Title: The BYPASS-CTCA Study: A Randomised controlled trial assessing the value of Computed Tomography Cardiac Angiography (CTCA) in reducing procedure duration, limiting post-procedural kidney damage and improving patient satisfaction in patients who had previous bypass operation undergoing invasive coronary angiography (ICA)
Funder: Department of Health and Social Care

Abstract: Background: Coronary angiography is frequently required after coronary artery bypass graft (CABG) surgery because of graft failure or the progression of native coronary artery atherosclerosis. Indeed, the natural history of bypass grafts is such that 10&ndash;15% of venous grafts are occluded per year, with 50% occluded after a period of 10 years. Coronary angiography can be challenging in such patients, especially when the CABG anatomy is unknown at the time of catheterization; therefore coronary angiography in CABG patients lasts longer, leads to higher irradiation, more nephrotoxicity, is often performed femorally (increasing vascular complications) and is associated with a greater number of complications (stroke, bleeding) than in patients without CABG. Contrast induced nephropathy (CIN) (acute kidney injury resulting from the administration of iodinated contrast media) is a complex disorder characterised by early (within hours or days of the procedure) worsening of renal function, with clinical manifestations ranging from minimal increase in serum creatinine to anuric renal failure requiring renal replacement therapy. Two of the major predictors of CIN are the amount of contrast administered and multi-vessel disease, both important issues in patients with previous CABG meaning CIN is a major problem in this patient cohort, with rates double that seen in patients without previous CABG. Computerised Tomography Coronary Angiography (CTCA) has emerged as a useful clinical tool in CABG assessment over the last decade. Technical advances mean new 3rd generation dual source CT scanners can visualise bypass grafts with minimal contrast (30mls), time ( Research Hypothesis and Aims: The study aims to evaluate the efficacy of upfront CTCA prior to coronary angiography to improve patient satisfaction, reduce contrast load, procedural duration, and procedural complications specifically CIN compared to coronary angiography alone. Plan of Investigation: The BYPASS-CTCA Study is a single center, randomized clinical trial, which plans to recruit 688 patients with previous CABG undergoing invasive coronary procedures that involve the administration of intracoronary iodinated contrast media (angiography+/-PCI). It is designed to ascertain whether CTCA might prove useful adjunctive therapy reducing angiography procedure time, improving patient satisfaction, and reducing rates of post-procedural renal dysfunction (CIN). The primary endpoints will be multifactorial 1). Procedure duration, 2). The incidence of CIN, as defined by KDIGO criteria post angiography and 3). Patient satisfaction with angiography. Key secondary endpoints will be whether CTCA impacts upon procedural contrast volume, complications (dissection, stroke, vascular access complications), radiation dose, and the number of catheters used during the coronary angiogram. An economic evaluation will be performed with an incremental cost per quality-adjusted life year (QALY) gained, calculated using quality of life data obatined over a 12 month follow-up period. Follow-up data will be collected via telephone or an internet based Patient reported outcome measures (PROMS) application. Benefits: This trial if positive, will identify a new, safe and easy to deliver diagnostic tool for patients with previous CABG prior to often difficult coronary angiographic procedures. Studies suggest that within 3 years of CABG 1 in 5 patients have required further coronary angiography, resulting in a large currently unmet need to improve this procedure. This study could potentially influence future clinical practice guidelines and provide the NHS with an option to improve the experience and outcomes of patients with previous CABG undergoing invasive coronary angiographic procedures.

Lay abstract: Many people suffer from angina (chest pain, which comes on with exertion and is relieved by rest), caused by narrowing s in the coronary arteries, visualised by a special X-ray-based examination called a coronary angiogram. Angina can be treated with an operation in which the narrowings are bypassed, otherwise known as a coronary artery bypass graft (CABG). The problem is that over time these bypasses can narrow and block, therefore these patients often redevelop chest pain and require further coronary angiograms. For patients with previous bypasses, coronary angiography procedures can lead to a number of complications. Procedures may last longer, lead to higher doses of radiation and higher contrast (x-ray dye) volumes which can be associated with kidney damage. This is because the placements of the grafts vary and therefore it can take longer to find them, subjecting patients to greater risks and more discomfort. Computerised Tomography Coronary Angiography (CTCA) involves using a CT scan to identify coronary artery narrowings. It has considerably fewer risks than coronary angiography and is very accurate at identifying the location of and blockages in bypass grafts. However, although the ability of CTCA to detect the position and patency of bypass grafts is well known, it is unclear whether this scan leads to safer coronary angiography. This research will assess 688 patients with previous bypasses who are due to undergo coronary angiography. The aim is to see if the CT scan before the procedure can make angiography safer, shorter and more comfortable for the patient. Patients who are suitable will be allocated to either receive CTCA as part of their assessment or receive standard assessment without this test. Patient satisfaction with the tests, dye/radiation amount, procedure duration, complications and importantly kidney damage will all be recorded and compared between the two groups.

Research activity codes: 6.4 SURGERY;4.2 EVALUATION OF MARKERS AND TECHNOLOGIES
Health categories: RENAL AND UROGENITAL;CARDIOVASCULAR