fractional flow reserve (FFR)


Established measures of coronary physiology. 

The fractional flow reserve (FFR) is an index of epicardial 

coronary physiology and is measured during maximal 

hyperemia. The coronary flow reserve (CR) is a measure 

of both the epicardial and microvascular physiology and is 

expressed as the ratio of hyperemic to basal flow, simplified to the ratio of basal to hyperemic mean transit time. 

The index of microcirculatory resistance (IMR) is a spe- 

cific index of the microcirculation and is expressed as the 

product of Pd and mean transit time. Pw here indicates the 

coronary wedge pressure. 


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