Diagnostic Performance of 64-Slice Computed Tomography in Evaluation of Coronary Artery Bypass Grafts

The effect of CTCA guided selective invasive graft assessment on coronary angiographic parameters and outcomes: Insights from the BYPASS-CTCA trial

BACKGROUND

Computed tomography cardiac angiography (CTCA) is recommended for the evaluation of patients with prior coronary artery bypass graft (CABG) surgery. The BYPASS-CTCA study demonstrated that CTCA prior to invasive coronary angiography (ICA) in CABG patients leads to significant reductions in procedure time and contrast-induced nephropathy (CIN), alongside improved patient satisfaction. However, whether CTCA information was used to facilitate selective graft cannulation at ICA was not protocol mandated. In this post-hoc analysis we investigated the influence of CTCA facilitated selective graft assessment on angiographic parameters and study endpoints.

METHODS

BYPASS-CTCA was a randomized controlled trial in which patients with previous CABG referred for ICA were randomized to undergo CTCA prior to ICA, or ICA alone. In this post-hoc analysis we assessed the impact of selective ICA (grafts not invasively cannulated based on the CTCA result) following CTCA versus non-selective ICA (imaging all grafts irrespective of CTCA findings). The primary endpoints were ICA procedural duration, incidence of CIN, and patient satisfaction post-ICA. Secondary endpoints included the incidence of procedural complications and 1-year major adverse cardiac events.

RESULTS

In the CTCA cohort (n ​= ​343), 214 (62.4%) patients had selective coronary angiography performed, whereas 129 (37.6%) patients had non-selective ICA. Procedure times were significantly reduced in the selective CTCA ​+ ​ICA group compared to the non-selective CTCA ​+ ​ICA group (-5.82min, 95% CI -7.99 to -3.65, p ​< ​0.001) along with reduction of CIN (1.5% vs 5.8%, OR 0.26, 95% CI 0.10 to 0.98). No difference was seen in patient satisfaction with the ICA, however procedural complications (0.9% vs 4.7%, OR 0.21, 95% CI 0.09-0.87) and 1-year major adverse cardiac events (13.1% vs 20.9%, HR 0.55, 95% CI 0.32-0.96) were significantly lower in the selective group.

CONCLUSIONS

In patients with prior CABG, CTCA guided selective angiographic assessment of bypass grafts is associated with improved procedural parameters, lower complication rates and better 12-month outcomes. Taken in addition to the main findings of the BYPASS-CTCA trial, these results suggest a synergistic approach between CTCA and ICA should be considered in this patient group.

REGISTRATION

ClinicalTrials.gov, NCT03736018.

A systematic review and meta-analysis of multidetector computed tomography in the assessment of coronary artery bypass grafts

PURPOSE

The present meta-analysis aimed to compare the diagnostic accuracy of more recent computed tomography coronary angiography (CTCA) with invasive coronary angiography (ICA) in the assessment of graft patency after coronary artery bypass graft surgery (CABG).

MATERIAL AND METHODS

A systematic review was performed using nine electronic databases from their dates of inception to July 2015. Predefined inclusion criteria included studies reporting on comparative outcomes using ≥64 slice multidetector computed tomography (MDCT) and ICA. The primary endpoints included graft occlusion and significant graft stenosis ≥50%. Secondary analyses included the comparison of arterial versus venous graft conduits, and the use of different MDCT techniques.

RESULTS

Thirty-one studies were identified according to selection criteria, involving 1975 patients with 5364 assessed grafts. Combined assessment of stenosis and occlusion for all grafts demonstrated a sensitivity of 96.1% [95% confidence interval (CI) 94.3-97.4%] and specificity of 96.3% (95% CI 95.1-97.3%). CTCA assessment of venous grafts demonstrated higher sensitivity compared to arterial grafts, when testing for both occlusion and stenosis (97.6% vs 89.2%, p=0.004).

CONCLUSION

Results of this study demonstrated that CTCA had a relatively high pooled sensitivity, specificity and negative predictive value compared to ICA. However, patient baseline characteristics varied between studies, and the results should be interpreted with caution. Nonetheless, our results indicate that CTCA should be recognized as an accurate and non-invasive investigation for graft patency in symptomatic patients after CABG.

Diagnostic accuracy and effective radiation dose of high pitch dual source multidetector computed tomography in evaluation of coronary artery bypass graft patency

OBJECTIVE

The aim of the study was to evaluate the diagnostic accuracy and effective radiation dose (ERD) of high pitch dual source multidetector computed tomography (MDCT) for coronary artery bypass graft (CABG) patency.

MATERIALS AND METHODS

Fourty-five patients who underwent 128 × 2‑slice MDCT angiography with a prospective electrocardiogram-triggering, low-dose, high pitch, dual source, flash spiral acquisition mode after CABG surgery were included in the study. The interobserver agreement of the image quality was evaluated with Cohen κ value. The image quality was compared to the heart rates (HRs) using Mann-Whitney U test and to the graft segments using χ(2) test. The findings for the CABG patency on MDCT were compared to those determined on catheter coronary angiography. Dose-length product (DLP) and ERD were compared to the gender, HRs, and body mass index (BMI) of the patients using Kruskall Wallis and Mann-Whitney U tests.

RESULTS

A total of 110 grafts and 330 vessel segments were evaluated with a good interobserver agreement (κ = 0.80). The image quality was better in proximal and middle graft segments (p < 0.05), as well as in the patients with low HRs (p < 0.05). High pitch MDCT had the following sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy for evaluation of graft patency: 92.8, 99.3, 92.8, 99.3 and 98.8 %, respectively. ERD was correlated to the HRs and BMI.

CONCLUSIONS

High pitch 128 × 2‑slice dual source CT angiography is a noninvasive imaging modality, and it can be safely and effectively used in evaluation of CABG patency with lower radiation dose.

256-slice CT angiographic evaluation of coronary artery bypass grafts: effect of heart rate, heart rate variability and Z-axis location on image quality

Purpose

The objective of this study is to assess the effect of heart rate, heart rate variability and z-axis location on coronary artery bypass graft (CABG) image quality using a 256-slice computed tomography (CT) scanner.

Methods

A total of 78 patients with 254 CABG (762 graft segments) were recruited to undergo CABG assessment with 256-slice CT and prospective ECG-gating. Two observers rated graft segments for image quality on a 5-point scale. Quantitative measurements were also made. Logistic and cumulative link mixed models were used to assess the predictors of graft image quality.

Results

Graft image quality was judged as diagnostic (scores 5 (excellent), 4 (good) and 3 (moderate)) in 96.6% of the 762 segments. Interobserver agreement was excellent (kappa ≥0.90). Graft image quality was not affected by heart rate level. However, high heart rate variability was associated with an important and significant image quality deterioration (odds ratio 4.31; p  =  0.036). Distal graft segments had significantly lower image quality scores than proximal segments (p ≤ 0.02). Significantly higher noise was noted at the origin of the mammary grafts (p  =  0.001), owing to streak artifacts from the shoulders.

Conclusion

CABG imaging with 270-msec rotation 256-slice CT and prospective ECG-gating showed an adequate image quality in 96.6% of graft segments, and an excellent interobserver agreement. Graft image quality was not influenced by heart rate level. Image quality scores were however significantly decreased in patients with high heart rate variability, as well as in distal graft segments, which are closer to the heart.

Computed tomography angiography of coronary artery bypass grafts: robustness in emergency and clinical routine settings

BACKGROUND

There is a high probability for presence of irregular heart rates and artifacts in patients with previous coronary artery bypass graft (CABG) surgery. Previously reported diagnostic performance of ECG-gated 64-slice dual-source computer tomography angiography (CTA) in this patient group is based on pre-selection for normal heart rate and routine clinical setting.

PURPOSE

To investigate image quality and diagnostic performance of CTA in patients with previous CABG surgery in various clinical settings.

MATERIAL AND METHODS

Fifty-six non-selected, consecutive patients (110 grafts, 44 arterial, 66 venous) with previous CABG surgery were prospectively examined using a dual-source 64-slice CT (Siemens Definition, Forchheim, Germany) without utilization of CT-related pharmaceutical heart rate control. Patients were stratified according to the clinical setting: planned redo-cardiac surgery; emergency CTA within 30 days after CABG surgery; routine follow-up after CABG surgery. A reference standard was available for 30 patients (53.6%; 67/110 grafts). Image quality, artifacts, and graft patency were independently assessed by two observers.

RESULTS

All CTAs were diagnostic despite the presence of irregular heart rhythm (25% of cases) and artifacts (72.7% of grafts). CTA was accurate in all patient groups in assessing graft patency (97.9% sensitivity; 100% specificity; 98.5% accuracy) but artifacts decreased diagnostic performance for stenosis detection (60% sensitivity; 88.6% specificity; 84.1% accuracy). Arterial grafts exhibited more surgical clip artifacts compared to venous grafts, which predominantly showed motion artifacts. Overall diagnostic quality was rated excellent in 70.9%/56.4%, good in 23.4%/39.1%, and sufficient in 5.5%/4.5% by each observer, respectively. CTA detected acute findings in 10 cases (graft bleeding, graft occlusion, pericardial hematoma, sternal instability with retrosternal abscess formation, pericardial effusion, left ventricle thrombus) in the emergency group; seven cases required surgical revision.

CONCLUSION

Dual-source CTA is a robust and accurate method for assessment of graft patency and detection of relevant extra-cardiac pathologies in a non-selected patient population after CABG surgery in routine as well as emergency clinical settings. Artifacts caused by irregular heart rhythm or surgical clips do not impair graft patency evaluation but limit stenosis assessment.

Imaging of cardiac valves by computed tomography

This paper describes "how to" examine cardiac valves with computed tomography, the normal, diseased valves, and prosthetic valves. A review of current scientific literature is provided. Firstly, technical basics, "how to" perform and optimize a multislice CT scan and "how to" interpret valves on CT images are outlined. Then, diagnostic imaging of the entire spectrum of specific valvular disease by CT, including prosthetic heart valves, is highlighted. The last part gives a guide "how to" use CT for planning of transcatheter aortic valve implantation (TAVI), an emerging effective treatment option for patients with severe aortic stenosis. A special focus is placed on clinical applications of cardiac CT in the context of valvular disease.

Imaging of coronary artery bypass grafts by computed tomography coronary angiography

In recent years, computed tomography coronary angiography is commonly performed as a follow-up examination after coronary artery bypass graft surgery. Coronary grafts owing to their minimal motion are well visualized by computed tomography coronary angiography, allowing radiologists to assess their patency noninvasively with very high diagnostic accuracy. The purpose of this pictorial essay is to provide an excellent overview of the anatomy and findings concerning coronary artery bypass grafts.

Postmortem imaging of sudden cardiac death

Postmortem imaging is increasingly used in forensic practice in cases of natural deaths related to cardiovascular diseases, which represent the most common causes of death in developed countries. While radiological examination is generally considered to be a good complement for conventional autopsy, it was thought to have limited application in cardiovascular pathology. At present, multidetector computed tomography (MDCT), CT angiography, and cardiac magnetic resonance imaging (MRI) are used in postmortem radiological investigation of cardiovascular pathologies. This review presents the actual state of postmortem imaging for cardiovascular pathologies in cases of sudden cardiac death (SCD), taking into consideration both the advantages and limitations. The radiological evaluation of ischemic heart disease (IHD), the most frequent cause of SCD in the general population of industrialized countries, includes the examination of the coronary arteries and myocardium. Postmortem CT angiography (PMCTA) is very useful for the detection of stenoses and occlusions of coronary arteries but less so for the identification of ischemic myocardium. MRI is the method of choice for the radiological investigation of the myocardium in clinical practice, but its accessibility and application are still limited in postmortem practice. There are very few reports implicating postmortem radiology in the investigation of other causes of SCD, such as cardiomyopathies, coronary artery abnormalities, and valvular pathologies. Cardiomyopathies representing the most frequent cause of SCD in young athletes cannot be diagnosed by echocardiography, the most widely available technique in clinical practice for the functional evaluation of the heart and the detection of cardiomyopathies. PMCTA and MRI have the potential to detect advanced stages of diseases when morphological substrate is present, but these methods have yet to be sufficiently validated for postmortem cases. Genetically determined channelopathies cannot be detected radiologically. This review underlines the need to establish the role of postmortem radiology in the diagnosis of SCD.

Diagnostic accuracy of 64-slice multidetector computed tomography in evaluation of post-coronary artery bypass grafts in correlation with invasive coronary angiography

64-slice multidetector computed tomography (MDCT) allows more reliable and non-invasive evaluation of the coronary artery bypass grafts for occlusion or stenosis both in symptomatic and asymptomatic patients and also progression of disease in native coronary vessels.

Reappraisal of a 20-year experience with the radial artery as a conduit for coronary bypass grafting

OBJECTIVE

This study aimed at evaluating the clinical and angiographic results of the radial artery (RA) used as a coronary bypass graft over 20 years.

METHODS

Clinical follow-up was obtained in 563 patients at 9.2 years. Angiographic follow-up was obtained in 351 patients with opacification of 1427 conduits, including 629 RA at 7.0 years.

RESULTS

At 9.2 years, freedom from overall and cardiovascular death was 80.3% and 92.7%, respectively. Symptoms were: acute myocardial infarction: 2.1% (n=12); angina: 17.4% (n=98), and congestive heart failure 10.6% (n=60). Percutaneous revascularization was required in 13.5% (n=76) of cases on: native coronary (n=77), RA conduit (n=21), and other graft (n=7). Reoperation was needed in 2.3% (n=13) of cases for valve replacement (n=10) and redo coronary artery bypass grafting (CABG) (n=3). At 7.0 years, RA patency was 82.8% (521/629) and was lower than that of left internal mammary artery (IMA), 95.5% (491/514) (p<0.001); similar to right IMA, 87.9% (51/58, p=0.32); free IMA, 80.0% (44/55, p=0.60); and vein, 81.9% (140/171, p=0.77). RA patency was lower in the case of myocardial ischemia: 74.0% (174/235) versus 88.1% (347/394) in asymptomatics (p<0.001). RA patency was higher for diagonal (93.1% (95/102)) compared to circumflex (82.5% (274/332, p<0.01)) and right coronary (77.6% (146/188, p<0.001)). Calcium channel blockers had no impact on RA patency. Separating four groups at successive follow-up intervals, RA patency was: 86.2%, 81.9%, 81.4%, and 81.6% at 1.0, 5.4, 8.3, and 13.1 years, respectively.

CONCLUSION

CABG with the RA offered long-lasting clinical benefit. Beyond the first postoperative year during which some attrition was observed, RA patency was remarkably stable for up to 20 years.

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.

Noninvasive evaluation of coronary artery bypass grafts with 16-slice multidetector computed tomography

BACKGROUND

The aim of this study was to investigate the diagnostic accuracy of 16-slice multislice, multidetector computed tomography (MDCT) angiography for the evaluation of grafts in patients with coronary artery bypass grafting (CABG).

METHODS

Fifty-eight consecutive patients with CABG who underwent both MDCT and conventional invasive coronary angiography were included. The median time interval between the 2 procedures was 10 days (range, 1-32 days). The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of MDCT for the detection of occluded grafts were calculated. The accuracy of MDCT angiography for detecting significant stenoses in patent grafts and the evaluability of proximal and distal anastomoses were also investigated.

RESULTS

Optimal diagnostic images could not be obtained for only 3 (2%) of 153 grafts. Evaluation of the remaining 150 grafts revealed values for sensitivity, specificity, PPV, NPV, and diagnostic accuracy of the MDCT angiography procedure for the diagnosis of occluded grafts of 87%, 97%, 94%, 93%, and 92%, respectively. All of the proximal anastomoses were optimally visualized. In 4 (8%) of 50 patent arterial grafts, however, the distal anastomotic region could not be evaluated because of motion and surgical-clip artifacts. The accuracy of MDCT angiography for the detection of significant stenotic lesions was relatively low (the sensitivity, specificity, PPV, and NPV were 67%, 98%, 50%, and 99%, respectively). The number of significant lesions was insufficient to reach a reliable conclusion, however.

CONCLUSION

Our study showed that MDCT angiography with 16-slice systems has acceptable diagnostic performance for the evaluation of coronary artery bypass graft patency.

Evaluation of ITA Graft Function Using CT Angiography

OBJECTIVE

A less invasive method to assess internal thoracic artery (ITA) graft function after coronary artery bypass grafting (CABG) is desired. This study reports the novel method to estimate ITA graft function using CT angiography.

MATERIALS AND METHODS

Fifty ITA grafts were assessed. Hounsfield Unit transition of each graft on the same cross section was detected during the Test Bolus Injection, which led to the making of a time density curve (TDC), for each ITA. Variables from the TDC were compared statistically with data obtained from Pulse Doppler Echo (PDE), the best indicator of graft function, of ITA grafts.

RESULTS

The ascending slope of the TDC was significantly associated with the following PDE data: Velocity time integral (VTI), VTI × Heart Rate (HR) and Mean Flow of ITA graft. A multivariate analysis showed an especially strong relationship with the ascending slope of the TDC and VTI × HR (R(2) = 0.588).

CONCLUSION

The ascending slope of the TDC means the concentration transition of contrast media, which may be affected by the blood stream in the ITA graft. This study suggests the possibility of the ability to assess ITA graft function by CT angiography.

Integrative computed tomographic imaging of cardiac structure, function, perfusion, and viability

Recent advances in multidetector-row computed tomography (MDCT) technology have created new opportunities in cardiac imaging and provided new insights into a variety of disease states. Use of 64-slice coronary computed tomography angiography has been validated for the evaluation of clinically relevant coronary artery stenosis with high negative predictive values for ruling out significant obstructive disease. This technology has also advanced the care of patients with acute chest pain by simultaneous assessment of acute coronary syndrome, pulmonary embolism, and acute aortic syndrome ("triple rule out"). Although MDCT has been instrumental in the advancement of cardiac imaging, there are still limitations in patients with high or irregular heart rates. Newer MDCT scanner generations hold promise to improve some of these limitations for noninvasive cardiac imaging. The evaluation of coronary artery stenosis remains the primary clinical indication for cardiac computed tomography angiography. However, the use of MDCT for simultaneous assessment of coronary artery stenosis, atherosclerotic plaque formation, ventricular function, myocardial perfusion, and viability with a single modality is under intense investigation. Recent technical developments hold promise for accomplishing this goal and establishing MDCT as a comprehensive stand-alone test for integrative imaging of coronary heart disease.

The detection of pulmonary embolisms after a coronary artery bypass graft surgery by the use of 64-slice multidetector CT

The purpose of this study was to examine the incidence of pulmonary embolism (PE) after a coronary artery bypass graft (CABG) using 64-slice multidetector CT (MDCT), and to determine the correlations between the occurrence of a PE and the clinical or surgical parameters. Three hundred and twenty-six consecutive patients, who underwent coronary CT angiography using 64-slice MDCT to assess the graft patency after CABG, were enrolled in this study. Additional axial CT images, which were reconstructed by adopting a large field of view and thinner image slices, were reviewed for the presence of PE. The relationship between the occurrence of a PE and the type of surgery (off-pump CABG versus conventional CABG), number of target vessels, use of a saphenous vein graft, and length of stay in the intensive care unit (ICU) were evaluated. PE was detected on the CT images of 33 patients (10.1%), which involved the lobar or more proximal arteries in seven patients and the segmental or subsegmental arteries in 26. PE occurred more frequently after off-pump CABG (16.5%, 14/85) than after conventional CABG (7.9%, 19/241) (P = 0.024). Patients with PE were older (67 years vs. 62.7 years) and had longer stays in the ICU (5.6 days vs. 3.8 days) than those without (P = 0.013 and P = 0.007, respectively). No significant difference was observed in the number of target vessels and use of a saphenous vein graft between patients with and without an embolism. In a multi-variable analysis, the age of the patient, surgical methods, and ICU stay were independent predictors for the occurrence of PE (P = 0.013, P = 0.017, and P = 0.005, respectively). MDCT helps detect PE in patients after CABG. It is encountered more frequently after off-pump CABG than after conventional CABG and in older patients with longer ICU stays.

Late improvement in graft patency after coronary artery bypass grafting: Serial assessment with multidetector computed tomography in the early and late postoperative settings

OBJECTIVE

Grafts initially showing poor patency after coronary artery bypass grafting have occasionally shown improvement on serial multidetector computed tomography. This study analyzed possible factors associated with this phenomenon.

METHODS

Between September 2003 and July 2007, 512 patients underwent multidetector computed tomography within 1 month of isolated coronary artery bypass grafting. Among them, 1720 distal anastomoses were made with 1042 arterial and 302 venous conduits. Of these, 95 grafts (in 73 patients) were faint (n = 67) or nonvisualized (n = 28). Seventy-three of these grafts (in 56 patients) had follow-up multidetector computed tomographic evaluation 1 year after surgery and comprised the study group.

RESULTS

Improvement in graft patency (faint to patent or nonvisualization to visualization) occurred in 44 grafts (60.3%). Multivariate analysis revealed proximal target vessel stenosis of at least 90% (relative risk, 3.81; P = .009), larger target coronary size (relative risk, 1.72; P = .002), and radial artery graft use (relative risk, 4.44; P = .003) to be significantly associated with the graft patency restoration. Graft patency restoration was most commonly observed in a group of 28 radial artery grafts that were anastomosed to target vessel with proximal stenosis of at least 90%; of these grafts, 24 (85.7%) showed improved graft patency on follow-up.

CONCLUSIONS

A large proportion of radial artery grafts initially showing poor opacification after coronary artery bypass grafting demonstrated patency restoration on serial multidetector computed tomography. Larger target vessel size and target vessel stenosis of at least 90% were significant correlative factors.

Coming of age: coronary computed tomography angiography

Technical development has substantially improved diagnostic performance of coronary computed tomography angiography (CCTA). A large number of studies have addressed proof of concept, feasibility, and clinical robustness of this noninvasive diagnostic technique, and most have consistently described the ability of CCTA to reliably rule out significant coronary artery stenosis. Clinical evidence supports the significant role of CCTA in an increasing number of scenarios, including the detection of coronary disease in symptomatic patients who are at intermediate risk and evaluation of coronary revascularization procedures. After initial feasibility testing, the scientific evaluation of CCTA now points toward analyzing prognosis, outcome, and cost-effectiveness of this noninvasive diagnostic tool. In this article, appropriate clinical indications, diagnostic performance, current clinical applications, prognostic value, and cost-effectiveness of CCTA are reviewed.

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.

Low dose high-pitch spiral acquisition 128-slice dual-source computed tomography for the evaluation of coronary artery bypass graft patency

OBJECTIVES

To prospectively assess electrocardiography (ECG)-synchronized dual-source computed tomography (CT) in high-pitch spiral acquisition mode for the evaluation of coronary artery bypass graft (CABG) patency regarding image quality and radiation dose.

MATERIALS AND METHODS

Fifty consecutive patients (47 men, age 69.6 +/- 9.6 years, body mass index 26.6 +/- 3.5 kg/m) underwent clinically indicated 128-slice dual-source CT angiography of the entire thorax for the evaluation of graft patency after CABG surgery using a prospectively ECG-synchronized high-pitch spiral acquisition mode (pitch 3.2; 100 kV tube voltage, 0.28 seconds gantry rotation time). Heart rates (HR) were noted. Image quality of the proximal anastomosis, graft body, distal anastomosis, and postanastomotic coronary artery were graded by 2 independent readers on a 3-point scale (1 = excellent, 2 = moderate, and 3 = poor/nondiagnostic). Quantitative image quality parameters (noise, contrast-to-noise ratio) were measured. Effective radiation doses were calculated.

RESULTS

Mean HR was 76 +/- 19 bpm (range, 45-135 bpm). Median scan time was 0.9 seconds (range, 0.76-1.17 seconds), mean scan length was 349 +/- 38 mm (range, 294-452 mm). A total of 125 CABG (54% arterial grafts) and 465 vessel sections were analyzed. Twelve grafts were proximally occluded. Diagnostic image quality was obtained in 462 (99.4%) sections. Of those, image quality was excellent in 397 (85.4%) and moderate in 65 (14.0%). All 3 (0.6%) nondiagnostic sections affected the distal anastomosis due to motion artifacts caused by high HR. Separating the study population by the median HR of 71 bpm, image quality of the distal anastomosis regarding motion artifacts was significantly lower at high HR (P < 0.05). Interobserver agreement in grading image quality of graft segments was good (kappa = 0.77). Image noise in the aorta was 36.9 +/- 8.1, contrast-to-noise ratio was 13.1 +/- 4.2. Effective radiation dose was 2.3 +/- 0.3 mSv.

CONCLUSIONS

The patency of coronary artery bypass grafts can be assessed with decreasing image quality at high HR in high-pitch prospectively ECG-synchronized thoracic 128-slice dual-source CT angiography at a low radiation dose.

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.

Non-invasive assessment of coronary artery bypass grafts and native coronary arteries using 64-slice computed tomography: comparison with invasive coronary angiography

INTRODUCTION AND OBJECTIVES

Although the diagnostic accuracy of CT in the non-invasive assessment of coronary arteries and grafts is known to be high, only a few studies have investigated the technique's reliability for the combined assessment of native coronary arteries, grafts, and vessels lying distal to anastomoses. The aim of this study was to evaluate the diagnostic accuracy of 64-slice CT for assessing coronary grafts and native coronary arteries.

METHODS

In the study, 64-slice CT was used to evaluate 36 patients who had undergone coronary artery bypass graft surgery and had a clinical indication for angiographic graft assessment. The diagnostic accuracy of CT for identifying significant lesions in grafts and native coronary arteries was determined and compared with that of invasive coronary angiography.

RESULTS

Of the 103 grafts studied (49 arterial and 54 venous), 96 (93.2%) could be visualized by angiography and 98 (95.1%) by CT. The sensitivity and specificity of CT for detecting significant lesions in grafts were 100% (30/30) and 97% (64/66), respectively, and the positive predictive value (PPV) and negative predictive value (NPV) were 94% and 100%, respectively. For non-revascularized coronary arteries (258 segments), the sensitivity, specificity, PPV and NPV were 94%, 95%, 80%, and 99%, respectively, and for distal vessels, 86%, 97%, 67%, and 99%, respectively.

CONCLUSIONS

The diagnostic accuracy of 64-slice CT for evaluating both coronary grafts and native coronary arteries was high.

Clinical impact of computerised tomographic angiography performed for preoperative evaluation before coronary artery bypass grafting

OBJECTIVE

In our institution, computerised tomographic (CT) angiography has been performed as a near-routine test before coronary artery bypass grafting (CABG) to evaluate the aorta and its branches. We aimed to determine its impact on operative procedure and perioperative management.

METHODS

From January 2006 through December 2008, neck-to-leg systemic arteries were evaluated by 64-slice multidetector CT scan in 284 patients before CABG. For them, medical records and cardiac surgery database were retrospectively reviewed to investigate the incidence of pathologic lesions of the aorta and its major branches, other incidental lesions and procedure- or management-related decision affected by CT angiography.

RESULTS

In 36 patients (12.7%), cannulation and clamping of the ascending aorta were thought too dangerous because of severe atherosclerotic change. The use of cardiopulmonary bypass was inevitable in 10 of them, and postoperative mortality rate was significantly higher (3/10, 30%) than in the remaining patients (2/274, 0.7%). Conduit selection or grafting strategy was changed due to severe left subclavian artery stenosis or leg vein varicosity in 18 patients (6.3%). For the following problems, surgical interventions were performed in 34 patients (12.0%) concomitantly or during the same admission with CABG; > or = 90% stenosis in carotid (5.6%), iliofemoral (11.6%) or renal (4.6%) arteries, aortic aneurysm (14.4%, six of them met surgical indication) and incidental malignant neoplasm (2.8%). Counting all of the above, preoperative CT angiography affected risk assessment, CABG procedure itself, perioperative management or follow-up plan in 142 patients (50%).

CONCLUSIONS

Because preoperative CT angiography considerably affected management in one half of patients, we recommend its use as a routine test before CABG, unless contraindicated.

X-ray computed tomography of the heart

INTRODUCTION

Cardiac imaging is an emerging application of multidetector computed tomography (MDCT). This review summarizes the current capabilities, possible applications, limitations and developments of cardiac CT.

SOURCES OF DATA

Relevant publications in peer reviewed literature and national and international guidelines are used to discuss important issues in cardiac CT imaging.

AREAS OF AGREEMENT AND CONTROVERSY

There is broad consensus that coronary CT angiography is indicated in patients with an intermediate pre-test probability of coronary artery disease (CAD) when other non-invasive tests have been equivocal. In this context, CT can reliably exclude significant CAD. Cardiac CT also has an established role in the evaluation of bypass grafts and suspected coronary anomalies. Radiation exposure from CT procedures remains a concern, although techniques are now available to reduce the X-ray dosage without significantly compromising the image quality. However, with the current level of knowledge, the cardiac CT examinations are not justified to screen for CAD in asymptomatic individuals. Neither is it considered appropriate in patients with a high pre-test probability of CAD, for whom invasive catheter coronary angiography is usually of more benefit.

GROWING POINTS AND AREAS TIMELY FOR DEVELOPING RESEARCH

The ability to reconstruct the volumetric cardiac CT data set opens up avenues for advanced physiological analyses of the heart. For example, if CT myocardial perfusion assessment becomes a reality, there is potential to revolutionize the practice of MDCT imaging. Research is also ongoing to investigate whether cardiac CT has a role in the appropriate triage of patients with chest pain in the emergency department.

Achados de imagem da revascularização do miocárdio pela tomografia computadorizada por múltiplos detectores: onde estão os enxertos? Ensaio iconográfico

A angiotomografia por multidetectores de coronárias constitui um método preciso para avaliação dos enxertos venosos e arteriais pós-revascularização coronariana e vem substituindo em parte o cateterismo, o qual é um método invasivo e de maior custo. Este ensaio iconográfico tem como objetivo a demonstração anatômica dos enxertos mais comumente utilizados, como diferenciar enxertos venosos e arteriais e como localizá-los. Os exames foram realizados em aparelhos de tomografia computadorizada multislice de 64 fileiras de detectores, com apneia, frequência cardíaca controlada e protocolos adequados com posterior reconstruções MPR, MIP e 3D, de acordo com o eletrocardiograma. A localização dos enxertos e anastomoses em tomografias computadorizadas direcionadas para as artérias coronárias e para o tórax pode dificultar a análise do exame pelo radiologista não familiarizado, sendo que o conhecimento das técnicas cirúrgicas utilizadas e dos possíveis trajetos das pontes de safena e enxertos arteriais ajuda na análise de ambos os exames, evitando também erros diagnósticos.

Transitioning from 16-slice to 64-slice multidetector computed tomography for the assessment of coronary artery disease: are we really making progress?

BACKGROUND

Multidetector computed tomography (MDCT) has demonstrated promise in the noninvasive evaluation of coronary artery disease.

OBJECTIVE

To systematically review the literature regarding the improved diagnostic accuracy of 64-slice MDCT.

METHODS

An EMBASE, OVID, PubMed and Cochrane Library database search was performed using the key words 'computed tomography' matched with the terms 'coronary artery' or 'coronary angiography' to identify English-language articles examining MDCT cardiac imaging. Studies that compared 16-slice or 64-slice MDCT with catheter-based coronary angiography for the detection of coronary artery disease in nonrevascularized, poststent and post-coronary artery bypass graft patients were included. Data were pooled to obtain a weighted sensitivity, specificity and diagnostic accuracy for MDCT. Negative and positive predictive values, and likelihood ratios were calculated based on sensitivity and specificity.

RESULTS

Currently, 15 studies involving 1008 patients have examined the efficacy of 64-slice MDCT in the assessment of coronary artery stenosis (more than 50% luminal narrowing). In these studies, 64-slice MDCT has demonstrated a sensitivity (89%), specificity (96%) and diagnostic accuracy (95%) similar to that of 16-slice MDCT. However, 64-slice MDCT was able to assess 5% more coronary artery segments than 16-slice MDCT. In revascularized patients, MDCT can accurately assess both bypass graft occlusion and stenosis. The 64-slice MDCT is also capable of adequately detecting in-stent restenosis. Improvements in spatial and temporal resolution with 64-slice technology have decreased the occurrence of high attenuation and motion artefacts that plagued the previous generation of MDCT scanners.

CONCLUSION

MDCT offers an accurate assessment of the coronary arteries, stented arteries and bypass grafts. The improved accuracy and safety of MDCT may reduce the need for catheter-based coronary angiography.

Angina associated with left main coronary artery compression in pulmonary hypertension

Chest pain is a common complaint in patients with pulmonary arterial hypertension (PAH). Left main coronary artery (LMCA) compression by an enlarged pulmonary artery trunk (PAT) has been associated with angina, but appropriate diagnostic and treatment approaches remain poorly defined. We present two cases of angina caused by LMCA compression from an enlarged pulmonary artery, one of which also presented with new, severe left ventricular systolic dysfunction attributed to myocardial ischemia. Diagnosis of LMCA stenosis was made via coronary angiography followed by computed tomography-gated coronary angiography (CT-CA), which confirmed pulmonary artery enlargement as the source of extrinsic compression. Restoring LMCA patency with percutaneous intervention and/or aggressive treatment of pulmonary hypertension led to significant improvement in angina, cardiac function and quality of life. Given the negative impact on cardiac function, prompt diagnosis and treatment of extrinsic LMCA compression should be considered a priority.

Cardiac CT angiography after coronary artery surgery in children using 64-slice CT scan

OBJECTIVE

The purpose of this study was to compare the diagnostic accuracy of 64-slice CT with that of invasive angiography in the detection of graft and/or coronary angioplasty stenosis in children who had undergone coronary artery surgery.

POPULATION AND METHODS

Fifteen consecutive children (8 male and 7 female; age 9.2+/-6.1 years) underwent 64-slice CT because of chest pain or ECG changes mean 4.8+/-3.7 years after surgical coronary artery surgery; 10 patients had coronary angioplasty using a patch from the saphenous vein, four had mammary artery bypass, and one had saphenous vein bypass. Six main segments of the coronary arteries and all the bypass graft considered as a single segment were analyzed and compared with invasive angiography used as the reference standard.

RESULTS

CT correctly identified the four children with coronary angioplasty and mammary graft lesions that were confirmed by conventional angiography: one patient had a significant stenosis (>50% stenosis) at the mammary bypass graft anastomosis site; three other had non-significant stenosis (<50% stenosis) including a mild lesion of the saphenous vein patch in two patients and a mild lesion at the anastomosis site of the mammary bypass in one. All segments identified as normal by CT in the other 11 children were also found to be normal by conventional angiography.

CONCLUSION

In centers expert in this technique, 64-slice CT scanning is a promising, rapid, and useful diagnostic technique for evaluating both coronary angioplasty and bypass graft lesions in children who had undergone coronary artery surgery.