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<0.75. A 2D echocardiographic evaluation of the left ventricular (LV) volumes and ejection fraction will be performed before hospital discharge and at 1-year follow-up. The primary end-point of the study will be the composite of cardiovascular death, re-hospitalization for heart failure and resuscitation or appropriate ICD shock during 1-year of follow-up. Secondary end-points will be the impact of IMR in predicting LV remodeling during follow-up and correlations between IMR and ST-segment resolution. Other secondary endpoints will be need for new revascularization, stent thrombosis and re-infarction of the non-culprit vessels territory. 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.