Narrowing of coronary arteries interferes with blood flow and can cause chest pain. Cardiologists sometimes quantify the extent of the narrowing by measuring the fractional flow reserve (the ratio of the pressure in the aorta to the pressure downstream of the narrowing under conditions of maximal flow). We propose a new technique based on principles of wave intensity analysis (WIA) to better assess coronary stenosis and the significance of the narrowing without the need for administration of vasodilator agents such as adenosine. This would simplify assessment and improve our ability to advise patients whether stent treatment will help their symptoms.