The management of patients with acute ST-elevation myocardial infarction (STEMI) relies on restoring blood flow to the occluded infarct artery. Prompt percutaneous coronary intervention (PCI) and stenting of the stenosis causing the occlusion reduces the risk of cardiac death and recurrent infarction.1 In about half of patients,2 stenoses are identified in non-infarct arteries at the time of the PCI, leading some operators to extend the procedure and carry out an immediate ‘preventive PCI’ in the non- infarct arteries, on the basis that this may prevent future serious cardiac events. Until recently, however, clinical guidelines recommended that PCI be limited to the infarct artery, because of concern that the benefit of preventive PCI may not outweigh the risks of the extended procedure.3,4