Coronary artery bypass graft (CABG) surgery is the commonest type of heart operation performed. During this, arteries or veins (termed 'grafts') are used to supply blood around blockages within the blood vessels that supply the heart. Unfortunately, these grafts can sometimes fail, and patients can also experience complications like heart attacks and strokes, after surgery. It is known that vein grafts are more likely to narrow over time. Additionally, treating vein graft failure is very challenging, as repeat surgery is riskier and procedures to stent open the veins can also fail. However, it is not fully understood why these complications occur.

In this study, the investigators will use an imaging technique called a total-body Positron Emission Tomography (PET) scan. This uses special radioactive dyes (radiotracers) to look at what is happening inside vein grafts. With this technique, the investigators will also be able to see what is happening to the heart, brain and wider parts of the body after CABG surgery.

This study will aim to recruit 70 participants in total (maximum 150). 40 (maximum of 120) of these participants will have recently undergone CABG surgery and received ≥1 vein graft. The remaining 30 will have undergone CABG surgery ≥5 years ago and will have symptoms suggestive of vein graft failure.

The study will last a total of 36 months and will involve participants undertaking the following assessments:

1. Total-body Positron Emission Tomography and Computed Tomography (PET-CT) scan
2. Ultrasound scan of the heart (echocardiogram)
3. A blood test - up to four tablespoons (60 mL) of blood will be taken for immediate testing and the remainder will be stored for future ethically approved studies.

This is an observational cohort study investigating the role of inflammation, thrombosis and fibrosis in saphenous vein graft failure following CABG surgery. The presence and distribution of these processes will be examined in one cohort overtime (immediately following surgery and at 1 year-follow up) and at one time-point in a second cohort with clinically suspected vein graft failure.

Participants in both cohorts will undergo clinical review (including blood sampling), transthoracic echocardiogram and combined total-body positron emission tomography computed tomography (PET-CT) imaging, with CT coronary angiography.

INCLUSION CRITERIA:

Cohort 1: Patients undergoing CABG surgery

• Males and females over 18 years of age
• Patients undergoing CABG surgery for multivessel coronary artery disease, who receive at least one saphenous vein graft

Cohort 2: Patients with symptomatic saphenous vein graft vasculopathy

• Males and females over 18 years of age
• Patients who underwent CABG surgery ≥ 5 years prior to recruitment for multivessel disease and received 2 or more saphenous vein grafts
• Referred for invasive coronary angiography due to recurrent symptoms and with a high suspicion of graft vasculopathy

EXCLUSION CRITERIA:

• Patients with a life expectancy of < 2 years
• Renal failure (estimated glomerular filtration rate <30 mL/min/1.73 m2)
• Patients on immunosuppressive therapies
• Females of child-bearing age who are pregnant or breastfeeding,
• Known allergy or contraindications to iodinated contrast or radiotracer
• Patients who are unable to tolerate the supine position
• Patients who are unable to provide informed consent

We will recruit two populations of patients following CABG surgery. Participants will be prospectively recruited following CABG surgery (cohort 1), or identification of clinically suspected saphenous vein graft failure (cohort 2). Recruitment will for both cohorts will be from a single, tertiary centre (Royal Infirmary of Edinburgh).