass surgery or death, although six patients required emergent placement of an intracoronary stent for threatened closure. Eight patients demonstrated an abnormal increase in total CK, including six who were undergoing primary angioplasty for an acute myocardial infarction. One of these patients sustained a Q-wave infarction. Post angioplasty, 18 patients had elevations of both CK-MB and cTnT, 23 had elevations of only cTnT, and the remaining 59 patients had elevations of neither. All patients with CK-MB elevation also had cTnT elevation. Neither serologic marker increased in the diagnostic catheterization control patients. In comparison with patients without postintervention cTnT rise, patients with abnormal cTnT levels had a higher incidence of complex lesion morphology (p < 0.01) and intracoronary thrombus (p < or = 0.0001) prior to coronary angioplasty, and a higher incidence of coronary dissection (p < or = 0.01), abrupt closure (p < or = 0.05), and side-branch occlusion (p < or = 0.01) during angioplasty. In patients with elevation of both cTnT and CK-MB, postintervention CK-MB levels were 12-fold higher and cTnT levels were 21-fold higher than in patients with isolated elevation of only cTnT (p < 0.01).
CONCLUSIONS
These data indicate that > 40% of patients undergoing coronary angioplasty have evidence of minor degrees of myocardial damage, as evidenced by cTnT release. High-risk coronary lesions and both minor and major complications of angioplasty are associated with cTnT release. cTnT appears to be a more sensitive marker of myocardial injury than CK-MB under these circumstances. In comparison with isolated cTnT rise, elevation of both CK-MB and cTnT may be indicative of greater levels of myocardial injury.
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