Substitution of fractionated for unfractionated heparin during high-risk percutaneous coronary intervention: has the problem been solved?

i t n ercutaneous coronary intervention (PCI) is frequently erformed in patients who received fibrinolytic therapy for cute myocardial infarction (MI). Currently, unfractionated eparin is the most commonly used antithrombin therapy in his situation. However, unfractionated heparin has certain imitations. It has a narrow therapeutic range, monitoring of he activated clotting time is required, and platelet activaion may be induced. For these reasons, considerable interst has been generated around the question of whether ow-molecular-weight heparin can be used in place of nfractionated heparin in the context of high-risk PCI. ow-molecular-weight heparin provides a more dependable nticoagulation response than unfractionated heparin, it has reater antifactor Xa:antifactor IIa activity, and it is less ikely to induce platelet activation (1). Importantly, howver, cases have been reported of catheterand guidewiressociated thrombosis during PCI procedures in conjuncion with the use of low-molecular-weight heparin (2,3). esults from the STEEPLE (Safety and Efficacy of Enoxparin in Percutaneous Coronary Intervention [PCI] Paients: an International Randomized Evaluation) trial sugest that, when used during elective PCI in low-risk atients, enoxaparin has similar or lower rates of bleeding ompared with unfractionated heparin (1). Unfortunately, he STEEPLE trial was not large enough to provide efinitive information about ischemic events and procedureelated thrombotic events. To date, we have only limited ata available regarding the safety and efficacy of lowolecular-weight heparin when used during PCI in highisk patients.