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[Assessment of coronary artery bypass grafts by X-ray computed tomography with and without contrast enhancement]
1Department of Cardiology, JR Tokyo General Hospital.
Insights
Plain computed tomography (CT) without contrast enhancement effectively assesses coronary artery bypass graft patency. Time-density curves from CT do not predict graft flow volume.
Area of Science:
- Cardiovascular Imaging
- Radiology
- Surgical Assessment
Background:
- Coronary artery bypass grafting (CABG) requires reliable postoperative assessment of graft patency.
- X-ray computed tomography (CT) is a potential imaging modality for evaluating CABG grafts.
Purpose of the Study:
- To evaluate the efficacy of X-ray computed tomography (CT) with and without contrast enhancement for assessing coronary artery bypass graft patency.
- To determine if time-density curves (TDCs) derived from CT can predict graft flow volume.
Main Methods:
- Sixty-three coronary artery bypass grafts in 32 patients were assessed using CT.
- CT scans were performed both without contrast enhancement and with contrast enhancement following intravenous injection.
- Time-density curves (TDCs) were generated and compared with intraoperative electromagnetic flow meter (EMF) data.
Main Results:
- Angiography confirmed 50 patent grafts.
- Plain CT without contrast enhancement accurately identified patent grafts (sensitivity: 88%, specificity: 100%, accuracy: 91%).
- TDCs derived from CT did not correlate with graft flow volumes measured by EMF; occluded grafts were not visualized.
Conclusions:
- Plain CT without contrast enhancement is a valuable tool for assessing coronary artery bypass graft patency.
- CT-derived time-density curves are not useful for predicting graft flow in these grafts.
Abstract:
To assess the patency of coronary artery bypass grafts, we tested the capability of X-ray computed tomography (CT) with and without contrast enhancement. This procedure was used on 63 grafts (30 in the LAD; 20 in the LCX; 13 in the RCA) in 32 patients with a mean age of 56 +/- 8 years, all of whom were referred to our department for postoperative management or evaluation. The CT scanner used was Toshiba TCT-60A with a scan time of 3 sec, 5 mm thick slices, and 512 x 512 pixels. CT scans without contrast enhancement were obtained from the level of the aortic arch to the left ventricle. Eight sec after 30 ml of contrast media was injected at a rate of 3 ml/sec into an antecubital vein, 5 scans were made at the same level of the pulmonary artery truncus. After positioning the regions of interests on the ascending aorta and grafts, we obtained time-density curves (TDCs) and compared the data with those recorded from an intraoperative electromagnetic flow meter (EMF). Fifty grafts were angiographically patent. The appearance time, build-up time, peak time, disappearance time and peak densities obtained from TDCs of grafts did not correlate with the flow volumes measured by EMF. Patent grafts were easily identified visually, without contrast enhancement (sensitivity; 88%, specificity; 100%, accuracy; 91%). Occluded grafts were not imaged on CT, either with or without contrast enhancement. We concluded that the TDCs of grafts obtained by CT are of no value for predicting the graft flow, and that plain CT without contrast enhancement is sufficiently useful for assessing the patency of such grafts.