Visual assessment of a coronary artery narrowing (called stenosis) seen on angiography is conventionally used to infer how likely the stenosis will limit blood flow (called ischemia) under conditions of increased demand (e.g exercise). This is based on animal work and data from humans with simple single vessel disease with no co-existing conditions. These data have been extrapolated to more complex patients/ complex disease but clearly over-simplifies the situation in the majority of patients cardiologists treat.

Pivotal work by DeBruyne, Pils and colleagues in the 90's convincingly showed that pressure derived measurements, called FFR, from the coronary artery during a cardiac catheterization, more accurately identify stenoses that would cause ischemia compared to visual assessment alone. A strategy of FFR guided coronary stenting with drug eluting stents significantly improved outcomes and reduced costs compared to visual assessment alone (FAME trial). Deferring treatment based on FFR has been shown to be safe (DEFER Trial). FFR has excellent sensitivity and specificity. A FFR of <=0.80 was used as this identified ischemia causing lesions 90% of the time. Therefore, the concept of FFR guided percutaneous revascularisation and treatment deferral has a robust evidence base to support it.

Coronary bypass grafting (CABG) is traditionally based solely on a visual assessment of angiography images. SPY® Infrared Fluorescence Angiography (NIRF, FDA approved 2005) is used by some cardiac surgeons to assess the patency of bypass grafts in real-time in the operating room, as a surrogate for immediate traditional coronary angiography. Dr. Ferguson observed that regional myocardial perfusion (RMP) image data was also captured in these video sequences.

Study Hypotheses:

1. In patients who are likely CABG candidates, target vessel epicardial coronary arteries (TVECAs) with FFR > 0.80 will not demonstrate an increase in RMP despite an anatomically patent bypass conduit during SPY® imaging.
2. In TVECAs with an increase in RMP during SPY® imaging, cardiac catheter laboratory measures of coronary physiology from that TVECA, namely one or a combination of FFR, CFR, HSR and HMR, will correlate with the SPY® data on myocardial perfusion, and suggest a potential mechanism for this physiologic response to TVECA grafting.

Inclusion Criteria:

• Age >18<80
• Patients with stable angina or NSTEMI with total CK rise of <1000 U/litre who after planned coronary angiography are going to be referred for CABG and have at least one vessel with a visual 40-80% stenosis that is interrogated with intracoronary physiology

Exclusion Criteria:

• Emergent status, or Cardiogenic shock
• LVEF <40%
• History of actively malignant disease
• Patient needing concomitant valvular surgery or other cardiac structural reconstructive surgery
• As is standard of care, those vessels that are extremely tortuous, very small caliber and/or heavily calcified would not have such wires passed down them. Furthermore, those vessels that are 80-90+% stenosed, with \