Ischaemia clinical trials

Visual Estimation of Coronary Fractional Flow Reserve From High-definition Computed Tomographic Coronary Angiography

The identification of abnormal narrowing of a blood vessel from non-invasive coronary angiography remains an exciting goal. While Computed Tomography (CT) has established a clear role in patients it retains some limitations. Primarily, alterations in blood flow leading to a restriction in blood supply to tissues cannot be accurately predicted from the anatomical assessment of an abnormal narrowing in a blood vessel - a limitation of both invasive, and computed tomographic, angiography. This is important, as there is now a raft of evidence demonstrating that revascularisation should only be considered in the presence of a restriction in blood supply to tissues. The gold standard method of identifying a restriction in blood supply to tissues is measurement of the fractional flow reserve (FFR), a dimensionless value generated as a ratio between the circulatory pressure before and after a narrowing of a blood vessel. At present, patients with indeterminately significant abnormal narrowing in a blood vessel identified using CT must go on to have a further test for a restriction in blood supply to tissues, prior to any decision about revascularisation being made. As part of our governance commitment to maintaining our reporting standards, we undertake ongoing audit of our cardiac CT practice. The investigators recently identified a group of patients who have undergone FFR measurement as part of routine clinical care, and compared these to our clinical reports, to ensure that appropriate recommendations were being made. It appeared that the ability to predict important abnormal narrowing in a blood vessel was reasonable (~70%) and hence we propose the formulation of a research question to explore this further. The primary objective of this study is to determine the accuracy of a visual assessment of the likely significance on blood flow of a narrowing of a blood vessel identified on cardiac CT, in comparison to invasive, fractional flow reserve. The secondary objective is to evaluate features of an abnormal narrowing in a blood vessel that is likely to have a significant impact on blood flow. The investigators' working hypothesis is that cardiac CT FFR is a useful predictor of abnormal narrowing in a blood vessel.