Novel Adenosine-independent Index of Coronary Artery Stenosis Severity Resting Flow Reserve

This study will enroll patients who are referred for coronary angiography and require physiological assessment to see if the lesion can be treated as per the local standard of care. Approximately 92 participants will be enrolled. There are no follow up visits required so participation in this study will end when subjects are discharged from the hospital.The study will be comparing the resting flow reserve against the instantaneous wave-free ratio (iFR) and fractional flow reserve. All these tests offer a way to image a legion and determine if it is suitable to be treated. FFR measures the pressure differences across (narrowed coronary arteries usually due to atherosclerosis), iFR's are performed during cardiac catheterisation (angiography) using invasive coronary pressure wires which are placed in the arteries of the heart that are to be assessed and the Resting flow reserve looks at the maximum increase in blood flow through the coronary arteries above the normal resting volume.