Anatomy and physiology of coronary blood flow

Regional myocardial blood flow can now be measured noninvasively in units of milliliters blood per minute per gram myocardium. These noninvasive measurements are not confined to a specific imaging modality but are available with MRI, CT, and PET, although, thus far, most investigations of the coronary circulation in humans have employed PET flow measurements. Flow estimates with these different imaging modalities were found in animal experiments to correlate well with invasive flow estimates by the arterial blood sampling-microsphere technique widely considered as the “gold standard” of flow measurements. 1 - 11 In these comparison studies, noninvasively-derived estimates corresponded linearly with invasively-measured myocardial blood flows over a wide flow range, i.e., from as low as 0.3 mL/minute/g to as high as 5-6 mL/minute/g. When tested in the human heart, noninvasive flow estimates correlated well with those obtained through invasively-obtained indices of flow and its changes by well-established alternate measurement approaches. 12 - 16 Development and commercial availability of user-friendly software programs have facilitated the use of these new measurement capabilities so that they are now readily available in the clinical environment for the study of patients with cardiovascular disease.