Assessing flow limitation in patients with stable coronary artery disease

Appropriate use of revascularisation in stable angina depends on cardiologists being able to discriminate flow limiting coronary atherosclerotic lesions from those that are merely bystanders. Invasive angiography has been used for this purpose for many years but is problematic because it is an anatomical assessment of a physiological property. Assessment of lesions by eye or quantitative measurement is known to be inaccurate.1 But studies over the past decade have shown that flow limitation can be accurately assessed by using a pressure wire to measure fractional flow reserve (FFR)—the ratio of distal to proximal pressures during maximal hyperaemia induced by adenosine infusion.

When validated against non-invasive stress testing, a threshold FFR of 0.75 was found to discriminate ischaemic from non-ischaemic flow limitation, although to maximise sensitivity a value of 0.8 is usually used in practice.2 In the Defer study, published in 2007, risk of death or myocardial infarction was less than 1% a year (over five years) among …