Mortality impact of post-discharge myocardial infarction size after percutaneous coronary intervention: a patient-level pooled analysis from the 4 large-scale Japanese studies

It is unknown whether there is a threshold of creatine kinase (CK) or CK-MB affecting the subsequent mortality for post-discharge myocardial infarction (PDMI) after percutaneous coronary intervention. Current study sought to evaluate the impact of PDMI. The study population included 30,051 patients with successful coronary stenting and discharged alive in the pooled patient-level database of 4 Japanese studies (j-Cypher registry, CREDO-Kyoto PCI/CABG registry cohort-2, RESET, and NEXT). During 4.4 ± 1.4 year follow-up, 915 patients experienced PDMI (cumulative 5-year incidence of 3.6%). Among 466 patients with available peak CK ratio (peak CK/upper limit of normal), peak CK ratio (< 3) was present in 21% of patients, while peak CK ratios (≥ 3 and < 5), (≥ 5 and < 10), (≥ 10 and < 30), and (≥ 30) were present in 17, 25, 30, and 7.3% of patients, respectively. The excess mortality risk of patients with relative to those without PDMI for subsequent mortality was significant (adjusted HR 5.12, 95% CI 4.52–5.80, P < 0.001) by the Cox model with PDMI incorporated as the time-updated covariate. However, the mortality risk of patients in the smallest peak CK ratio category (< 3) was insignificant (HR 0.85, 95% CI 0.43–1.71, P = 0.65). In conclusion, despite significant overall mortality risk of PDMI, the mortality risk of small PDMI was similar to that of no PDMI, suggesting the presence of some threshold about infarct size influencing mortality.