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

Overview

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.

Fractional flow reserve (FFR) measurement by under hyperemic conditions has become the invasive gold standard for determining the physiologic extent of cardiac ischemia, and which has been validated in several clinical outcomes studies as a way of optimizing case selection for percutaneous coronary intervention (PCI). More recently in two large-scale randomized controlled trials using a non-hyperemic resting measurement, the instantaneous wave free ratio (iFR) showed non-inferiority in major adverse cardiovascular events (MACE) comparing iFR to FFR for physiological assessment of moderate coronary stenosis. FFR is calculated as the ratio of the distal coronary pressure to the aortic pressure (Pd/Pa) during maximal micro-circulatory relaxation. iFR is a diagnostic tool used to assess whether a stenosis is causing a limitation of blood flow in coronary arteries with subsequent ischemia. iFR is performed during cardiac catheterization (angiography) using invasive coronary pressure wires which are placed in the coronary arteries that are to be assessed. The iFR negates the time averaging and administration of vasodilators necessary for FFR by identifying from the resting pressure waveform a period when the native microcirculatory resistance is constant and minimized in diastole. The study is looking at the accuracy and precision of a novel adenosine-independent index of coronary artery stenosis, the resting flow reserve, against the instantaneous wave-free ratio and fractional flow reserve.