TCT-345 Optical coherence tomography appraisal of residual thrombus burden in patients with ST-segment elevation myocardial infarction undergoing bivalirudin versus unfractionated heparin infusion. The MATRIX (Minimizing Adverse Haemorrhagic Events by TRansradial Access Site and angioX) OCT study

BACKGROUND Residual stent strut thrombosis, which is a consistent finding after primary PCI, negatively affects myocardial perfusion and may increase stent thrombosis risk. Objectives: to assess whether a strategy of either prolonged bivalirudin (PB) or intra-procedural-only (IB) administration infusion reduces residual stent strut thrombosis as compared to unfractionated heparin in subjects with ST elevation myocardial infarction (STEMI). METHODS Multivessel STEMI patients undergoing primary PCI and requiring staged intervention were selected among those allocated to either PB or IB in the MATRIX (Minimizing Adverse Haemor- rhagic Events by TRansradial Access Site and angioX) Treatment- Duration study. Those receiving heparin only were enrolled into a registry arm. Optical coherence tomography (OCT) of the infarct- related artery was performed at the end of primary PCI and four to five days thereafter during staged intervention. The primary endpoint was the change in minimum flow area (DMinFA) defined as: [stent area þ incomplete stent apposition (ISA) area] - (intra- luminal defect þ tissue prolapsed area) between index and staged PCI. RESULTS Between September 2013 and November 2015, 316 patients were screened and 137 were randomized to either IB (N1⁄464) or PB (N1⁄473) and 28 patients were enrolled in the unfractionated heparin arm. Mean stent area, percentage of malapposed struts and mean percent thrombotic area were comparable after index or staged PCI. DMinFA [IB: 0.22 (-0.04 - 0.68), PB: 0.32 (-0.01 - 0.86) and Heparin 0.05 (-0.61, 0.43) mm2; P1⁄40.049 for the comparison IB vs Heparin and P1⁄40.024 for the comparison PB vs Heparin]. CONCLUSION Either prolonged or intra-procedural-only administra- tion of bivalirudin after primary PCI did reduce residual stent strut thrombosis as compared to unfractionated heparin. This observation should be considered hypothesis generating since the heparin treat- ment to patients was not randomly allocated.