Clinical methods to determine coronary flow and myocardial perfusion.

In this overview, currently available clinical methods to measure flow in the coronary circulation will be discussed. Methods only applicable in the experimental laboratory or in the anaesthetized patient during cardiac surgery, will not be described. We distinguish between methods that measure global blood flow, and methods that determine regional flow, either at the level of the coronary arteries or at the level of the myocardium. Since it is difficult to measure coronary flow in absolute values, 'flow reserve' is often used as an alternative. Flow reserve is calculated by dividing maximal flow, usually pharmacologically induced, by basal flow. Consequently, assessment of flow reserve requires only measurements of relative changes of coronary flow. The applicability and relative merits and limitations of the techniques are discussed.