Radiological methods
This was performed using a Somatom Flash dual-source CT scanner
(Siemens, Erlangen, Germany). All subjects received 0.25 mg of
Nitroglycerin sublingually. Those with a heart frequency
>70 beats/minute and no contraindications were also given
up to 10 mg of Metoprolol intravenously before the examination. Contrast
media (60-70 ml Iomeron 400 mg/ml, Bracco, Milan, Italy) was
administered with a pressure injector at a flow rate of 6 ml/second,
followed by a bolus of 60 ml saline. Scanning started at the left
subclavian artery and ended at the base of the heart. The images were
reviewed at a Siemens SyngoVia workstation. All images were
independently reviewed by two thoracic radiologists who were blinded to
group assignment. Disagreements were resolved by consensus. A graft was
judged as occluded when the graft was not opacified by contrast media. A
graft stenosis was judged as significant when the narrowing of the lumen
diameter was > 50% relative to the adjacent parts of the
vessel.