Coronary Artery Bypass Grafts: Assessment with Multidetector CT in the Early and Late Postoperative Settings

Non-contrast computed tomography findings for identification of chronically occluded coronary artery bypass grafts

BACKGROUND

Detecting occlusions of coronary artery bypass grafts using non-contrast computed tomography (CT) series is understudied and underestimated.

PURPOSE

To evaluate morphological findings for the diagnosis of chronic coronary artery bypass graft occlusion on non-contrast CT and investigate performance statistics for potential use cases.

MATERIAL AND METHODS

Seventy-three patients with coronary artery bypass grafts who had CT angiography of the chest (non-contrast and arterial phases) were retrospectively included. Two readers applied pre-set morphologic findings to assess the patency of a bypass graft on non-contrast series. These findings included vessel shape (linear-band like), collapsed lumen and surgical graft marker without a visible vessel. Performance was tested using the simultaneously acquired arterial phase series as the ground truth.

RESULTS

The per-patient diagnostic accuracy for occlusion was 0.890 (95% confidence interval = 0.795-0.951). Venous grafts overall had an 88% accuracy. None of the left internal mammary artery to left anterior descending artery arterial graft occlusions were detected. The negative likelihood ratio for an occluded graft that is truly patent was 0.121, demonstrating a true post-test probability of 97% for identifying a patent graft as truly patent given a prevalence of 20% occlusion at a median 8.4 years post-surgery. Neither years post-surgery, nor number of vessels was associated with a significant decrease in reader accuracy.

CONCLUSION

Evaluation of coronary bypass grafts for chronic occlusion on non-contrast CT based off vessel morphology is feasible and accurate for venous grafts. Potential use cases include low-intermediate risk patients with chest pain or shortness of breath for whom non-contrast CT was ordered, or administration of iodine-based contrast is contraindicated.

RADIATION DOSE REDUCTION AT LOW TUBE VOLTAGE WITH CORONARY ARTERY BYPASS GRAFT COMPUTED TOMOGRAPHY ANGIOGRAPHY BASED ON THE CONTRAST NOISE RATIO INDEX

To compare the radiation dose and diagnostic ability of the 100-kVp protocol, based on the contrast noise ratio (CNR) index, during coronary artery bypass graft (CABG) vessels with those of the 120-kVp protocol. For the 120-kVp scans (150 patients), the targeted image level was set at 25 Hounsfield units (HU) (CNR120 = iodine contrast/25 HU). For the 100-kVp scans (150 patients), the targeted noise level was set at 30 HU to obtain the same CNR as in the 120-kVp scans (i.e. using 1.2-fold higher iodine contrast, CNR100 = 1.2 × iodine contrast/(1.2 × 25 HU) = CNR120). We compared the CNRs, radiation doses, detection of CABG vessels and visualisation scores of the scans acquired at 120 and 100 kVp, respectively. At the same CNR, the 100-kVp protocol may help reduce the radiation dose by ⁓30% compared with the 120-kVp protocol, without degradation of diagnostic ability during CABG.

Role of MDCT in Assessment of Long-term Graft Patency in Female Patients

Objectives:

The aim of the study was to analyze the utility of CT-coronary angiogram (CT-CAG) in assessment of long-term graft patency compared to conventional invasive coronary angiography (ICA) and highlight any gender-specific issues in female post-coronary artery bypass surgery (CABG) patients.

Materials and Methods:

The medical records and images of 30 patients including four female patients who had CABG in the past and underwent both conventional and CT-CAGs were analyzed retrospectively.

Results:

We studied 30 patients who had CABG in whom both CT-CAG and conventional coronary angiograms were performed. CT-CAG was able to evaluate the grafts better than ICA and was useful even in those which could not be assessed due to technical failure by ICA. There were only four female patients in this series. In first patient, the arterial graft (left internal mammary artery [LIMA]) was patent but distal run off was absent in LAD in CT-CAG images and was reported as poor in conventional coronary angiogram. The second patient had CABG 10 years back. The arterial graft (LIMA) to LAD was patent and there was total block in SVG graft to RCA at proximal anastomotic site. The third patient with hypertension and diabetes also had CABG 10 years back. Both LIMA to LAD and SVG to PDA were patent in her. In last case who had CABG 7 years, two of the three SVG grafts were blocked which were well-demonstrated on CT CAG, including one SVG missed on conventional CAG.

Conclusion:

CT-CAG is a non-invasive and less cumbersome alternative to conventional CAG for the assessment of grafts long after CABG even in women. The data generated by CT-CAG in post-CABG are as good as the invasive CAG and it has distinct advantage of greater acceptability.

Routine early postoperative computed tomography angiography after coronary artery bypass surgery: clinical value and management implications

OBJECTIVES

Computed tomography angiography (CTA) is broadly used for long-term follow-up of graft patency after coronary artery bypass graft surgery (CABG). However, its clinical value in the early postoperative setting has not been established yet. We evaluated the benefit of adding CTA to the routine clinical work-up after CABG on patient management.

METHODS

A total of 305 consecutive patients (269 males, median age 68 years) underwent CABG and postoperative CTA with a median of 6 days after surgery. Graft patency and additional imaging findings were assessed and their influence on diagnosis and clinical management was evaluated.

RESULTS

Graft occlusion or high-grade stenosis was found in 15% of the patients. Additional findings were reported in 44% of the patients, including pericardial (2%) and pleural effusion (27%), large pneumothorax (11%), pulmonary infection (4%), cardiac or vascular thrombus (2%), pulmonary embolism (2%), sternal dehiscence (1%) and additional incidental findings requiring follow-up (6%). CT findings initiated new diagnostic and/or therapeutic measures in 15% of the patients, 47% of those with diseased grafts and 19% of patients with non-graft-related findings. No adverse events related to CTA were documented.

CONCLUSIONS

Early routine postoperative assessment of CABG with CTA reveals both cardiac and non-cardiac findings with a high frequency, affecting clinical management in a substantial proportion of patients.

Resilience of the Internal Mammary Artery to Atherogenesis: Shifting From Risk to Resistance to Address Unmet Needs

Fueled by the global surge in aging, atherosclerotic cardiovascular disease reached pandemic dimensions putting affected individuals at enhanced risk of myocardial infarction, stroke, and premature death. Atherosclerosis is a systemic disease driven by a wide spectrum of factors, including cholesterol, pressure, and disturbed flow. Although all arterial beds encounter a similar atherogenic milieu, the development of atheromatous lesions occurs discontinuously across the vascular system. Indeed, the internal mammary artery possesses unique biological properties that confer protection to intimal growth and atherosclerotic plaque formation, thus making it a conduit of choice for coronary artery bypass grafting. Its endothelium abundantly expresses nitric oxide synthase and shows accentuated nitric oxide release, while its vascular smooth muscle cells exhibit reduced tissue factor expression, high tPA (tissue-type plasminogen activator) production and blunted migration and proliferation, which may collectively mitigate intimal thickening and ultimately the evolution of atheromatous plaques. We aim here to provide insights into the anatomy, physiology, cellular, and molecular aspects of the internal mammary artery thereby elucidating its remarkable resistance to atherogenesis. We propose a change in perspective from risk to resilience to decipher mechanisms of atheroresistance and eventually identification of novel therapeutic targets presently not addressed by currently available remedies.

Incidental Finding and Endovascular Repair of a Left Internal Mammary Artery Aneurysm following a Multivessel Coronary Artery Bypass Graft

True aneurysms discovered within the internal mammary artery are extremely rare and typically have an asymptomatic occurrence. Their presentation and management have also been variable due to their low incidence, decreased detection, or lack of documentation. They have a high risk for morbidity or mortality as they can possibly rupture with increasing size and thus become life-threatening. Coronary CT angiography is the most definitive test for confirming and finding complications related to the aneurysm. With an increase in the aging population and advancement in the techniques used in coronary artery bypass grafting, it is likely that the rate of recorded occurrence of aneurysms and pseudoaneurysms will increase. Endovascular repair is currently the most favored treatment modality. In this report, we describe a case of a 74-year-old male who was incidentally found to have a left internal mammary artery aneurysm following complaints of chest pain related to another nearly occluded grafted vessel. To the best of our knowledge, and following an extensive literature review, this is likely the first documented case of a true aneurysm found within a left internal mammary artery bypass graft. The patient recovered well following placement of a covered stent; however, upon follow-up one year later, he was found to have stenosis of the same vessel, which was subsequently treated without further complication.

Dynamic kinking of right coronary artery after the button Bentall procedure

Postoperative coronary artery complications after Bentall procedures are well recognised but are rare and potentially fatal. There have been only five cases documenting percutaneous coronary intervention (PCI) for right coronary artery (RCA) involvements after button Bentall procedures. We describe a case of postoperative silent myocardial ischaemia in a 72-year-old man who underwent the button Bentall procedure for a right sinus of Valsalva aneurysm. On postoperative day 15, an RCA complication was incidentally detected by follow-up multidetector CT. Coronary angiography showed proximal RCA kinking, which was not an anastomosis but a native coronary artery. The patient underwent a successful PCI with drug-eluting stent implantation. We reviewed six cases consisting of this case and five previous cases treated with PCI. These cases enhance the recognition of potential RCA complications after the button Bentall procedure.

Thrombosed aneurysm of saphenous vein coronary artery bypass grafting

We describe the case of a male patient, aged 76 years, referred for cardiac investigation due to retrosternal chest pain and dyspnea. He had a history of acute myocardial infarction and angioplasties in the last 30 years, including a saphenous vein coronary artery bypass grafting (SVCABG). Echocardiogram showed hypoechoic oval formation near the right ventricle, suggesting a pericardial cyst. Computed angiotomography revealed a predominantly fusiform and thrombosed aneurysmal dilation of the SVCABG to the right coronary artery. SVCABG aneurysms are very rare and potentially fatal. They usually appear in the late postoperative period, and patients are often asymptomatic. On radiography, it is frequently presented as enlargement of the mediastinum, with echocardiography, computed tomography and magnetic resonance imaging being very useful for diagnosis. Coronary angiography is the gold standard to detect these cases. Our report illustrates a rare situation arising late from a relatively common surgery. Due to its severity, proper recognition in the routine assessment of patients with a similar history is essential.

Coronary artery bypass graft pseudoaneurysm from saphenous vein graft stent fracture

Saphenous venous graft (SVG) pseudoaneurysms are a rare complication of coronary artery bypass grafting (CABG). An 85-year-old man with CABG and a distal SVG stent presented with dyspnea. Chest computed tomography (CT) revealed a large partially thrombosed pseudoaneurysm at the distal SVG with stent fracture. Endoluminal exclusion of the distal SVG pseudoaneurysm using a covered stent was performed. Follow-up chest CT and angiography showed persistent pseudoaneurysm filling and enlargement. The SVG proximal to the pseudoaneurysm was embolized with coils to reduce rupture risk. Following embolization, the patient's left ventricular ejection fraction was moderately depressed but the patient remained stable and was discharged. <Learning objective: Saphenous venous graft pseudoaneurysms are a rare post-operative complication of coronary artery bypass graft procedures with a risk of impending rupture if left untreated. Fracture of a vein graft stent is an even further unique etiology of pseudoaneurysms. Covered stents are a practical therapeutic option for the treatment of vein graft pseudoaneurysms, especially in high risk patients who are not surgical candidates.>.

Cinematic rendering - an alternative to volume rendering for 3D computed tomography imaging

Abstract

Volume rendering (VR) represents today’s standard three-dimensional (3-D) image post-processing technique, and often is used to visualize complex anatomical information. Recently, a novel 3-D technique for post-processing of computed tomography (CT) image data has been introduced, which is called cinematic rendering (CR). The objective of this review is to illustrate the image appearance and potential value of CR in comparison with conventional VR in a number of various applications and different anatomical regions. Similar to VR, CR best visualizes high density and high contrast structures such as bones and contrast-enhanced vessels, but at the same time provides a more natural and photo-realistic illumination of the rendered data. Further research will be necessary for determining possible advantages of CR over conventional VR and over two-dimensional (2-D) image post-processing for CT image data.

Teaching Points

• Cinematic rendering is a novel post-processing technique for 3D visualization of CT image data.

• Compared to volume rendering, CR results in a more photo-realistic representation of anatomy.

• Similar to volume rendering, CR provides best image quality of high density structures.

INTIMAL HYPERPLASIA AND WALL SHEAR IN ARTERIAL BYPASS Y-GRAFTING AND CONSEQUENCE GRAFTING: A NUMERICAL STUDY

The progression of intimal hyperplasia is considered to be the main cause of bypass failure and is directly related to the individual blood rheology, local arterial geometry and placement of the junctions, graft diameter and graft surface characteristics as well as the degree of compliance. In this paper we use commercial computational fluid dynamics (CFD) ANSYS to examine under the correct physiological flow conditions the hemodynamic forces of composite bypass with internal mammary artery in Y-grafting and consequence grafting which is known to achieve high patency rate and highly recommended by clinicians. Particular emphasis is given here on the parameters that could initiate the development of intimal hyperplasia within these bypass configurations. The hemodynamic flow patterns between the consequence grafting and the composite Y-grafting are observed here to be different. Moreover, on both end-to-side and side-to-side configurations, the circulating flows are detected in the vicinity of the junction area, while the Dean flow vortexes are only observed on the end-to-side configuration. Likewise, the hemodynamic flow on the end-to-side configuration on the LCX of both 45° and 90° Y-grafting is found to be smoother than that of the junction on the LCA, regardless of the changing of anastomosis angles. The high WSS gradients are observed at the vicinity of the toe and on the bed of the junction, while the low WSS are presented at the distal of the stenosis and at the stagnation point. The clinical relevance of the results are presented and discussed with particular focus on the factors and the flow patterns that trigger the development of intimal hyperplasia.

Incidental Cardiac Findings on Thoracic Imaging

The cardiac structures are well seen on nongated thoracic computed tomography studies in the investigation and follow-up of cardiopulmonary disease. A wide variety of findings can be incidentally picked up on careful evaluation of the pericardium, cardiac chambers, valves, and great vessels. Some of these findings may represent benign variants, whereas others may have more profound clinical importance. Furthermore, the expansion of interventional and surgical practice has led to the development and placement of new cardiac stents, implantable pacemaker devices, and prosthetic valves with which the practicing radiologist should be familiar. We present a collection of common incidental cardiac findings that can be readily identified on thoracic computed tomography studies and briefly discuss their clinical relevance.

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.

The role of multidetector computed tomography coronary angiography in imaging complications post-cardiac surgery

There have been numerous advances in the field of cardiac imaging. The advent of multidetector computed tomography coronary angiography (MDCT-CA) and in particular electrocardiographic (ECG)-gated acquisition has revolutionized the investigation of the complete spectrum of complications of common cardiothoracic surgical procedures. Generic complications, such as mediastinitis, pericardial effusion, sternal osteomyelitis, and mediastinal fibrosis, are discussed with illustrative examples of multiplanar and volume-rendered three-dimensional reconstructions. Graft-related complications of both coronary artery bypass grafts and aortic root grafts are reviewed. The role of MDCT-CA in the investigation of prosthetic valve endocarditis and root abscesses is outlined. We present a complete illustration of the detailed images that are obtained when investigating a full range of graft-related complications from both aortic and coronary surgery using ECG-gated MDCT-CA. MDCT-CA has the potential to become established as the optimal technique with which to image a multitude of complications post-cardiac surgery.

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.

Endoscopic venous harvesting by inexperienced operators compromises venous graft remodeling

BACKGROUND

Endoscopic vein harvesting (EVH) is the standard of care for coronary artery bypass grafting (CABG) in the United States, but recent comparisons with open harvesting suggest that conduit quality and outcomes may be compromised in EVH. To test the hypothesis that problems with EVH may relate to its learning curve and conduit quality, we analyzed the quality and early function of conduits procured by technicians with varying experience in EVH.

METHODS

Experienced (more than 900 cases, n=55 patients) and novice (less than 100 cases, n=30 patients) technicians performed EVH during CABG. Subsequently, optical coherence tomography (OCT) was used to examine the conduits for vascular injury, with segments identified as injured being further examined for gene expression with an array of genes related to tissue injury. Conduit diameter was measured intra- and postoperatively (day 5 and 6 months, respectively) with OCT and computed tomographic angiography.

RESULTS

Endoscopic vein harvesting by novice harvesters resulted in a greater number of discrete graft injuries and greater expression of tissue-injury genes than EVH done by experienced harvesters. Regression analysis revealed an association between shear stress and early dilation of engrafted vessels (positive remodeling) (R2=0.48, p<0.01). Injured veins showed blunted positive remodeling at 5 days after harvesting and a greater degree of late lumen loss at 6 months.

CONCLUSIONS

Under normal conditions, intraluminal shear stress leads to positive remodeling of vein grafts during the first postoperative week. Injury to conduits, a frequent sequela of the learning curve for EVH, was a predictor of early graft failure and of blunted positive remodeling and greater negative remodeling of endoscopically harvested vein grafts. Given the current annual volume of cases in which EVH is used, rigorous monitoring of the learning curve for this procedure represents an important and unrecognized issue in public health.

Impact of the learning curve for endoscopic vein harvest on conduit quality and early graft patency

BACKGROUND

Recent studies have suggested that endoscopic vein harvest (EVH) compromises graft patency. To test whether the learning curve for EVH alters conduit integrity owing to increased trauma compared with an open harvest, we analyzed the quality and early patency of conduits procured by technicians with varying EVH experience.

METHODS

During coronary artery bypass grafting, veins were harvested open (n=10) or by EVH (n=85) performed by experienced (>900 cases, >30/month) versus novice<100 cases, <3/month) technicians. Harvested conduits were imaged intraoperatively using optical coherence tomography and on day 5 to assess graft patency using computed tomographic angiography.

RESULTS

Conduits from experienced (n=55) versus novice (n=30) harvesters had similar lengths (33 versus 34 cm) and harvest times (32.4 versus 31.8 minutes). Conduit injury was noted in both EVH groups with similar distribution among disruption of the adventitia (62%), intimal tears at branch points (23%), and intimal or medial dissections (15%), but the incidence of these injuries was less with experienced harvesters and rare in veins procured with an open technique. Overall, the rate of graft attrition was similar between the two EVH groups (6.45% versus 4.34% of grafts; p=0.552). However, vein grafts with at least 4 intimal or medial dissections showed significantly worse patency (67% versus 96% patency; p=0.05).

CONCLUSIONS

High-resolution imaging confirmed that technicians inexperienced with EVH are more likely to cause intimal and deep vessel injury to the saphenous vein graft, which increases graft failure risk. Endoscopic vein harvest remains the most common technique for conduit harvest, making efforts to better monitor the learning curve an important public health issue.

Tandem aneurysms of an internal mammary-aortocoronary bypass graft

Graft aneurysms following aortocoronary surgery are a rare occurrence in clinical practice. Reported cases have mostly involved saphenous vein grafts. Here we report the rare finding of a tandem aneurysm of an internal mammary artery graft which was incidentally detected 17 years following bypass surgery. (Neth Heart J 2009;17:300-2.).

Cardiac computed tomography in the evaluation of left anterior descending coronary artery with vein patch reconstruction

PURPOSE

This study evaluated the morphological and functional results of surgical reconstruction of the left anterior descending (LAD) coronary artery with an autologous vein patch, associated with left internal mammary artery (LIMA) grafting onto the patch.

MATERIALS AND METHODS

Cardiac computed tomography (CT) images were assessed in terms of functional and morphological parameters. Function was evaluated by assessing patency at 36 months of the reconstructed LAD (based on the attenuation of the native vessel distal to the anastomosis). Morphology was evaluated by studying vein-patch diameters, profiles and margins, shape and structure to categorise the patches into three groups (A, B, C). Within 1 month of CT, all patients underwent functional testing (bicycle ergometry).

RESULTS

CT imaging correctly depicted the LAD graft, revealing it to be fully patent in all cases. On the basis of our morphological classification, 21 patients were classed as group A, two as group B and two as group C. At bicycle ergometry, 23 patients were negative and two were positive. Group C patients had the worst functional results.

CONCLUSIONS

Cardiac CT allowed adequate evaluation of the LAD graft patency and morphology, and in consideration of its noninvasive nature, it may become the imaging tool of choice for evaluating extended LAD reconstruction.

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.

Inadvertent anastomosis of saphenous vein graft to a cardiac vein detected with coronary computed tomographic angiography

A 34-year-old man with a prior history of Hodgkin's disease and coronary artery bypass surgery for radiation-induced left main disease presented with persistent chest pain. Cardiac catheterization showed near simultaneous filling of the venous system during arterial injection and could not precisely delineate the insertion point of the vein graft anastamosis to the diagonal branch, and the patient was referred for coronary computed tomography angiography (CTA). CTA demonstrated that the anastamosis of the graft was with a cardiac vein. This case illustrates the valuable complementary role of both angiographic methodologies in confirming a complex anatomic diagnosis.

Harmonic scalpel versus electrocautery for harvest of radial artery conduits: reduced risk of spasm and intimal injury on optical coherence tomography

OBJECTIVE

Vasospasm is the primary obstacle to widespread adoption of the radial artery as a conduit in coronary artery bypass grafting. We used optical coherence tomography, a catheter-based intravascular imaging modality, to measure the degree of radial artery spasm induced by means of harvest with electrocautery or a harmonic scalpel in patients undergoing coronary artery bypass grafting.

METHODS

Radial arteries were harvested from 44 consecutive patients with a harmonic scalpel (n = 15) or electrocautery (n = 29). Vessels were imaged before harvesting and after removal from the arm, with saphenous vein tracts serving as internal controls. Optical coherence tomographic findings for the degree of harvesting-induced injury were validated against histologic measures.

RESULTS

Optical coherence tomographic measures of endovascular dimensions and injury correlated strongly with histologic findings. Mean luminal volume, a measure of vasospasm, decreased significantly less after harvesting with a harmonic scalpel (9% +/- 7%) than with electrocautery (35% +/- 6%, P = .015). Completely intact intima was present in 11 (73%) of 15 radial arteries harvested with a harmonic scalpel (73%) compared with 9 of 29 arteries harvested by means of electrocautery (31%, P = .011). Intraoperative flow measurements and patency rates at 5 days postoperatively were not significantly different among groups.

CONCLUSIONS

Optical coherence tomography provides a level of speed and accuracy for quantifying endothelial injury and vasospasm that has not been described for any other modality, suggesting potential as an intraoperative quality assurance tool. Our optical coherence tomographic findings suggest that the harmonic scalpel induces less spasm and intimal injury compared with electrocautery.

Aneurysm of an autologous aorta to right coronary artery reverse saphenous vein graft presenting as a mediastinal mass: a case report

Aneurysmal dilation of saphenous vein grafts is a relatively rare complication of the now common surgical procedure of coronary artery bypass graft (CABG) surgery. The true prevalence of this condition is not clear, however, literature review by Jorgensen et. al. between 1975 and 2002 revealed only 76 published cases. [1] Recent review of literature, utilizing OVID (search terms: saphenous vein, aneurysm, graft, pseudoaneurysm, coronary bypass) suggests a significantly higher prevalence with 14 such cases published in a variety of multinational journals during the period of 2006 to April 2007. The causes of this dramatic increase is likely multifactorial, however, in the author's opinion, likely reflects the increased sophistication and utilization of cross sectional imaging modalities. Regardless of the true prevalence of the condition, there is little debate that the potential for serious morbidity and mortality in this patient population is significant, and that increased detection and discussion of viable therapeutic options is critical. [1] Therefore, we present a case report and discussion of a patient with symptomatic cardiac ischemia, found to have a large saphenous vein graft aneurysm (SVGA) on coronary CTA.

Cardiac multi-detector CT: its unique contribution to cardiology practice

Medical practice is moving fast towards non-invasive and non-surgical disease management. While significant progress has been made with coronary artery disease prevention, MDCT stands as an ideal non-invasive tool for its progression. It accurately assesses both arterial lumen and wall disease. Although the main concern of current cardiology practice is the coronary stenotic disease, arterial wall calcification itself may significantly contribute to patients' symptoms. Thus, in addition to the beneficial use of MDCT in patients with mild to moderate risk for coronary disease, the unique information it provides on wall disease may assist the management of symptomatic patients with no flow-limiting lesions.

Perioperative management of aspirin resistance after off-pump coronary artery bypass grafting: possible role for aprotinin

BACKGROUND

Aspirin is the only drug proven to reduce saphenous vein graft (SVG) failure, but aspirin resistance (ASA-R) frequently occurs after off-pump coronary artery bypass grafting (OPCAB). The factors, mechanism, and best means for preventing and/or treating ASA-R have not been established. This study hypothesizes that thrombin production during OPCAB stimulates this acquired ASA-R.

STUDY DESIGN AND METHODS

A nonrandomized prospective cohort of 255 patients (n=465 SVG) who underwent OPCAB with varied use of aprotinin (21%) and different SVG preparation techniques (standard, 56% vs. low-pressure, 44%) was analyzed. A surplus SVG segment was obtained to assess endothelial integrity. ASA-R was determined at baseline, after surgery, and on Days 1 and 3 by three assays. The effects of aprotinin on thrombin responsiveness were analyzed by means of whole-blood aggregometry, SVG tissue factor (TF) activity, and transcardiac thrombin production (i.e., F1.2 levels in aorta versus coronary sinus). SVG patency was assessed on Day 5 with multichannel CT angiography.

RESULTS

ASA-R developed in 42 percent of patients after OPCAB. Multivariate analysis showed that ASA-R, endothelial integrity, and target size independently predicted early SVG failure. Aprotinin use was associated with: 1) reduced postoperative ASA-R (15%); 2) decreased platelet (PLT) response to thrombin; 3) reduced TF activity within SVG segments; 4) decreased transcardiac thrombin gradient; and 5) improved SVG patency.

CONCLUSION

ASA-R is a common post-OPCAB event whose frequency may be reduced by intraoperative use of aprotinin, possibly via TF and thrombin suppression. Improved perioperative PLT function after OPCAB may also inadvertently enhance the clinical relevance of these potential antithrombotic effects.

Optical coherence tomography imaging as a quality assurance tool for evaluating endoscopic harvest of the radial artery

BACKGROUND

Concerns about intimal disruption and spasm have limited enthusiasm for endoscopic radial artery harvest (ERAH), although the risk of these problems after this procedure remains uncertain. Radial artery conduits were screened intraoperatively before and after ERAH vs open harvest using catheter-based high-resolution optical coherence tomography (OCT) imaging.

METHODS

Twenty-four cadavers and 60 coronary artery bypass graft (CABG) patients scheduled to receive a RA graft underwent OCT imaging before (in situ) and after (ex vivo) open harvest or ERAH. Spasm was quantified by the percentage change in luminal volume between images. Intimal disruption was classified as minor or severe depending on whether the defect was confined to branch ostia or involved the luminal surface. Histology was used to confirm OCT findings.

RESULTS

Luminal volume significantly declined after harvest in all RAs from CABG patients, but there was no difference between groups: -43% +/- 29% vs -35% +/- 38% change after ERAH (n = 21) vs open harvest (n = 39; p = 0.342). Significantly more intimal injury was noted after ERAH vs open harvest (34/41 vs 9/43, intimal tears/total evaluated RAs, p < 0.0001). Most intimal injury was minor: only 2 tears involved the luminal surface of the RA (both after ERAH). Serial imaging in cadavers revealed that 86% of ostial tears occur in ERAH during the initial blunt dissection step using the endoscope.

CONCLUSIONS

Although branch injury is a pitfall of ERAH, OCT imaging documented that the quality of RA procured is acceptable and comparable with open harvest. Catheter-based OCT provides an important quality assurance tool for RA harvest.

Simultaneous "hybrid" percutaneous coronary intervention and minimally invasive surgical bypass grafting: feasibility, safety, and clinical outcomes

Surgical and percutaneous coronary artery intervention revascularization are traditionally considered isolated options. A simultaneous hybrid approach may allow an opportunity to match the best strategy for a particular anatomic lesion. Concerns regarding safety and feasibility of such an approach exist. We examined the safety, feasibility, and early outcomes of a simultaneous hybrid revascularization strategy (minimally invasive direct coronary bypass grafting of the left anterior descending [LAD] artery and drug-eluting stent [DES] to non-LAD lesions) in 13 patients with multivessel coronary artery disease that underwent left internal mammary artery to LAD minimally invasive direct coronary bypass performed through a lateral thoracotomy, followed by stenting of non-LAD lesions, in a fluoroscopy-equipped operating room. Assessment of coagulation parameters was also undertaken. Inhospital and postdischarge outcomes of these patients were compared to a group of 26 propensity score matched parallel controls that underwent standard off-pump coronary artery bypass. Baseline characteristics were similar in both groups. All hybrid patients were successfully treated with DES and no inhospital mortality occurred in either group. Hybrid patients had a shorter length of stay (3.6 +/- 1.5 vs 6.3 +/- 2.3 days, P < .0001) and intubation times (0.5 +/- 1.3 vs 11.7 +/- 9.6 hours, P < .02). Despite aggressive anticoagulation and confirmed platelet inhibition, hybrid patients had less blood loss (581 +/- 402 vs 1242 +/- 941 mL, P < .05) and decreased transfusions (0.33 +/- 0.49 vs 1.47 +/- 1.53 U, P < .01). Six-month angiographic vessel patency and major adverse cardiac events were similar in the hybrid and off-pump coronary artery bypass groups. A simultaneous hybrid approach consisting of minimally invasive coronary artery bypass grafting with left internal mammary artery to LAD combined with revascularization of the remaining coronary targets using percutaneous coronary artery intervention with DES is a feasible option accomplished with acceptable clinical outcomes without increased bleeding risk.

Simultaneous hybrid coronary revascularization reduces postoperative morbidity compared with results from conventional off-pump coronary artery bypass

OBJECTIVES

Less-invasive options are available for surgical treatment of multivessel coronary artery disease. We hypothesized that stenting combined with grafting of the left anterior descending artery with the left internal thoracic artery through a minithoracotomy (hybrid procedure) would provide the best outcome.

METHODS

Patients with equivalent numbers of coronary lesions (2.8 +/- 0.4) underwent either hybrid (n = 15) or off-pump coronary artery bypass through a sternotomy (n = 30). Early and 1-year outcomes were compared. Blood drawn from the aorta and coronary sinus immediately postoperatively was analyzed for activation of coagulation (prothrombin fragment 1.2 and activated Factor XII), myocardial injury (myoglobin), and inflammation (interleukin 8) by using an enzyme-linked immunosorbent assay. Target-vessel patency was determined by means of computed tomographic angiographic analysis.

RESULTS

The hybrid procedure was associated with significantly shorter lengths of intubation and stays in the intensive care unit and hospital and perioperative morbidity (P < .05). Intraoperative costs were increased but postoperative costs were reduced for the hybrid procedure compared with off-pump coronary artery bypass through a sternotomy. As a result, overall total costs were not significantly different between the groups. After adjusting for potential confounders, assignment to the hybrid group was an independent predictor of shortened time to return to work (t = -2.12, P = .04). Patient satisfaction after the hybrid procedure, as judged on a 6-point scale, was greater versus that after off-pump coronary artery bypass through a sternotomy. Finally, the hybrid procedure showed significantly reduced transcardiac gradients of markers of coagulation, myocardial injury, and inflammation and a trend toward significant improvement in target-vessel patency.

CONCLUSIONS

Perhaps because of reduced myocardial injury, inflammation, and activation of coagulation, patients undergoing the hybrid procedure had better perioperative outcomes and satisfaction, with excellent patency at 1 year's follow-up. These promising preliminary findings warrant further investigation of this procedure.

Strategies to reduce intraluminal clot formation in endoscopically harvested saphenous veins

OBJECTIVE

Residual clot strands within the excised saphenous vein are an increasingly recognized sequela of endoscopic vein harvest. We hypothesized that endoscopic visualization facilitated by sealed carbon dioxide insufflation causes stagnation of blood within the saphenous vein. In the absence of prior heparin administration, this stasis provokes clot formation.

METHODS

Forty consecutive patients having coronary artery bypass grafting underwent endoscopic vein harvest using sealed (Guidant VasoView, n = 30; Guidant Corp, Minneapolis, Minn) or open (Datascope ClearGlide, n = 10; Datascope Corp, Montvale, NJ) carbon dioxide insufflation followed by ex vivo assessment of intraluminal saphenous vein clot via optical coherence tomography. In the sealed carbon dioxide insufflation groups, clot formation was compared with (preheparinized, n = 20) and without (control, n = 10) heparin administration before endoscopic vein harvest, either at a fixed dose or titrated to an activated clotting time greater than 300 seconds. Risk factors for clot formation were assessed.

RESULTS

Residual saphenous vein clot was a universal finding in control veins (sealed carbon dioxide insufflation endoscopic vein harvest without preheparinization). At either dose used, heparin given before endoscopic vein harvest significantly decreased saphenous vein clot burden. A similar reduction in clot was observed when using open carbon dioxide insufflation endoscopic vein harvest without preheparinization. Intraoperative blood loss and blood product requirements were similar in all groups. Patient age and preoperative maximum amplitude of the thrombelastography tracing showed a linear correlation with saphenous vein clot volume.

CONCLUSION

By enabling the quantification of this issue as never before possible, optical coherence tomography screening revealed that intraluminal saphenous vein clot is frequently found after endoscopic vein harvest. Systemic heparinization before harvest or an open carbon dioxide endoscopic vein harvest system are benign changes in practice that can significantly lessen this complication.

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

Multi-detector row CT (MDCT) scanners with high spatial and temporal resolutions are now available and are increasingly used for non-invasive assessment of vascular disease, including coronary arteries and coronary artery bypass grafts (CABG). Follow-up of patients who have previously undergone surgical revascularization for coronary artery disease is nowadays one of the main applications of MDCT. Thanks to the continuous technical evolution of the CT scanners, it is now possible to scan the heart and the full anatomic extent of grafts with sub-millimeter slice-thickness within a single breath-hold. In the evaluation of these patients, it is important for the radiologist to be familiar with the different types of grafts and surgical techniques to know the main characteristics of each graft type and what to look for in the assessment of a patient who has undergone coronary artery surgical revascularization. This review summarizes some surgical aspects, the biological characteristics of conduits, and the main technical MDCT features, and describes the CABG anatomy together with some typical CT findings.

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

PURPOSE

The aim of this study was to define the role of multidetector computed tomography (MDCT) in the follow-up assessment of patients undergoing coronary artery bypass grafting (CABG) using an evidence-based medicine (EBM) approach.

MATERIALS AND METHODS

We performed a literature search of the most reputable studies published in the period 1990-2005 on the clinical follow-up of patients after myocardial revascularisation by CABG. Relevant studies were ranked according to levels of evidence using EBM criteria. A similar search was also conducted on the Internet to identify and review the guidelines posted by the major international scientific societies.

RESULTS

A total of 29 papers meeting the basic reliability requirements of EBM were identified. The reported sensitivity and specificity for electrocardiogram (ECG) testing, stress echocardiography and radionuclide myocardial perfusion imaging were 45% and 82%, 86% and 90%, and 68% and 84%, respectively. All 16 CT studies (one retrospective, the remaining prospective) were validation studies comparing MDCT with conventional coronary angiography. The total number of patients and graft segments studied were 705 and 1,974, respectively. The total number of assessable graft segments were 62%-100%, with a sensitivity and specificity of 75%-100% and 76.9%-100%, respectively.

CONCLUSIONS

The applications of MDCT in the follow-up assessment of patients after CABG are derived from indirect evidence only. The efficacy of the method should be evaluated in randomised clinical trials comparing MDCT not only with conventional coronary angiography but also with other noninvasive stress imaging methods. On the basis of the clinical evidence reported in the literature, the indications for the use of MDCT are still limited. In our view, the completion of such randomised trials combined with the development of new-generation scanners is required to correctly define the role of MDCT in the follow-up assessment of patients who have undergone CABG.

Midterm follow-up of patients receiving radial artery as coronary artery bypass grafts using 16-detector-row CT coronary angiography

PURPOSE

The study was undertaken to evaluate the 3-year outcome of patients undergoing coronary artery bypass grafting (CABG) involving the use of the radial artery (RA) in comparison with the left internal mammary artery (LIMA) and saphenous vein (SV) grafts by using 16-slice multidetector computed tomography (MDCT).

MATERIALS AND METHODS

Fifty-one patients underwent electrocardiogram (ECG)-gated 16-MDCT 32+/-4 months after surgery. A total of 50 LIMA grafts, 55 SV grafts and 51 RA grafts were studied. Approximately 68.6% or RAs were free, 21.5% sequential and 9.8% composite. Grade 0 was defined as complete patency, grade 1 as focal stenosis (>70%) and grade 2 as graft occlusion. The Fisher exact test was used to analyse variables (p<0.05 significant). Concordance between readers for the detection of patency was calculated by the kappa-value.

RESULTS

LIMA had the best patency rate (94.0%), followed by SV (83.6%) and RA (74.5%). Regarding RA, the patency rate by territory was 79.4% in the left circumflex coronary artery (LCX), 72.7% in the left anterior descending (LAD) and 50% in the right coronary artery (RCA); the occlusion rate was 20.0% among free grafts, 18.2% among sequential grafts and 20.0% among composite grafts. The kappa-value was 0.86.

CONCLUSIONS

Sixteen-slice MDCT scanners enable accurate analysis of CABG status and are a useful noninvasive diagnostic tool for midterm clinical follow-up of patients who have undergone CABG involving the use of RA.

Prevalence of significant noncardiac findings on coronary multidetector computed tomography angiography in asymptomatic patients

PURPOSE

The purpose of the present study was to determine the prevalence of significant noncardiac findings in asymptomatic patients undergoing coronary multidetector computed tomography (MDCT) angiography.

MATERIALS AND METHODS

A total of 258 consecutive participants, 202 (78.3%) men and 56 (21.7%) women, aged 54.38 +/- 7.9 years (range, 40-86 years), underwent CT of the coronary arteries. All examinations were performed with the 16-slice Brilliance CT scanner (Philips, Cleveland, Ohio) and electrocardiography triggering. Patients were scanned in the supine position twice, first without contrast medium to calculate the calcium score and then with contrast medium.

RESULTS

One hundred forty-five patients (56.2%) were found to have a significant noncardiac abnormality on coronary MDCT angiography. Lung abnormalities were detected in 91 patients. Eleven patients had emphysema, 17 with bullae, 3 with interstitial lung disease, 3 with lung mass of more than 10 mm, and 64 with lung nodules. Pericardial abnormalities were identified in 10 patients (3.8%). Liver disease was detected in 12 patients (16.9%), including multiple cysts and echinococcal cyst, and 5 patients had liver mass. Adrenal masses were found in 8 patients (one with 2 masses). Bone abnormalities were found in 3 patients, one with sclerotic lesion in the vertebral body, one with osteolytic lesion in the fifth rib, and one with bilateral cervical rib.

CONCLUSIONS

In the present study, 56.2% of asymptomatic patients undergoing coronary MDCT angiography were found to have significant extracardiac pathology requiring additional workup. Therefore it is essential that a radiologist should review the scans for abnormalities in structures other than the coronary arteries.

Noninvasive Midterm Follow-Up of Radial Artery Bypass Grafts With 16-Slice Computed Tomography

BACKGROUND

The standard invasive procedure to evaluate graft patency is selective coronary angiography. The recent introduction of a new generation of multidetector row computed tomography made possible the noninvasive study of grafts with excellent results in terms of visualization and resolution. We used computed tomography to study all patients with a radial artery graft operated on in 2002.

METHODS

Between April and October 2005, we reviewed all patients operated on by coronary artery bypass grafting at our institution between January and December 2002. A total of 62 patients received a radial artery graft. Of these, 22 were lost at the time of follow-up. The other 40 patients were enrolled for a multidetector row computed tomography study. Demographic and instrumental data were collected for all the patients. A total number of 145 grafts were studied, with complete and excellent visualization.

RESULTS

The scans revealed a 97.77% (44 of 45) patency rate for left internal mammary arteries, 90.57% (48 of 53) for vein grafts, and 73.91% (34 of 46) for radial arteries (mammary artery plus vein grafts versus radial artery patency, p < 0.001). If analyzed for target vessel, we found the poorest result of radial grafts when placed on the right coronary artery (40% [2 of 5] patency rate).

CONCLUSIONS

Noninvasive control of previously bypassed patients is feasible, with no discomfort for them and excellent visualization of grafts. The use of the radial artery as a conduit for bypass graft can be achieved with good results, after a careful choice of the target vessel.

Cardiac imaging using multislice computed tomography scanners: technical considerations

Conventional coronary angiography is currently the gold standard in the detection and diagnosis of coronary artery disease. This modality, however, is invasive in nature. Hence, there is a need for noninvasive imaging techniques to provide comprehensive assessment of coronary artery disease, especially in stable patients at low to moderate risk of disease. In recent years, a number of noninvasive modalities have found wide applications in cardiac imaging. Most recent investigations have used magnetic resonance imaging, multislice computed tomography and electron-beam computed tomography scanners. This review discusses the clinical challenges existing in the field of cardiac imaging and focuses on the technical advancements of multislice computed tomography scanners that have made them a very attractive noninvasive option for the detection and diagnosis of coronary artery disease.

Endothelial injury and acquired aspirin resistance as promoters of regional thrombin formation and early vein graft failure after coronary artery bypass grafting

OBJECTIVE

The predominant mechanism of early graft failure after coronary artery bypass grafting remains in doubt. Aspirin administered in the initial hours after coronary artery bypass grafting improves graft patency, implicating prostanoid synthesis in the pathogenesis. We hypothesized that synergy between endothelial disruption in the venous conduit and aspirin resistance would cause vein graft failure.

METHODS

Aspirin resistance, defined by diagnostic findings on at least two of three separate assays, was serially assessed in 225 patients undergoing off-pump coronary artery bypass grafting. Endothelial cell integrity was determined in surplus segments obtained from 408 vein grafts. The deposition of intraluminal thrombin within the vein was determined by comparing serum F1.2 levels between the coronary sinus and the aorta after grafting. Intraoperative blood flow in the grafts was measured with transit-time technology, and patency was assessed with electrocardiographically gated multichannel computed tomographic coronary angiography on day 5. Aspirin was the sole antithrombotic agent used during the study.

RESULTS

Thrombosed grafts (16/408) showed more endothelial cell loss at the time of grafting than did those grafts that remained patent (10.8% +/- 21.5% vs 51.4% +/- 39.1% integrity, P < .01). Aspirin resistance occurred in 67 patients (30%). Graft thrombosis was associated with aspirin resistance (P < .04) and reduced endothelial integrity (P < .01). These factors coexisted in 14 of 16 grafts that failed and were associated with elevated coronary sinus F1.2 levels.

CONCLUSION

Aspirin resistance and relatively compromised venous endothelial cell integrity together marked patients whose vein grafts failed within days after off-pump coronary artery bypass grafting. These observations form a basis for identifying patients at risk and developing approaches to prevent vein injury or to selectively intervene in high-risk circumstances.