Patients at high risk of having one or more coronary stenosis are evaluated routinely by invasive coronary angiography (CAG). Lesions are often quantified by QCA, but fractional flow reserve is increasingly used to assess functional significance of identified stenosis. FFR is assessed during CAG by advancing a wire with a pressure transducer towards the stenosis and measure the ratio in pressure between the two sides of the stenosis during medical induced maximum blood flow (hyperaemia).