Effects of Postoperative Pericardial Effusion on Coronary Artery Bypass Grafts: A Study with X-ray Computed...

The aim of this study was to evaluate the effects of pericardial effusion on coronary artery bypass grafts and their patency using X-ray computed tomography (CT). Uncontrasted CT of horizontal sections from the lower margin of the aortic arch to the left ventricle was done at 5-mm intervals. In one cross-section of the pulmonary bifurcation level, 30 ml of a contrast media (lohexol 350) was injected at a rate of 3 ml/second into the antecubital vein. All slices of uncontrasted CT were analyzed for the presence or absence of effusion. The severity was expressed as the maximum value of the thickness of effusion. CT was repeated about every 6 months postoperatively under the same conditions. Selective angiography was also performed 7.1 +/- 3.9 months postoperatively. A total of 46 patients (mean age 57 years) underwent CT and angiography. A total of 95 grafts were implanted: 90 saphenous veins and 5 internal thoracic arteries. Selective angiography revealed that 79 grafts were patent and 16 were occluded. The first postoperative CT (at 2.6 +/- 2.1 months) showed the retention of effusion in all patients. The mean maximum value was 1.0 +/- 0.5 cm; there were no significant differences between patent grafts (1.0 +/- 0.5 cm) and occluded grafts (1.0 +/- 0.5 cm). Occlusion was found in 10 grafts by the first CT (2.9 +/- 2.7 months postoperatively) and another 6 grafts by the second CT (11.3 +/- 4.2 months). Thereafter, all grafts were patent. Previously occluded grafts showed no cross-section images on uncontrasted or contrasted CT. Except for two grafts, all patent grafts could be observed even without contrast enhancement. The remaining two grafts were masked with effusion, but patency was confirmed by a contrast media. In conclusion, retention of effusion does not affect the patency of grafts. Occlusion occurs early after surgery, and grafts cannot be imaged on CT. Patent grafts can be observed by uncontrasted CT, as well as contrasted CT, except where a large amount of effusion is present.