The index of microcirculatory resistance (IMR) in takotsubo cardiomyopathy.

We report a patient who presents with acute chest pain and positive cardiac enzymes clinically consistent with an acute coronary syndrome (ACS). Coronary angiography revealed normal epicardial arteries and the left ventriculogram was notable for apical ballooning. This was strongly suggestive of takotsubo cardiomyopathy. Pressure wire measurements of Fractional flow reserve (FFR) and IMR demonstrated a normal FFR, but significant microcirculatory dysfunction. This is the first such case that documents this abnormality invasively using the IMR, which unlike CFR is specific for the microcirculation and reproducible through a range of hemodynamic states.