Stenoses Clinical Trial
Official title:
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.
This is a retrospective study of diagnostic accuracy. We do not intend to undertake any
intervention or require patient involvement at any stage of this research.
The study would utilise anonymised patient data, identified as part of the previous audit.
FFR values are already known for each patient. The image dataset would be retrieved and
matched to an FFR. At this stage all data, including the images, would be anonymised. The
images would be reviewed independently by two expert readers who would record their
impression of the likely haemodynamic significance of a particular stenosis. Two weeks
later, to minimise bias, the readers would re-review the images to identify features of the
stenoses known, or likely, to cause haemodynamic significance, including stenosis length,
territory of the vessel, calcification.
The results would be directly compared to the FFR readings and the features would be
subjected to multivariate analysis to identify any salient anatomical feature which may
predict haemodynamic significance.
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Observational Model: Cohort, Time Perspective: Retrospective
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