Coronary artery bypass grafts and MDCT imaging: what to know and what to look for

CCTA in the diagnosis of coronary artery disease

The world of cardiac imaging is proposing to physicians an ever-increasing spectrum of options and tools with the disadvantages of patients presently submitted to multiple, sequential, time-consuming, and costly diagnostic procedures and tests, sometimes with contradicting results. In the last two decades, the CCTA has evolved into a valuable diagnostic test in today's patient care, changing the official existing guidelines and clinical practice with a pivotal role to exclude significant CAD, in the referral of patients to the Cath-Lab, in the follow-up after coronary revascularization, and finally in the cardiovascular risk stratification.

Diagnostic Accuracy of Dual-Source 64-Slice Multidetector Computed Tomography in Evaluation of Coronary Artery Bypass Grafts

Background

The aim of this study was to compare the diagnostic accuracy of 64-slice multidetector computed tomography (MDCT) with conventional coronary angiography to detect graft patency and stenosis.

Methods

In this retrospective analysis, we included a total of 284 subjects (210 men, 73.9%; mean ± SD age, 62.6 ± 9.9) and evaluated 684 bypass grafts using a dual-source 64-slice MDCT scanner The mean ± SD time interval between coronary artery bypass grafting operation and MDCT was 30.8 ± 6.2 months. The mean ± SD interval between MDCT angiography and conventional coronary angiography was 14.2 ± 3.6 days. Significant stenosis was defined as lesions causing 50% or greater luminal narrowing. All atherosclerotic lesion components were assessed on per-segment basis.

Results

All of the 684 grafts (420 venous and 264 arterial grafts) were evaluable and included in the analysis. For the detection of 50% or greater graft stenosis, the sensitivity, specificity, positive predictive value and negative predictive value of MDCT was 98.3%, 99.3%, 98.3%, and 99.3% for venous grafts and 100%, 99.5%, 98.0%, and 100% for arterial grafts. In detection of graft patency, the sensitivity, specificity, positive predictive value, and negative predictive value of MDCT was 99.6%, 97.2%, 99.0%, and 99.0% for venous grafts and 99.5%, 97.5%, 99.5%, and 97.5% for arterial grafts. Diagnostic accuracy for the detection of graft patency was 99% (416/420) and 99.2% (262/264) for venous and arterial grafts, respectively.

Conclusion

The diagnostic accuracy of dual-source 64-slice MDCT angiography for evaluating coronary artery bypass grafts patency and stenosis was high. Dual-source 64-slice MDCT can be used for the evaluation of patients after coronary artery bypass grafting.

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.

Automatic MDCT injectors: hygiene and efficiency of disposable, prefilled, and multidosing roller pump systems in clinical routine

OBJECTIVE

This study evaluated three different injection systems with regard to microbiological contamination, time efficiency, and user handling during a clinical routine.

SUBJECTS AND METHODS

A total of 825 patients were included. A double-syringe contrast injector with disposable syringes (system A; n = 150) and one that used prefilled syringes (system B; n = 150) were microbiologically analyzed during single use of the syringes in one patient. Moreover, the contamination of a roller pump injector capable of multidosing several patients from a contrast agent container, without the need for prior filling, was determined after being used for an entire day (system C; n = 35 injections/day for 15 days). The hygienic background was guaranteed by taking imprints of the surfaces of devices and the palms of the hands of members of CT staff before the clinical investigation. The time required for assembly of the injection systems and for filling or refilling of each injector system was measured. The handling of the three systems also was subjectively ranked by the technicians.

RESULTS

Injection systems A, B, and C remained microbiologically sterile and free of contamination throughout their use in clinical routine. The mean (± SD) time for injection system assembly and installation of syringes and filling did not differ significantly between injection systems A and B (system A, 2.5 ± 1.1 minutes; system B, 1.9 ± 1.3 minutes; p = 0.12), whereas the time for assembly of system C was significantly shorter (0.9 ± 0.6 minutes; p < 0.05 vs system A; p < 0.05 vs system B). In the subjective ranking of injector handling, systems B and C were preferred.

CONCLUSION

Double-syringe injectors used with disposable or prefilled contrast agent syringes, as well as roller pump injectors, ensure hygienic conditions in clinical routine. However, time efficiency and handling are aspects that favor prefilled and roller pump systems.

Diagnostic performance of 320-slice multidetector computed tomography coronary angiography in patients after coronary artery bypass grafting

Objectives

To evaluate the diagnostic performance of 320-slice computed tomography coronary angiography (CTA) in the evaluation of patients with prior coronary artery bypass grafting (CABG). Invasive coronary angiography (ICA) served as the standard of reference, using a quantitative approach.

Methods

CTA studies were performed using CT equipment with 320 detector-rows, each 0.5 mm wide, and a gantry rotation time of 0.35 s. All grafts, recipient and nongrafted vessels were deemed interpretable or uninterpretable. The presence of significant (≥50%) stenosis and occlusion were determined on vessel and patient basis. Results were compared to ICA using quantitative coronary angiography.

Results

A total of 40 patients (28 men, 76 ± 15 years), with 89 grafts, were included in the study. On a graft analysis, the sensitivity, specificity, positive and negative predictive values in the evaluation of significant stenosis were 96%, 92%, 83% and 98% respectively. The diagnostic accuracy for the assessment of recipient and nongrafted vessels was 89% and 80%, respectively. The diagnostic accuracy for the assessment of graft, recipient and nongrafted vessel occlusion was 96%, 92% and 100%, respectively.

Conclusions

320-slice CTA allows accurate non-invasive assessment of significant graft, recipient vessel and nongrafted vessel stenosis in patients with prior CABG.

Coronary artery graft dilatation aided by multidetector computed tomography

Coronary angiography is the standard method of follow-up for patients with coronary artery bypass grafts, but it is an invasive and costly procedure that is not risk-free. Recently, 64-slice multidetector computed tomography has allowed reliable visualization of coronary artery grafts and their anastomotic status, with high spatial resolution. We describe a successful case of percutaneous coronary intervention for occluded coronary artery bypass grafts with the aid of multidetector computed tomography.

Radiation dose reduction in computed tomography: techniques and future perspective

Despite universal consensus that computed tomography (CT) overwhelmingly benefits patients when used for appropriate indications, concerns have been raised regarding the potential risk of cancer induction from CT due to the exponentially increased use of CT in medicine. Keeping radiation dose as low as reasonably achievable, consistent with the diagnostic task, remains the most important strategy for decreasing this potential risk. This article summarizes the general technical strategies that are commonly used for radiation dose management in CT. Dose-management strategies for pediatric CT, cardiac CT, dual-energy CT, CT perfusion and interventional CT are specifically discussed, and future perspectives on CT dose reduction are presented.

Prospectively gated axial CT coronary angiography: preliminary experiences with a novel low-dose technique

To assess image quality and radiation exposure with prospectively gated axial CT coronary angiography (PGA) compared to retrospectively gated helical techniques (RGH). Forty patients with suspected coronary artery disease (CAD) and a stable heart rate below 65 bpm underwent CT coronary angiography (CTCA) using a 64-channel CT system. The patient cohort consisted of 20 consecutive patients examined using a PGA technique and 20 patients examined using a standard RGH technique. Both groups were matched demographically according to age, gender, body mass index, and heart rate. For both groups, two independent observers assessed image quality for all coronary segments on an ordinal scale from 1 (nonassessable) to 5 (excellent quality). Image quality and radiation exposure were compared between patient groups. There were no significant differences in vessel-based image quality between the two groups (P > 0.05). Mean (+/- SD) effective radiation exposure in the PGA group was 3.7 +/- 0.8 mSv compared to 18.9 +/- 3.8 mSv in the RGH group without ECG-based tube current modulation (P < 0.001). Preliminary experience shows PGA technique to be a promising approach for CTCA resulting in a substantial reduction in radiation exposure with image quality comparable to that of standard RGH technique.