This study compared prognoses of myocardial infarction related to percutaneous coronary intervention (PCI, procedural MI) using increasing creatine kinase-myocardial band (CK-MB) thresholds with spontaneous MI.
Procedural MI usually is defined by a CK-MB elevation of more than 3 times the upper limit of normal (ULN), but higher thresholds have been proposed.
Patients from the EARLY-ACS (Early Glycoprotein IIb/IIIa Inhibition in Non–ST-Segment Elevation Acute Coronary Syndrome) study and the SYNERGY (Superior Yield of the New strategy of Enoxaparin, Revascularization and GlYcoprotein IIb/IIIa inhibitors) study treated with PCI were included. The primary end point was 1-year all-cause mortality from 24 h after PCI. To determine an enzymatic threshold for procedural MI with a prognosis similar to that of spontaneous MI, we redefined procedural MI using increasing CK-MB thresholds and compared corresponding hazard ratios with those of spontaneous MI (CK-MB more than twice the ULN). Hazard ratios for mortality for procedural and spontaneous MI were calculated using Cox proportional hazards regression and Global Registry of Acute Cardiac Events covariates for risk adjustment.
Nine thousand eighty-seven patients who underwent PCI (46.8%) were included; 773 procedural MI and 239 spontaneous MI occurred within 30 days. Adjusted hazard ratios for 1-year death were 1.39 (95% confidence interval [CI]: 1.01 to 1.89) for procedural MI and 5.37 (95% CI: 3.90 to 7.38) for spontaneous MI. The CK-MB threshold for procedural MI that achieved the same prognosis as spontaneous MI was 27.7 times the ULN (95% CI: 13.9 to 58.4), but this differed between the SYNERGY study (57.9 times the ULN, 95% CI: 17.9 to 63.6) and the EARLY-ACS study (20.4 times the ULN, 95% CI: 5.16 to 24.2). Of all procedural MI, 49 (6%) had CK-MB elevations of 27.7 or more times the ULN.
The current enzymatic definition of procedural MI (CK-MB more than 3 times the ULN) used in clinical trials is less strongly associated with death than that of spontaneous MI. Procedural MI achieves similar prognosis for 1-year mortality when much higher CK-MB thresholds are applied.