Resistance to flow in the coronary microcirculation – we can measure it but what does it mean?

In this edition of EuroIntervention there are two papers addressing different aspects of the use of the index of microcirculatory resistance (IMR) in patients with stable ischaemic heart disease (SIHD) and acute ST-elevation myocardial infarction (STEMI).

The group from Oxford in the UK in collaboration with colleagues from Rome, Italy, has previously reported that a novel score called ATI predicted elevated IMR (>40) after stenting in patients undergoing primary percutaneous coronary intervention for STEMI1. The score incorporates age (>50 years), angiographically assessed thrombus burden (grades 0-5) and IMR, measured in the infarct-related artery after aspiration/balloon angioplasty has ...