OBJECTIVES: We aimed to assess the differential implications of creatine kinase-myocardial band (CK-MB) and troponin measurement with the universal definition of periprocedural injury after percutaneous coronary intervention.BACKGROUND: Differentiation between definitions of periprocedural necrosis and periprocedural infarction has practical, sociological, and research implications. Troponin is the recommended biomarker, but there has been debate about the recommended diagnostic thresholds.METHODS: Thirty-two patients undergoing multivessel percutaneous coronary intervention and late gadolinium enhancement (LGE) cardiac magnetic resonance (CMR) imaging in a prospective study had cardiac troponin I, CK-MB, and inflammatory markers (C-reactive protein, serum amyloid A, myeloperoxidase, tumor necrosis factor alpha) measured at baseline, 1 h, 6 h, 12 h, and 24 h after the procedure. Three "periprocedural injury" groups were defined with the universal definition: G1: no injury (biomarker <99th percentile); G2: periprocedural necrosis (1 to 3 × 99th percentile); G3: myocardial infarction (MI) type 4a (>3 × 99th percentile). Differences in inflammatory profiles were analyzed.RESULTS: With CK-MB there were 17, 10, and 5 patients in groups 1, 2, and 3, respectively. Patients with CK-MB-defined MI type 4a closely approximated patients with new CMR-LGE injury. Groups defined with CK-MB showed progressively increasing percentage change in C-reactive protein and serum amyloid A, reflecting increasing inflammatory response (p < 0.05). Using cardiac troponin I resulted in 26 patients defined as MI type 4a, but only a small minority had evidence of abnormality on CMR-LGE, and only 3 patients were defined as necrosis. No differences in inflammatory response were evident when groups were defined with troponin.CONCLUSIONS: Measuring CK-MB is more clinically relevant for diagnosing MI type 4a, when applying the universal definition. Current troponin thresholds are oversensitive with the arbitrary limit of 3 × 99th percentile failing to discriminate between periprocedural necrosis and MI type 4a. (Myocardial Injury following Coronary Artery bypass Surgery versus Angioplasty: a randomised controlled trial using biochemical markers and cardiovascular magnetic resonance imaging; ISRCTN25699844).