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

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 catherization (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.

Inclusion Criteria:

1. Age ≥ 18 years.

2. Patient provides signed written informed consent before any study-specific procedure.

3. Undergoing coronary angiography, for silent ischemia, stable angina, acute coronary
syndrome, or other acceptable indication per the local standard of care.

4. Angiographically 40%-90% stenosis present in at least one native coronary artery.

5. Undergoing physiological assessment for standard clinical or diagnostic indications

Exclusion Criteria:

1. Aorto-ostial lesion location within 3 mm of the aorta junction (both right and left).

2. Left main stenosis

3. Vessel(s) and lesion(s) not amenable for percutaneous coronary intervention (PCI) ,
for example diffuse disease.

4. Saphenous vein graft, chronic total occlusion

5. Haemodynamic instability at the time of intervention (heart rate<50 beats per minute,
systolic blood pressure <90mmHg), balloon pump

6. Currently participating in another clinical study that interferes with study results.

7. Pregnant or nursing subjects and those who plan pregnancy in the period up to 1 year
following index procedure.

8. Any other medical condition that in the opinion of the investigator will interfere
with patient safety or study results.

9. High degree A-V block, sinus node disease.

10. Asthma/Chronic obstructive pulmonary disease (COPD) with active wheeze

11. Known hypersensitivity to adenosine

12. ST-Elevation Myocardial Infarction (STEMI) within 48 hours.