Optical coherence tomography appraisal of residual thrombus burden in patients with ST-segment elevation myocardial infarction undergoing intraprocedural versus post-stenting prolonged bivalirudin infusion. Rationale and design of the MATRIX (Minimizing Adverse Haemorrhagic Events by TRansradial Access Site and angioX) OCT substudy.

Aims: Residual thrombus accumulation around stent struts has been observed after the end of primary PCI and may represent a risk factor for acute stent thrombosis. The aim of this study is to test whether a strategy of prolonged bivalirudin infusion may reduce thrombosis of stent struts as compared to an intraprocedural only administration in subjects undergoing primary PCI. Methods and results: One hundred and sixty patients will be selected from the MATRIX (Minimizing Adverse Haemorrhagic Events by TRansradial Access Site and angioX) study with all the following inclusion criteria: a) STEMI patients undergoing primary PCI with stent implantation, b) randomisation to standard or prolonged bivalirudin treatment arm, and c) at least one critical (>70%) stenosis of non-infarct-related coronary vessels suitable for staged PCI. Optical coherence tomography (OCT) of the infarct-related artery will be performed at the end of primary PCI and at the time of staged PCI which will be performed three to five days after the index procedure. The percentage difference in minimal flow area and in the number of stent cross-sections with a thrombotic area >5% will be measured at the end of primary PCI and at the time of staged PCI. Conclusions: The MATRIX OCT substudy will establish whether prolonging the infusion of bivalirudin after the end of primary PCI may reduce the amount of residual thrombotic material on stent struts. The effect of the long-infusion strategy on clinical outcome will be elucidated by the MATRIX study.