The Prequel

Troponins are recommended as the biomarkers of choice for the detection of myocardial infarction (MI) by the Universal Definition.1 This is well accepted for the diagnosis of type 1 or spontaneous MI, in which any elevation in the setting of ischemia is required but not for the diagnosis of type 4a or MI associated with percutaneous coronary intervention (PCI), in which an isolated 3× the upper reference limit elevation is required. Creatine kinase MB (CKMB) is widely favored because a number of studies support a relationship between CKMB elevation after PCI and long-term mortality with the cut-point appearing to be about 8 to 10× elevation of CKMB.2–5Article see p 150Troponins are much more sensitive than CKMB in detecting small areas of myocyte necrosis, but small amounts of myocyte necrosis may not be related to increased mortality6,7 In a meta-analysis of 4 studies with 2359 patients undergoing PCI, increases in troponin of >3 times upper reference limit were found in 14.5% and were associated at 18-month follow-up with increased events (death, MI, repeat target vessel PCI, and coronary artery bypass grafting) (odds ratio [OR], 2.25; 95% confidence interval [CI], 1.26–4.00).8 However, none of the studies used a 99th percentile cutoff with a sensitive troponin assay to define a normal baseline.The situation is complex because PCI may reduce the risk of death in high-risk patients, and the risk of a small amount of myocardial injury related to PCI may be balanced by the success of the PCI. On the other hand, PCI in a low-risk patient, if associated with myocardial injury, may be associated with an adverse prognosis. Furthermore, increased biomarker release may be a trade-off for optimal stent implantation and related to the amount of underlying atherosclerosis. The prognostic …