Long-term outcomes of non-ST-elevation myocardial infarction without creatine kinase elevation: The J-MINUET study

Background: According to troponin-based criteria of myocardial infarction (MI), patients without elevation of creatine kinase (CK), formerly classified as unstable angina (UA), are now diagnosed as non-ST-elevation MI (NSTEMI), but little is known about their outcomes. Methods and Results: Between July 2012 and March 2014, 3,283 consecutive patients with MI were enrolled. Clinical follow-up data were obtained up to 3 years. The primary endpoint was a composite of all-cause death, non-fatal MI, non-fatal stroke, cardiac failure and urgent revascularization for UA. There were 2,262 patients with ST-elevation MI (STEMI), 563 NSTEMI with CK elevation (NSTEMI+CK) and 458 NSTEMI without CK elevation (NSTEMI-CK). From day 0, Kaplan-Meier curves for the primary endpoint began to diverge in favor of NSTEMI-CK for up to 30 days. The 30-day event rate was significantly lower in patients with NSTEMI-CK (3.3%) than in STEMI (8.6%, P<0.001) and NSTEMI+CK (9.9%, P<0.001). Later, the event curves diverged in favor of STEMI. The event rate from 31 days to 3 years was significantly lower in patients with STEMI (19.8%) than in NSTEMI+CK (33.6%, P<0.001) and NSTEMI-CK (34.2%, P<0.001). Kaplan-Meier curves from 31 days to 3 years were almost identical between NSTEMI+CK and NSTEMI-CK (P=0.91). Conclusions: Despite smaller infarct size and better short-term outcomes, long-term outcomes of NSTEMI-CK after convalescence were as poor as those for NSTEMI+CK and worse than for STEMI.