Background: Percutaneous coronary intervention (PCI) reduces mortality in most myocardial infarction (MI) patients but the effect on elderly patients with comorbidities is unclear. Our aim was to analyse the effect of PCI on in-hospital mortality of MI patients, by age, sex, ST elevation on presentation, diabetes mellitus (DM) and chronic kidney disease (CKD). Methods: Cohort study of 79,791 MI patients admitte...