Assessing MICRO-vascular resistances via IMR to predict outcome in STEMI patients with multivessel disease undergoing primary PCI (AMICRO): Rationale and design of a prospective multicenter clinical trial

Background In STEMI patients treated with primary percutaneous coronary angioplasty (PPCI) the evaluation of coronary microcirculatory resistance index (IMR) predict the extent of microvascular damage and left ventricular (LV) remodeling. However, the impact of IMR on the clinical outcome after PPCI in patients with multivessel disease (MVD) remains unsettled. Aim We designed a prospective multicenter controlled clinical trial to evaluate the prognostic value of IMR in terms of clinical outcome and left ventricular remodeling in STEMI patients with MVD undergoing PPCI. Methods and design The study will involve 242 patients with MVD defines as the presence of at least a non-culprit lesion of >50% stenosis at index coronary angiography. Both fractional flow reserve (FFR) and IMR will be measured in the infarct-related artery (IRA) after successful PPCI. Measurements of FFR and IMR will be repeated in the IRA and performed in the non-culprit vessels at staged angiography. The non-culprit vessel lesions will be treated only in the presence of a FFR Implications If IMR significantly correlates with differences in outcome and LV remodeling, it will emerge as a potential prognostic index after PPCI in patients with MVD.