Reproducibility of a cardiac magnetic resonance derived myocardial perfusion reserve index

Myocardial perfusion imaging has an important and expanding role, predominantly in the management of patients with coronary artery disease. Cardiovascular magnetic resonance (CMR) perfusion imaging is particularly valuable as it does not use ionising radiation and is multiparametric—i.e., perfusion imaging is routinely combined with an assessment of myocardial structure, function and scar. Qualitative analysis of CMR perfusion images is the current clinical standard and this has repeatedly been shown to be accurate (1,2). However, quantification of perfusion should result in more reproducible and precise measurements and has potential advantages in a number of patient subsets. This includes patients with multivessel disease, where perfusion imaging frequently underestimates the number of ischaemic territories compared to invasive anatomic (3) and functional assessments (4), patients with left ventricular impairment and after CABG. Furthermore, quantification of perfusion may assist in the evaluation of patients with angina and normal epicardial coronary arteries, who are often poorly understood and managed.