Defining the haemodynamic significance of a stenosis by visual assessment from the angiogram is difficult. It frequently appears that a stenosis which is not clearly related to symptoms is treated, even if ischaemia can not be attributed to the lesion and even if the stenosis is only of mild or moderate severity.
1,2 One of the methods to define the pathophysiological significance of an intermediate stenosis (diameter stenosis of 50 to 70%) is the determination of the fractional flow reserve (FFR). The FFR is defined as the ratio of maximal blood flow achievable in a stenotic coronary artery relative to the maximal flow in the same artery if it were normal. Its normal value is 1.0 and a value of <0.75 identifies lesions which are associated with inducible ischaemia with a high diagnostic accuracy.
3 Many studies have demonstrated the safety of deferring revascularisation in patients with moderate coronary stenosis based on FFR results of ≥0.75.
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