Some research has demonstrated that performing elective percutaneous coronary interventions (PCI) in low-volume facilities, especially those without onsite cardiac surgery, can result in positive outcomes. Critics say, however, that these studies are mostly single-center investigations, which do not reflect the real risk of performing elective PCI without onsite surgical backup. In fact, critics point to studies using Medicare data, which do show an increase in mortality for patients treated at facilities without surgical backup.