Evidence based medicine: role of multidetector CT in the follow-up of patients receiving coronary artery bypass graft

Computerized tomography may underestimate the patency of internal thoracic artery composite grafts

BACKGROUND

Multidetector-row computerized tomography (MDCT) has been regarded as useful for noninvasive assessment of the bypass grafts after coronary artery bypass grafting (CABG), but there have been few reports validating its accuracy in assessment of composite arterial graft patency.

METHODS

In 108 patients who underwent CABG with a Y-composite graft made of bilateral internal thoracic arteries (ITAs), early postoperative (mean interval, 4.9 months) MDCT findings were compared with the findings of subsequent conventional coronary angiography (19 patients, mean 4.7 months after initial MDCT) or later MDCT (89 patients, mean 31.0 months after surgery). A total of 248 grafts with 409 distal anastomoses (mean 3.8/patient) were assessed.

RESULTS

In the early MDCT, the left ITA was patent in 94.4%. The right ITA with multiple sequential anastomoses was completely patent in 73.8% and partially patent in 21.4%. Discrepancy of findings between early computed tomography (CT) and later imaging studies was found in 18 patients (16.7%). Fourteen (42.4%, 4 left and 10 right ITAs) among the 33 initially nonvisualized grafts showed improved patency in later MDCT or conventional angiogram. The positive predictive value of the early MDCT for ITA composite graft occlusion was calculated at 57.6% or lower, whereas the negative predictive value was 97.8% or higher.

CONCLUSIONS

For a composite graft made of bilateral ITAs, especially for those with multiple sequential anastomoses, MDCT may reflect only the functional patency and underestimate the actual anatomic patency.

Diagnostic accuracy of 64-slice CT in evaluating coronary artery bypass grafts and of the native coronary arteries

PURPOSE

Our aim was to evaluate the accuracy, sensitivity and specificity of 64-slice multidetector computed tomography (MDCT) in the assessment of occlusions and stenoses of arterial and venous bypass grafts and disease progression in the native vessels distal to the graft, and to compare the results with those of conventional coronary angiography.

MATERIALS AND METHODS

We enrolled 78 individuals (45 men, 33 women; mean age 59) and evaluated 213 bypass grafts using a 64-slice MDCT scanner. All patients underwent conventional coronary angiography with a mean time interval between the two examinations of 2 days.

RESULTS

One patient was excluded due to arrhythmia during the examination. The 212 bypass grafts in the remaining 77 patients (98.7%) consisted of 115 (54%) venous grafts and 97 (46%) arterial grafts. In the 115 venous grafts, MDCT showed a sensitivity, specificity and accuracy of 100% in evaluating occluded grafts and a sensitivity of 94.4%, specificity of 98.4% and accuracy of 96.9% in evaluating significant stenoses. In evaluating occluded arterial grafts, sensitivity was 83.3%, specificity 100% and accuracy 98.9%, whereas in evaluating stenoses of arterial grafts, sensitivity was 100%, specificity 97.7% and accuracy 98%.

CONCLUSIONS

Sensitivity, specificity and accuracy in evaluating native coronary vessels distal to the graft allow for a complete assessment of the surgical and native circulation. The examination appears therefore to be exhaustive in ruling out or confirming the presence of diseased vessels in the postoperative follow-up.

[Multidetector computed tomography coronarography: preliminary experience in real life settings]

Multidetector computed tomography coronarography (MDCT) is a promising tool, offering non invasive anatomic evaluation of coronary arteries. We relate in this article our impressions after our first two years experience.

METHODS

Retrospective study of the 328 patients who underwent MDCT examination between January 2005 and December 2006 at our community hospital. Per patient comparative analysis of the anatomical findings versus percutaneous angiography (PCA) in 61 cases.

RESULTS

Out of 328 patients 61 (18.5%) underwent PCA. In these patients we found a sensibility, specificity, positive predictive value and negative predictive value of 100%, 54%, 59% and 100% for MDCT. The main factor responsible for inconclusive vessel analysis was excessive calcification.

CONCLUSION

In routine use, MDCT enables one to rule out significant stenosis non invasively, with high sensitivity in an unselected patient population.