The shortcomings of coronary arteriography to assess the physiological significance of coronary stenoses have been recognised for decades1 ,2; therefore, the importance of additional physiological techniques is beyond doubt. One of the currently available physiological techniques is coronary pressure measurement, which has emerged over the past few years as a major step forward in the invasive assessment of coronary artery disease.3-9This was partly owing to major technical progress in developing pressure monitoring guidewires and partly to a theoretical innovation, the concept of coronary pressure derived fractional flow reserve (FFR), which closely relates distal coronary pressure to myocardial blood flow during maximum arteriolar vasodilatation. In the catheterisation laboratory, this new approach enables an “on the spot” diagnosis as to what extent a given epicardial stenosis contributes to reversible myocardial ischaemia and the decision whether revascularisation of the stenosis is warranted. In addition, pressure derived FFR appears to be a useful index to monitor and guide coronary intervention, particularly adequate stent deployment.10 ,11

This review aims to provide a short overview of the theoretical and physiological background of this new approach and to focus on its clinical applicability, both for diagnostic and therapeutic catheterisation.