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Colour coded blood flow imaging in intravascular ultrasound

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A 42 year old man was admitted to our hospital with sudden chest pain. The exercise ECG showed inferior ST segment depression suggesting ischaemia. Coronary angiography revealed a normal left coronary artery and severe proximal stenosis of the right coronary artery. The patient underwent direct percutaneous transluminal coronary angioplasty with coronary stent–graft implantation. The stent–graft is a combination of a metal stent with a membrane of polytetrafluorethylene. Angiography suggested good stent apposition without residual stenosis. With standard intravascular ultrasound (IVUS) full stent expansion was assessed (A, large arrow: stent-graft; small arrow: lumen), revealing a weak signal distal of the stent caused by partial absorption of the ultrasound signal from the specific stent graft material. In contrast to angiography and standard IVUS, colour coded blood flow imaging revealed incomplete apposition in the proximal entrance of the stent graft in more than 50% of the circumference documented by blood flow (red) in the two dimensional image (B, arrows) plane as well as in the sagittal reconstruction of the vessel (C, arrows).

Colour coded blood flow imaging is a recently introduced and commercially available technique encoding the rate of change of the backscatter echo of the blood cells into colour. Since the ultrasound beam is identical to the one used in standard IVUS, the colour information is displayed simultaneously with the standard IVUS information. Flow between the stent and the vessel wall was documented only with colour coding, representing incomplete attachment of the stent to the vessel wall (B and C, arrows). Colour coded blood flow imaging is a useful adjunct to standard greyscale IVUS in specific lesions.