Journal of Vascular Surgery
Volume 48, Issue 3 , Pages 561-570, September 2008

Simultaneous sizing and preoperative risk stratification for thoracic endovascular aneurysm repair: Role of gated computed tomography

  • Felix J.V. Schlösser, MD

      Affiliations

    • Section of Vascular Surgery, Yale University, New Haven, Conn
    • ,
  • Hamid R. Mojibian, MD

      Affiliations

    • Department of Radiology, Yale University, New Haven, Conn
    • ,
  • Alan Dardik, MD, PhD

      Affiliations

    • Section of Vascular Surgery, Yale University, New Haven, Conn
    • ,
  • Hence J.M. Verhagen, MD, PhD

      Affiliations

    • Department of Vascular Surgery, Erasmus Medical Center, Rotterdam, The Netherlands
    • ,
  • Frans L. Moll, MD, PhD

      Affiliations

    • Department of Vascular Surgery, Utrecht Medical Center, Utrecht, The Netherlands
    • ,
  • Bart E. Muhs, MD, PhD

      Affiliations

    • Section of Vascular Surgery, Yale University, New Haven, Conn
    • Corresponding Author InformationReprint requests: Bart E. Muhs, MD, PhD, Assistant Professor of Surgery, Co-Director of Endovascular Surgery, Yale University School of Medicine, Section of Vascular Surgery, 333 Cedar St, FMB-137, New Haven, CT 06510

Received 4 February 2008; accepted 24 April 2008. published online 01 July 2008.

Article Outline

Objectives

Risk factors are similar for the development of both thoracic aortic aneurysms (TAA) and other cardiovascular diseases. Coronary artery disease is highly prevalent in patients with TAA, with a reported prevalence of 30% to 70%. Knowledge of the underlying cardiac pathology can minimize perioperative risk and improve patient selection. This study investigated the feasibility of simultaneous assessment of thoracic aortic pathology and cardiac structures and function, including the coronary arteries, using electrocardiogram-gated 64-slice computed tomography (CT) angiography.

Methods

ECG-gated 64-detector row CT examinations of 11 patients (8 men, 3 women; mean age, 67 ± 16; range, 41-83 years) with thoracic aortic pathology, including aneurysms and dissections, were reviewed. Images were assessed for coronary artery disease, calcifications, cardiac function, and valve characteristics. Simultaneous assessment and measurements of thoracic aortic pathology were performed with the same scan.

Results

All images of the patients could be successfully assessed for calcium scores, coronary artery stenoses, coronary artery anomalies, interventricular septal wall thickness, myocardial scar, left ventricular ejection fraction, muscle mass, and aortic and mitral valve calcification, mobility, and valve anatomy. Diagnostic image quality was also achieved in all patients for the underlying thoracic aortic disease.

Conclusion

This study introduces the feasibility of dynamic imaging of the thoracic aorta and cardiac structures and function, including the coronary arteries, with just one CT scan. The images could be successfully assessed for thoracic aorta pathology, cardiac disease, and extracardiac pathology. With further developments of CT scanners—and more detailed insight in the prognosis of patients based on ECG-gated CTA findings—this new technique may become the initial imaging modality for preoperative cardiac risk stratification in patients with TAAs or dissections.

 

Atherosclerosis often presents as a multifocal disease. Risk factors are similar for the development of both thoracic aortic aneurysms (TAAs) and other cardiovascular diseases. Coronary artery disease is common in patients with TAAs, with reported prevalences of 30% to 70%.1, 2, 3, 4, 5 Attention is often focused on the aortic pathology, but other vascular diseases, especially cardiac diseases, can be important risk factors for surgical morbidity and mortality.

The Swedish Heart Surgery registry revealed that 43% of the perioperative patient deaths in those undergoing surgery for aortic aneurysm or dissection resulted from a cardiac cause.6 Coronary artery disease is a significant risk factor for death after thoracic aortic repair.2, 3, 7 Congestive heart failure and a reduced left ventricular ejection fraction of <50% have also been reported to be significant risk factors for short- and long-term mortality after thoracic aortic repair.2, 8 Knowledge of underlying potentially significant cardiac pathology preoperatively can improve predictions of patient prognosis and patient selection for surgery, and subsequently lead to improved patient prognosis after surgery.

The risk of thoracic aortic surgery is high. Rigberg et al9 reported patient mortality rates of 19% at 30 days and 31% at 1 year for elective thoracic aortic surgery in a national registry study. Mortality for ruptured cases was even higher, with 48.4% at 30 days and 61.5% at 1 year. The surgeon has to balance the risks of surgery against the risks of the natural course of the disease.

Patients with coronary artery disease and other cardiac pathologies are often asymptomatic; therefore, preoperative diagnosis is important for detection of underlying diseases. Elective diagnostic coronary angiography is most often performed by invasive cardiac catheterization. In the United States, 91% of all cardiac catheterizations are performed electively, and 40% of all cardiac catheterizations show normal findings, without coronary artery disease.10

A new imaging modality, electrocardiogram (ECG)-gated computed tomography angiography (CTA), has undergone an enormous evolution during recent years, and its role as a diagnostic imaging modality in clinical care is rapidly expanding. ECG-gated CT has several important advantages compared with nongated CTs. Imaging with ECG-gated CTA enables the clinician to obtain images at different phases of the cardiac cycle. This is especially important in the planning of endovascular procedures where precise sizing of the graft is required.11, 12 Muhs et al13 studied thoracic aortic dynamics with ECG-gated 64-slice CTA and reported large changes of the aortic diameter throughout the cardiac cycle, up to 17.8%. ECG-gated CT can be especially beneficial for patients suspected of thoracic aortic dissections. Motion artifacts often cause false-positive detections of thoracic aortic dissection in nongated CT images. When ECG-gating is used, the effect of motion artifacts is minimal, and diagnostic accuracy improved.14

Cardiac motion causes motion artifacts when ECG-gating is not used because of movement of the heart and aorta in all three spatial dimensions during the cardiac cycle.15 As has been described earlier, ECG-gating can be performed to acquire images at specific time intervals of the cardiac cycle.

ECG-gated CT imaging can be divided into two techniques: prospective and retrospective gating. When prospective gating is used, images are acquired at a predefined portion (or portions) of the cardiac cycle. In comparison, when retrospective gating is used, images are acquired continuously throughout the cardiac cycle, with simultaneous digital recording of ECG information. An advantage of retrospective gating is that images can be reconstructed for any moment throughout the cardiac cycle. Retrospective gating is therefore usually used for visualization of the thoracic aorta.16 Almost all patients in whom thoracic aortic surgery is planned already undergo CT scanning with contrast during the workup for imaging of the TAA or dissection. ECG-gated CT may be a perfect replacement of the regular CT study in clinical care for patients undergoing thoracic aortic surgery, because one scan per patient may be sufficient for both thoracic aorta visualization and obtaining data about cardiac structures and function. This study investigated the feasibility of simultaneously assessing thoracic aortic pathology as well as cardiac structures and function, including the coronary arteries, with ECG-gated 64-slice CT angiography.

Back to Article Outline

Methods 

Patient selection 

The Picture Archiving and Communication System (PACS) of Yale-New Haven Hospital was searched for ECG-gated CT scans that were made in patients with thoracic aortic pathology. All these scans were retrospectively reviewed and selected for inclusion in our cohort. The study was approved by the local Human Investigations Committee.

Scanning parameters 

All scans were performed on a 64-slice multidetector CT: either GE VCT (Milwaukee, Wis) or Toshiba Aquilion (Tokyo, Japan) scanners. Subjects were horizontally placed on the table and an 18-gauge intravenous access was established in the right antecubital fossa. Initially, noncontrast images from the level of the neck base to the upper abdomen were performed for evaluation of aortic calcification, intramural hematoma, and coronary artery calcification. Noncontrast scans were followed by acquisition of 0.625-mm-thick retrospectively gated axial images during infusion of 100 to 140 mL of iodixanol (Visipaque, General Electric Healthcare, Princeton, NJ), followed by saline infusion.

Scans were performed from the level of the neck base to the level of the common femoral arteries. To minimize the radiation dose, ECG-modulated tube current modulation was applied. The gantry rotation time and pitch were selected according to the patient's heart rate and the recommendation of the scanner manufacturer. Optimal contrast timing was determined with a bolus tracking method with the region of interest positioned on the descending aorta at the level of the main pulmonary artery.

Image reconstruction 

The acquired contrast images were retrospectively reconstructed in two data sets. Images in the first group were reconstructed from the level of the neck base to the level of the origin of the celiac artery in 10% steps throughout the cardiac cycle, from 0% to 90%. and with a slice thickness of 0.625 mm. Images of the chest, abdomen, and pelvis were reconstructed with a slice thickness of 2.5 mm at 75% of the cardiac cycle. All images were sent to Vitrea 2.0 (Vital Images, Minneapolis, Minn) for postprocessing.

Lesion detection and grading 

The coronary calcium score (CCS) was initially calculated according to the Agatston scoring system, which is based upon the number of calcium deposits and the density of these deposits.17 Precontrast images were used for the calculation of the CCS. The 0.625-mm data sets at different phases of the cardiac cycle were examined, and the phases with least motion artifact were chosen. Calculated CCSs were compared by software with average age- and sex-stratified calcium scores to determine a CCS risk percentile for the patient. Multiplanar reformation, curved-planar reformation, and maximum intensity projection images were generated, and segments of left main coronary artery, left anterior descending coronary artery, left circumflex coronary artery, and right coronary artery were evaluated for congenital anomalies, atherosclerotic plaque, and any significant stenoses.

In a semiautomated fashion, the dynamic images from 0% to 90% of the cardiac cycle were used to calculate stroke volume (end-diastolic volume − end-systolic volume), and ejection fraction (ejection fraction = stroke volume/end-diastolic volume), septal wall thickness, myocardial mass of the left ventricle, assessment of the wall motion, valve visibility, number of valve leaflets, valve motion, and valve calcification. At the same time, dynamic aortic measurements were performed. The 2.5-mm-thick images were used to evaluate extra-cardiovascular findings. All studies were reviewed and analyzed by a radiologist (H. R. M.) with cardiovascular imaging training and >2 years of cardiac imaging experience.

Back to Article Outline

Results 

ECG-gated CT images were performed in 11 patients (8 men, 3 women) with a mean age of 67 ± 16 years (range, 41-83 years). The excellent spatial resolution (0.625 mm) combined with the retrospective ECG-gating allowed precise and dynamic structural evaluation of the thoracic aorta. Aneurysms or dissections were found in most patients. A large vessel vasculitis was demonstrated in one patient. The retrospective ECG-gating provided the opportunity to determine sizes of the thoracic aortic pathology throughout different phases of the cardiac cycle. All images could be successfully assessed for the pathologic lesions of the thoracic aorta. The details of the location and maximal dimensions of the thoracic aortic lesions are shown in the Table.

Table. Characteristics provided by the gated computed tomography images
Thoracic aortaCardiac characteristics
Patient No.Sex, age (y)CADCCSCCS PCTLaEF (%)MM (g)WT (mm)Aortic valveMitral valve VISOtherLung
NSpecsVisbN VLCalc
1F,43Aneurysm of the ascending aorta and proximal aortic arch, 48 × 44 mm0. . .0<256112810++3No++. . .. . .
2F,52Aneurysm of the ascending aorta, 41 × 42 mm; aneurysm of the descending aorta 42 × 43 mm0. . .0<25691309++3No++. . .. . .
3F,82Aneurysm of the ascending aorta, 63 × 57 mm; dissection in ascending aorta, no coronary artery involvement1LAD0<252413713+3Minimal+Heart chambers enlargedPulmonary vascular congestion
4M,41Dissection flap in ascending aorta extending to proximal descending aorta, distal to LSA; aneurysm of the descending aorta, 43 × 24 mm; remnant of ductus arteriosus visible0. . .0<255913310++PAVNo++CABG (2×, patent, no stenosis). . .
5M,59Dissection in ascending aorta, dissection flap extending to distal to LSA1LCx640/603>90. . .13111++3Minimal++. . .. . .
6M,68Aneurysm of the descending aorta, 45 × 42 mm3LCx, LAD, RCA698/90975-902417111++3No+CABG (1×), subendocardial scar tissueLeft apical mass, high suspicion of malignancy
7M,74Large vessel vasculitis of the ascending aortic, aortic arch extending to distal of LSA.0–53/7620-304713312++3No+. . .. . .
8M,75Descending aortic aneurysm, 59 × 55 mm2LAD, LCx439/36250-752912110++3No++. . .. . .
9M,81Aneurysm of the aortic arch, 70 × 65 mm extending to descending aorta, 50 × 48 mm2LAD, LCx882/72975-90529710++3Minimal++. . .. . .
10M,83Dissection of the descending aorta with several pseudoaneurysms, mediastinal hematoma3LMCA, LAD, RCA172/20740-505114115+3No+. . .. . .
11M,83Aneurysm of the aortic arch extending to descending aorta, 66 × 62 mm2LAD, RCA116/14925-504111510+3Minimal+Thrombus in left atrial appendix. . .

CABG, Coronary artery bypass graft; CAD, Coronary artery disease; Calc, calcification; CCS PCTL, risk percentile of coronary calcium score; CCS, coronary calcium score; EF, ejection fraction; LAD, left anterior descending coronary artery; LCx, circumflex branch of the left coronary artery; LMCA, left main coronary artery; LSA, left subclavian artery; MM, myocardial muscle mass; PAV, prosthetic aorta valve; RCA, right coronary artery; Specs, specifications; VIS, visibility; VL, valve leaflets; WT, septal wall thickness.

aThe presented percentiles represent the percentage of people with the same age and gender of the presented patient with a lower calcium score.

bValve visibility: + = medium; + + = good.

The obtained images were systematically assessed for cardiac pathology. The coronary calcium deposits were extensive (CCS, >400) in 4 patients, moderate (CCS, 101 to 400) in 2 patients, mild (CCS, 1 to 100) in 1 patient, and the other 4 patients had no detectable coronary calcium (CCS, 0). Age- and sex-stratified percentiles of the CCSs were subsequently determined for all patients (Fig 1).

  • View full-size image.
  • Fig 1. 

    Graph shows coronary calcium scores in asymptomatic men. The small red block represents the percentage of people with the same age and sex of the presented patient who have less calcium in the coronary arteries. The relatively high calcium score in combination with other cardiac findings in this patient would be a good indication for referral of the patient to a cardiologist before surgery.

The coronary arteries were analyzed next. The number of diseased coronary arteries, including the left main coronary artery, left anterior descending artery, left circumflex coronary artery, and right coronary artery, could be determined in all patients (Fig 2). Coronary artery disease of one or more vessels was found in 7 patients: 2 had one-vessel disease; 3 had two-vessel disease; and 2 had three-vessel disease; and the other 4 patients had no coronary artery disease. None of the patients had congenital coronary artery anomalies.

  • View full-size image.
  • Fig 2. 

    A, Cross-sectional views of the left anterior descending coronary artery are shown. B, This curved planar reformatted image of the left anterior descending coronary artery shows a heavily calcified and diffusely diseased artery.

Axial images were studied to measure interventricular septal wall thickness. The mean septal wall thickness was 11 ± 1.7 mm (range, 9-15 mm); therefore, none of the patients had significant hypertrophy (>16 mm).18 Cardiac muscle mass could successfully be determined in all patients with a software tool. The mean cardiac muscle mass was 131 ± 18 g (range, 97-171 g).

End-diastolic and end-systolic volumes were also determined by means of a software tool (Fig 3). Stroke volume and ejection fraction were calculated subsequently. The ejection fraction was normal (≥55%) in three patients, mildly reduced (40% to 55%) in four, and severely reduced (<40%) in three patients.19 Unfortunately, the software tool was not able to successfully calculate the end-diastolic and end-systolic volumes in one patient.

  • View full-size image.
  • Fig 3. 

    In a semi-automated fashion, the dynamic images from 0% to 90% of the cardiac cycle were used to calculate ejection fraction (end-diastolic volume minus end-systolic volume) and the end-diastolic myocardial mass of the left ventricle.

Reconstructed images were used to assess the visibility of the aortic and mitral valves. The valves could be visualized in all patients with medium or good image quality (Fig 4). Visibility of the aortic valve was generally better compared with the visibility of the mitral valve. One patient had a prosthetic aortic valve (Fig 5). The other 10 patients had a normal aortic valve with three valve leaflets. Minimal calcification of the aortic valve was visible in four patients. The other seven patients had no calcifications of the aortic valves.

  • View full-size image.
  • Fig 5. 

    A prosthetic valve was found in one patient. The electrocardiogram-gated computed tomography images show the prosthetic valve in two different phases: (A) open during the systolic phase and (B) closed during the diastolic phase of the cardiac cycle.

Several other cardiac findings were documented. Coronary artery bypass grafts were found in two patients. All of these grafts appeared to be patent, and no stenosis was detected. Subendocardial scar tissue was seen on the CT images of one of these patients, possibly due to a prior myocardial infarction. Abnormal enlargement of the heart chambers was noted in one patient. Images of another patient revealed a thrombus mass in the left atrial appendix (Fig 6).

All axial images were also studied for noncardiac findings. This resulted in the detection of a left apical lung mass in one patient that was highly suggestive of a malignancy. A mediastinal hematoma was found in one patient. Pulmonary congestion was seen in another patient. All other patients had no lung or other extracardiac abnormalities. In conclusion, all images could be successfully assessed for thoracic aorta pathology, cardiac disease, and extracardiac pathology. The Table reports detailed information about all findings.

Back to Article Outline

Discussion 

All images could be successfully assessed for coronary artery stenoses, CCSs, coronary artery anomalies, wall thickness, left ventricular ejection fraction (except one patient), end-systolic volumes, end-diastolic volumes, muscle mass, valve visibility, number of valve leaflets, valve motion, and valve calcification. Diagnostic image quality was also achieved in all patients for preoperative staging of the underlying thoracic aortic disease. Therefore, our study shows that the underlying thoracic aortic disease as well as the cardiac function for preoperative risk stratification can be assessed successfully with ECG-gated 64-slice CTA.

Wide implementation for preoperative risk stratification of this novel approach is limited by several factors, however. Evidence about the association between the CCSs and risks of cardiovascular events is limited. The traditional scoring system from Agatston et al17 was performed in this study for coronary artery calcium scoring.17 Raggi et al showed that the CCSs are strongly correlated with atherosclerotic plaque burden and may therefore hypothetically predict future cardiovascular events.20 Arad et al21 significantly and independently associated CT CCSs with cardiovascular disease events in a large prospective cohort study. Recent studies, however, have shown that more quantitative measures, such as absolute calcium volume or mass, may be more accurate and reproducible.22, 23

Several steps are required for successful ECG-gated coronary CTA. Initially, intravenous access and three ECG leads are required. Rate control with β-blockers can be desirable. Usually, the highest possible gantry rotation speed and thinnest slice thickness are chosen. The scanner may optimize the gantry rotation speed depending on the patient's heart rate. Highly concentrated and rapidly injected contrast media can be used to improve vascular enhancement. A small field of view should be chosen to cover the cardiac structures for optimal spatial resolution and a larger field of view to cover the thoracic aorta. This approach is different compared with regular ECG-gated coronary CT, because then a small field of view is chosen only. An additional full field of view can be reconstructed to assess the thorax for extra-cardiovascular lesions. Another difference with regular ECG-gated coronary CTA is that ECG-gated imaging of the aorta requires a longer breath hold than coronary ECG-gated CTA (approximately 10 vs 3 seconds in our experience).

This study showed that these differences do not limit the use of gated CT for imaging of both thoracic aorta and cardiac structures. Analysis of the images can subsequently be performed by review of the axial slices and the use of simple and advanced analysis and visualization tools. An excellent step-by-step manual for successful performance of ECG-gated coronary CTA has been provided by Kerl et al.24 The requirements for establishing a successful cardiac CT clinic have been described by Dowe.10

The size of the field of view that is required for analysis of the thoracic aorta is much larger than the field of view that is required for analysis of the cardiac anatomy and function. Reconstruction of the gated CT images for simultaneous analysis of the thoracic aorta, cardiac anatomy, and cardiac function is a time-consuming procedure at the current state of the art. We succeeded in all patients, but the analysis for each patient took nearly 30 minutes, and the large number of images—between 3000 and 6000 images per patient—may even slow down networks and computers. Optimizing CT reconstruction techniques is important to make the required image analysis more efficient and practical for busy departments.

A meta-analysis of the diagnostic accuracy of gated-CT with 64-slice CT for detection of coronary artery disease has been described by Chartrand et al.25 They reviewed the results of seven articles that compared 64-slice CT with coronary angiography and reported the following diagnostic values for detection of stenoses of >50% with 64-slice ECG-gated CT, compared with coronary angiography: specificity, 91%; sensitivity, 96%; positive-predictive value, 94%; and negative-predictive value, 98% on the basis of a per-patient analysis. Especially the proximal and middle segments of the coronary arteries can be assessed successfully.

Dowe10 reported a 99% successful examination rate defined by diagnostic image quality of all main segments. Delhaye et al26 reported that 88% of all middle and proximal coronary artery segments could be assessed successfully without β-blocker administration, as could 98% of the subgroup of all proximal coronary artery segments. The negative-predictive value of ECG-gated CT in the detection of coronary artery disease is 98%, which is extraordinarily good. Because a negative result from an adequate test almost eliminates the presence of coronary artery disease, gated-CT may become the preferred elective diagnostic coronary angiography technique before invasive catheterization is performed.10

Kim et al27 showed superiority of ECG-gated CT in the imaging of coronary artery anomalies compared with coronary angiography. Fallenberg et al28 reported that the dimensions and location of an aneurysm in the left descending artery could be well visualized with retrospective ECG gating. ECG-gated CTA is also valuable for coronary artery bypass graft assessment. One study described a 100% accuracy of a 16-slice CT in the assessment of patency of saphenous vein bypass grafts.29

The diagnostic accuracy of gated-CT with 64-slice CT for the assessment of cardiac function has been described by other authors. Remy-Jardin et al30 showed that ECG-gated CT demonstrates good accuracy for the assessment of the right ventricular ejection fraction compared with equilibrium radionuclide ventriculography and showed excellent low interobserver variability. Schepis et al31 showed excellent agreement of ECG-gated CT with gated single-photon emission CT (SPECT) for the assessment of left ventricular ejection fraction, with excellent interobserver and intraobserver agreement. Salem et al32 showed that assessment of left and right ventricular function and underlying respiratory disease in patients with respiratory diseases was possible in 92% of patients.32 Yamamuro et al33 compared gated CT with MR and showed good correlation for end-diastolic volume, end-systolic volume, and left ventricular mass.

The feasibility of assessment of valve characteristics and valvular motion has also been described. Aortic valvular motion can be well visualized with use of gated 64-slice CT.34 Alkadhi et al35 showed the feasibility of good visualization of the dimensions and movement of the mitral valve with gated CT. Interobserver agreement was classified as good to excellent.

A unique advantage of ECG-gated CTA, which most other cardiac tests are lacking, is the opportunity to study images for extracardiac findings, including pathology of lungs (eg, nodules or pulmonary embolism), mediastinum, thorax wall, and upper abdomen.36 These findings may be clinically important and lead to treatment changes to improve the prognosis of these patients.

ECG-gated CT has several limitations, however. One disadvantage of gated CT is that the technique is associated with increased radiation exposure, which is three to four times higher than exposure from a regular nongated CTA.37 The average radiation dose of one ECG-gated CTA could hypothetically cause a fatal malignancy in a very small number of patients.38 Radiation exposure can be significantly reduced by ECG-gated tube current modulation.39, 40 Future techniques are likely to substantially reduce the radiation dose.41 For comparison purposes, reported radiation doses for coronary CTA with radiation reduction by use of tube current modulation ranges from 5.4 to 9.4 mSv.42 The radiation exposure is less than the exposure from a SPECT sestamibi or thallium stress test.10

Another limitation is that the technique is not suitable for patients with irregular pulse or tachycardia. Motion artifacts still have a negative impact on the image quality, despite the improvements in temporal and spatial resolution. Superior imaging results are acquired in patients with heart rates <80 beats/min.26, 43 Despite the improvements in image quality, administration of β-blockers may still be required to improve the quality of coronary imaging by means of slowing the pulse rate.44 Another disadvantage is that obesity and severe calcifications may reduce the image quality, even when a 64-slice CT system is used.45

The small risk of radiation exposure and contrast administration limits the implementation of the test in large screening studies for coronary artery disease in the general population.46 Patients undergoing thoracic aortic repair are, however, different and have a higher a priori risk of coronary artery disease than individuals from the general population. Another difference is that the ECG-gated CT can be performed instead of the regular nongated CTA, which almost all of these patients would undergo otherwise. Increases of risks of radiation and contrast are therefore minimal in our described patient population.

The excellent negative-predictive value of ECG-gated CTA makes the presence of atherosclerotic plaque very unlikely.47 Therefore, the rare but significant risks of invasive coronary angiography can be prevented in many patients. If coronary artery disease or other cardiac lesions are demonstrated on the CTA images, additional tests may be required. The ECG-gated CT may still have provided valuable information. Detailed information about the coronary anatomy may be valuable for the planning of bypass grafting or minimally invasive endovascular cardiac interventions.

Cardiac structures are acquired automatically during ECG-gated CT of the thoracic aorta. Neglect of this free additional information about cardiac structures and function, including the coronary arteries, would be a missed opportunity to detect underlying pathology. Because risks are not increased compared with conventional care, screening can be performed in all patients for whom thoracic aortic surgery is planned, including patients without known risk factors or a history of cardiovascular disease. This may increase the detection rate of cardiac pathology dramatically. Although many of these lesions may have been silent, they may expose the patient to a great risk during extensive surgery. Vascular surgeons should strongly urge that the radiologist provide information about the cardiac structures and function when ECG-gated CTA of the thoracic aorta is requested. The radiologist may not be fully aware that the images can be obtained with the same scan and that the images provide more useful information for the vascular surgeon than the data about the thoracic aorta only. If the radiologist is requested to evaluate the cardiac function, the associated responsibility of the radiologist is likely to increase too.

Despite the advantages of ECG-gated CT and its potential for risk prediction, no studies are yet available that directly associate ECG-gated CT findings with postoperative morbidity and mortality.47 To provide more insight into the predictive characteristics of the ECG-gated CTA findings on postoperative outcome in order to optimize treatment strategies, future well-designed studies are required. The impact on health care costs of ECG-gated CTA will be limited in patients with TAA or dissections because they are already likely to undergo CTA examination in regular conventional care. With further developments of CT scanners, and more detailed insight in the prognosis of patients based on ECG-gated CTA findings, this new technique may become the initial imaging modality for preoperative cardiac risk stratification in many patients with thoracic aortic aneurysms or dissections.

Back to Article Outline

Conclusion 

This study introduces the feasibility of dynamic imaging of the thoracic aorta and cardiac structures and function including the coronary arteries with just one CT scan. The images could be successfully assessed for thoracic aorta pathology, cardiac disease, and extracardiac pathology. Available literature shows that ECG-gated CTA is an excellent test for excluding coronary artery disease. With further developments of CT scanners, and more detailed insight in the prognosis of patients based on ECG-gated CTA findings, this new technique may become the initial imaging modality for preoperative cardiac risk stratification in many patients with TAAs or dissections.

Back to Article Outline

Author contributions 


Conception and design: FS, HM, AD, BM

Analysis and interpretation: FS, HM, AD, HV, FM, BM

Data collection: FS, HM, BM

Writing the article: FS, HM, BM

Critical revision of the article: FS, HM, AD, HV, FM, BM

Final approval of the article: FS, HM, AD, HV, FM, BM

Statistical analysis: FS, HM, BM

Obtained funding: Not applicable

Overall responsibility: FS

Back to Article Outline

References 

  1. Ferro CR, de Oliveira DC, Guerra FF, de Lucena AJ, Nunes FP, Ortiz ST, et al. Prevalence and risk factors for combined coronary artery disease and aortic aneurysm. Arq Bras Cardiol. 2007;88:40–44
  2. Suzuki S, Davis CA, Miller CC, Huynh TT, Estrera AL, Porat EE, et al. Cardiac function predicts mortality following thoracoabdominal and descending thoracic aortic aneurysm repair. Eur J Cardiothorac Surg. 2003;24:119–124
  3. Kieffer E, Chiche L, Baron JF, Godet G, Koskas F, Bahnini A. Coronary and carotid artery disease in patients with degenerative aneurysm of the descending thoracic or thoracoabdominal aorta: prevalence and impact on operative mortality. Ann Vasc Surg. 2002;16:679–684
  4. Brooks MJ, Mayet J, Glenville B, Foale R, Wolfe JH. Cardiac investigation and intervention prior to thoraco-abdominal aneurysm repair: coronary angiography in 35 patients. Eur J Vasc Endovasc Surg. 2001;21:437–444
  5. Islamoglu F, Atay Y, Can L, Kara E, Ozbaran M, Yuksel M, et al. Diagnosis and treatment of concomitant aortic and coronary disease: a retrospective study and brief review. Tex Heart Inst J. 1999;26:182–188
  6. Olsson C, Eriksson N, Stahle E, Thelin S. Surgical and long-term mortality in 2634 consecutive patients operated on the proximal thoracic aorta. Eur J Cardiothorac Surg. 2007;31:963–969
  7. Ueda T, Shimizu H, Shin H, Kashima I, Tsutsumi K, Iino Y, et al. Detection and management of concomitant coronary artery disease in patients undergoing thoracic aortic surgery. Jpn J Thorac Cardiovasc Surg. 2001;49:424–430
  8. Zierer A, Melby SJ, Lubahn JG, Sicard GA, Damiano RJ, Moon MR. Elective surgery for thoracic aortic aneurysms: late functional status and quality of life. Ann Thorac Surg. 2006;82:573–578
  9. Rigberg DA, McGory ML, Zingmond DS, Maggard MA, Agustin M, Lawrence PF, et al. Thirty-day mortality statistics underestimate the risk of repair of thoracoabdominal aortic aneurysms: a statewide experience. J Vasc Surg. 2006;43:217–223
  10. Dowe DA. How to create a cardiac CT clinic. J Thorac Imaging. 2007;22:17–21
  11. Roos JE, Willmann JK, Weishaupt D, Lachat M, Marincek B, Hilfiker PR. Thoracic aorta: motion artifact reduction with retrospective and prospective electrocardiography-assisted multi-detector row CT. Radiology. 2002;222:271–277
  12. Teutelink A, Muhs BE, Vincken KL, Bartels LW, Cornelissen SA, van Herwaarden JA, et al. Use of dynamic computed tomography to evaluate pre- and postoperative aortic changes in AAA patients undergoing endovascular aneurysm repair. J Endovasc Surg. 2007;14:44–49
  13. Muhs BE, Vincken KL, van Prehn J, Stone MK, Bartels LW, Prokop M, et al. Dynamic cine-CT angiography for the evaluation of the thoracic aorta; insight in dynamic changes with implications for thoracic endograft treatment. Eur J Vasc Endovasc Surg. 2006;32:532–536
  14. Morgan-Hughes GJ, Roobottom CA, Marshal AJ. Electrocardiographic gated multislice computed tomography of the thoracic aorta. Heart. 2003;89:838
  15. Van Prehn J, Vincken KL, Muhs BE, Barwegen GK, Bartels LW, Prokop M, et al. Toward endografting of the ascending aorta: insight into dynamics using dynamic cine-CTA. J Endovasc Ther. 2007;14:551–560
  16. Manghat NE, Morgan-Hughes GJ, Roobottom CA. Multi-detector row computed tomography: imaging in acute aortic syndrome. Clin Radiol. 2005;60:1256–1267
  17. Agatston AS, Janowitz WR, Hildner FJ, Zusmer NR, Viamonte M, Detrano R. Quantification of coronary artery calcium using ultrafast computed tomography. J Am Coll Cardiol. 1990;15:827–832
  18. Maron MS, Zenovich AG, Casey SA, Link MS, Udelson JE, Aeppli DM, et al. Significance and relation between magnitude of left ventricular hypertrophy and heart failure symptoms in hypertrophic cardiomyopathy. Am J Cardiol. 2005;95:1329–1333
  19. Sweitzer NK, Lopatin M, Yancy CW, Mills RM, Stevenson LW. Comparison of clinical features and outcomes of patients hospitalized with heart failure and normal ejection fraction (>/=55%) versus those with mildly reduced (40% to 55%) and moderately to severely reduced (<40%) fractions. Am J Cardiol. 2008;101:1151–1156
  20. Raggi P, Callister TQ, Cooil B, He ZX, Lippolis NJ, Russo DJ, et al. Identification of patients at increased risk of first unheralded acute myocardial infarction by electron-beam computed tomography. Circulation. 2000;101:850–855
  21. Arad Y, Goodman KJ, Roth M, Newstein D, Guerci AD. Coronary calcification, coronary disease risk factors, C-reactive protein, and atherosclerotic cardiovascular disease events: the St. Francis Heart Study. J Am Coll Cardiol. 2005;46:158–165
  22. Herzog C, Zangos S, Zwerner P, Costello P, Vogl TJ, Schoepf UJ. CT of coronary artery disease. J Thorac Imaging. 2007;22:40–48
  23. Hong C, Bae KT, Pilgram TK. Coronary artery calcium: accuracy and reproducibility of measurements with multi-detector row CT–assessment of effects of different thresholds and quantification methods. Radiology. 2003;227:795–801
  24. Kerl JM, Hofmann LK, Thilo C, Vogl TJ, Costello P, Schoepf UJ. Coronary CTA: image acquisition and interpretation. J Thorac Imaging. 2007;22:22–34
  25. Chartrand-Lefebvre C, Cadrin-Chenevert A, Bordeleau E, Ugolini P, Ouellet R, Sablayrolles JL, et al. Coronary computed tomography angiography: overview of technical aspects, current concepts, and perspectives. Can Assoc Radiol J. 2007;58:92–108
  26. Delhaye D, Remy-Jardin M, Rozel C, Dusson C, Wurtz A, Delannoy-Deken V, et al. Coronary artery imaging during preoperative CT staging: preliminary experience with 64-slice multidetector CT in 99 consecutive patients. Eur Radiol. 2007;17:591–602
  27. Kim SY, Seo JB, Do KH, Heo JN, Lee JS, Song JW, et al. Coronary artery anomalies: classification and ECG-gated multi-detector row CT findings with angiographic correlation. Radiographics. 2006;26:317–333
  28. Fallenberg M, Juergens KU, Wichter T, Scheld HH, Fischbach R. Coronary artery aneurysm and type-A aortic dissection demonstrated by retrospectively ECG-gated multislice spiral CT. Eur Radiol. 2002;12:201–204
  29. Salm LP, Bax JJ, Jukema JW, Schuijf JD, Vliegen HW, Lamb HJ, et al. Comprehensive assessment of patients after coronary artery bypass grafting by 16-detector-row computed tomography. Am Heart J. 2005;150:775–781
  30. Remy-Jardin M, Delhaye D, Teisseire A, Hossein-Foucher C, Duhamel A, Remy J. MDCT of right ventricular function: impact of methodologic approach in estimation of right ventricular ejection fraction, part 2. AJR Am J Roentgenol. 2006;187:1605–1609
  31. Schepis T, Gaemperli O, Koepfli P, Valenta I, Strobel K, Brunner A, et al. Comparison of 64-slice CT with gated SPECT for evaluation of left ventricular function. J Nucl Med. 2006;47:1288–1294
  32. Salem R, Remy-Jardin M, Delhaye D, Khalil C, Teisseire A, Delannoy-Deken V, et al. Integrated cardio-thoracic imaging with ECG-Gated 64-slice multidetector-row CT: initial findings in 133 patients. Eur Radiol. 2006;16:1973–1981
  33. Yamamuro M, Tadamura E, Kubo S, Toyoda H, Nishina T, Ohba M, et al. Cardiac functional analysis with multi-detector row CT and segmental reconstruction algorithm: comparison with echocardiography, SPECT, and MR imaging. Radiology. 2005;234:381–390
  34. Pannu HK, Jacobs JE, Lai S, Fishman EK. Gated cardiac imaging of the aortic valve on 64-slice multidetector row computed tomography: preliminary observations. J Comput Assist Tomogr. 2006;30:443–446
  35. Alkadhi H, Bettex D, Wildermuth S, Baumert B, Plass A, Grunenfelder J, et al. Dynamic cine imaging of the mitral valve with 16-MDCT: a feasibility study. AJR Am J Roentgenol. 2005;185:636–646
  36. Sosnouski D, Bonsall RP, Mayer FB, Ravenel JG. Extracardiac findings at cardiac CT: a practical approach. J Thorac Imaging. 2007;22:77–85
  37. Raptopoulos VD, Boiselle PB, Michailidis N, Handwerker J, Sabir A, Edlow JA, et al. MDCT angiography of acute chest pain: evaluation of ECG-gated and nongated techniques. AJR Am J Roentgenol. 2006;186:S346–S356
  38. Zanzonico P, Rothenberg LN, Strauss HW. Radiation exposure of computed tomography and direct intracoronary angiography: risk has its reward. J Am Coll Cardiol. 2006;47:1846–1849
  39. Schoepf UJ, Becker CR, Ohnesorge BM, Yucel EK. CT of coronary artery disease. Radiology. 2004;232:18–37
  40. Jakobs TF, Becker CR, Ohnesorge B, Flohr T, Suess C, Schoepf UJ, et al. Multislice helical CT of the heart with retrospective ECG gating: reduction of radiation exposure by ECG-controlled tube current modulation. Eur Radiol. 2002;12:1081–1086
  41. Earls JP, Berman EL, Urban BA, Curry CA, Lane JL, Jennings RS, et al. Prospectively gated transverse coronary CT angiography versus retrospectively gated helical technique: improved image quality and reduced radiation dose. Radiology. 2008;246:742–753
  42. Hausleiter J, Meyer T, Hadamitzky M, Huber E, Zankl M, Martinoff S, et al. Radiation dose estimates from cardiac multislice computed tomography in daily practice: impact of different scanning protocols on effective dose estimates. Circulation. 2006;113:1305–1310
  43. Hoffmann MH, Shi H, Manzke R, Schmid FT, De Vries L, Grass M, et al. Noninvasive coronary angiography with 16-detector row CT: effect of heart rate. Radiology. 2005;234:86–97
  44. Leber AW, Knez A, von Ziegler F, Becker A, Nikolaou K, Paul S, et al. Quantification of obstructive and nonobstructive coronary lesions by 64-slice computed tomography. J Am Coll Cardiol. 2005;46:147–154
  45. Fine JJ, Hopkins CB, Ruff N, Newton FC. Comparison of accuracy of 64-slice cardiovascular computed tomography with coronary angiography in patients with suspected coronary artery disease. Am J Cardiol. 2006;97:173–174
  46. Kramer CM. All high-risk patients should not be screened with computed tomographic angiography. Circulation. 2008;117:1333–1339
  47. Gottlieb I, Lima JA. Screening high-risk patients with computed tomography angiography. Circulation. 2008;117:1318–1332

 Competition of interest: none.

PII: S0741-5214(08)00699-X

doi:10.1016/j.jvs.2008.04.055

Journal of Vascular Surgery
Volume 48, Issue 3 , Pages 561-570, September 2008

Article Tools

* Image Usage & Resolution