Multidetector computed tomography in the evaluation of atrial septal defects

Transcription

1 Multidetector computed tomography in the evaluation of atrial septal defects Poster No.: C-0502 Congress: ECR 2010 Type: Educational Exhibit Topic: Cardiac Authors: S. Espejo, R. Ysamat, B. Cajal, M. Pan, M. Romero, D. Garcia, D. Mesa, J. Suarez de Lezo; Córdoba/ES Keywords: Computed Tomography, Atrial septal defect, Septal rims DOI: /ecr2010/C-0502 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 19

2 Learning objectives To describe a new Multidetector Computed Tomography (MDCT) protocol in the evaluation of atrial septal defects (ASD). Fig.: Atrial septal defect. A) Echocardiography (four chamber view). B) Computed Tomography (axial plane). White and black arrows indicate the ASD. Coloured image of ASD is from ( 2009 NMT Medical, Inc) References: S. Espejo; Radiology, Hospital Universitario Reina Sofía, Córdoba, SPAIN Images for this section: Page 2 of 19

3 Fig. 1: Atrial septal defect. A) Echocardiography (four chamber view). B) Computed Tomography (axial plane). White and black arrows indicate the ASD. Coloured image of ASD is from ( 2009 NMT Medical, Inc) Page 3 of 19

4 Background Percutaneous closure of atrial septal defects (ASD) is a safe and effective alternative to surgical closure that has gained acceptance in recent years. However, implantation failure and device embolization may occur despite experienced operators [1,2]. For successful of the procedure, it is important for the interventional cardiologist to have an accurate information of the anatomy of the defect. Knowledge of the morphology and maximal diameter of the defect, as well as precise information of the circumferential rims and the structures that surround the ASD are required. For this purpose, Amin et al [1], proposed a classification of the atrial septal rims on page 4 based upon the adjacent structures. Thus, he defined six atrial rims: aortic rim, the atrial septal rim that is adjacent to the aortic valve; superior vena cava (SVC) rim, the rim that is adyacent to the SVC; superior rim, the rim that is between the SVC rim and the aortic rim; posterior rim, the rim that is opposite to the aortic rim; inferior vena cava (IVC) rim, the rim adjacent to the IVC; atrio-ventricular valve (AV) rim, the rim that is adjacent to the AV valve rim. All those structures are usually evaluated by Transesophageal Echocardiography (TEE). This imaging modality plays an important role in the selection of patients and as an imaging toolguiding device deployment [1,3]. Complete echocardiographic examination of the ASD includes measurement of the defect and measurement of the septal rims in three standard views on page 5 [1] that are utilized during the percutaneous closure procedure. These views are: 1) the aortic short axis view, to evaluate the aortic rim and the posterior rim; 2) the bicaval view, in which the SVC and IVC rims can be evaluated; and 3) the four-chambers view, to evaluate the AV valve rim and the superior rim. Although TEE is a valuable tool, sometimes it has technical limitations in the visualization of the entire atrial septum as well as in the evaluation of the maximal defect diameter. Images for this section: Page 4 of 19

5 Fig. 1: Classification of septal rims by Amin. Modified from Amin(2006) Transcatheter closure of secundum atrial septal defects. Catheter Cardiovasc Interv 68: SVC (superior vena cava); IVC (inferior vena cava); Ao (aorta), TV (tricuspid valve). Page 5 of 19

6 Fig. 2: Amin s atrial septal rims classification with TEE. A) Four-chamber view: superior rim (SUP) and AV-valve rim (AV). B) Bi-caval view: Inferior vena cava rim (IVC) and superior vena cava rim (SVC). Blue arrow indicates de SVC. C) Aortic short axis view: posterior rim (P) and aortic rim (A). Aortic valve plane (red arrowhead). LA (left atrium); RA (right atrium). Page 6 of 19

7 Imaging findings OR Procedure details With the evolution of ever faster and more sophisticated MDCT technologies, CT of the heart has evolved into an examination that is applied in a variety of clinical situations. Electrocardiogram-gated cardiac CT allows the acquisition of detailed images of the heart to be taken without cardiac pulsation. Atrial septum and its abnormalities can be evaluated [4,5]. High quality images of the entire atrial septum in the same views as in the TEE on page 9, permit exact measurements of the septal defect and of the rims. This CT examination is performed in patients with known atrial septal defect. CT scan protocol Cardiac CT is performed using a 64-slice scanner. To reduce radiation exposition, a prospective acquisition of the images is performed (effective radiation dose (msv): 4.33±1.37) -Patient preparation: Slow heart rates are desirable for cardiac CT (between 50 to 65 beats per minute). Before the scan, oral #-blocker are used to achieve a heart rate of less than 65 bpm. Patient is positioned in the supine, feet-first position in the gantry scanner. A three lead-ecg is used for the ECG gaiting. - Contrast administration: Intravenous access is preferably established in the right cubital vein, using an 18 or 20-gauge catheter. With respect to IV contrast administration, a triphasic technique is used as follows: 75ml of no-ionic contrast material (370mg I/mL of iodine concentration) injected at 4-5ml/sec, followed by a mixture of saline and contrast material (30ml) injected at 3ml/sec, and followed by a saline bolus (20mL) injected at 2ml/sec. This examination is also performed in children older than six years: in this case the injection access route usually necessitates a lower flow rate, around ml/sec. - Scan protocol: To trigger the start of the scan, a real-time bolus tracking technique is used. The scan parameters are: detector collimation: 64x0.6mm; scanner rotation time: 0.35s; tube voltaje: Kv; tube current mA (in children 100Kw; mA). Image reconstruction protocol Page 7 of 19

8 All data are transferred to a three-dimensional workstation. Reformations of the images with respect the principal axes of the body (axial, sagittal and coronal) are rendered. To obtain the same views as in TEE (aortic short axis view, bi-caval view and four-chamber view), oblique planes are performed as follows: - Aortic short axis view on page 9: From a coronal image at the level of the aortic valve, a parallel line to the aortic valve plane is drawn (Fig ). The obtained plane at this level, shows the aortic valve leaflets and the retroaortic atrial septum. Around 40 to 50 images parallel to this plane, are rendered covering the entire atrial septum ( images are reconstructed at 1mm slice thickness with 1mm interval). The image showing the maximal ASD diameter and the minimal rims length is selected for the measurements. - Bi-caval view on page 10: From an axial image at the level of both AV valves, a line is drawn perpendicular to the atrial septum. The obtained plane reproduces the bi-caval TEE view. Other 40 to 50 images of the entire atrial septum are rendered parallel to this plane. The SVC and IVC rims can be measurred in this view. The image showing the maximal ASD diameter and the minimal rims length is selected for the measurements. - Four-chamber view: on page 11 From a sagittal image at the level of the mitral valve a line is drawn through the apex to the middle of mitral leaflets. The obtained plane shows the four chamber view. The entire septum is also studied with the same protocol as in the other views. The AV and superior rims can be clearly measured. Measurements and imaging findings Measurements on page 12 performed in each view are: 1.-The total atrial septal length. 2.- The maximal ASD diameter. 3.- The minimal rims length. These measurements are crucial in the decision of closure treatment (percutaneous or surgical closure). In case of percutaneous treatment they are used to determine the size of the devide. In case of large ASD on page 13 and deficient rims, surgical closure is preferable. Page 8 of 19

9 In some cases there are two or more holes on page 14 (known as cribiform ASD). CT permits the detection of multiple holes. Cardiac or extracardiac anomalies related to ASD may also be detected in CT study (for example, anomalous pulmonary vein drainage on page 15). Other cardiac structures such as coronary arteries on page 16, cardiac chambers, valves and pericardium, can be assessed. Images for this section: Fig. 1: Atrial septal rims in the three standard views. TEE and CT correlation. Page 9 of 19

10 Fig. 2: Aortic short axis view. a) Coronal plane at the level of the aortic valve. A parallel line to the aortic valve plane is drawn. b) The plane obtained is the aortic short axis view. In this view, the aortic valve leaflets (*) and the retroaortic atrial septum are shown. The aortic (A) and posterior (P) rims cam be measured. c) Around 40 to 50 images parallel to this plane, are rendered covering the entire atrial septum (selected images are shown). The image showing the maximal ASD diameter and the minimal rims length are selected for the measurements (the biggest image). Page 10 of 19

11 Fig. 3: Bi-caval view. a) Axial plane at the level of both AV valves. A line is drawn perpendicular to the atrial septum. b) The obtained plane reproduces the bi-caval TEE view (in this case, the SVC rim is good in thickness and length, but the IVC rim is very thin). c) Other 40 to 50 images of the entire atrial septum are rendered parallel to this plane (selected images are shown). SVC and IVC rims can be measured in the less favourable image (the biggest image). Page 11 of 19

12 Fig. 4: Four-chamber view. a) Sagittal plane at the level of the mitral valve (M: mitral valve). A line is drawn through the apex to the middle of mitral leaflets. b) The fourchamber view is obtained. c) The entire septum is studied with the same protocol described in the other views. The AV and superior rims can be clearly measured. In this case a septal aneurysm is present (part of the atrial septum is very thin and protrudes in the right atrium). Page 12 of 19

13 Fig. 5: Measurements. In each view, the total atrial septal length, the maximal ASD diameter and the minimal rims length are measured. In this case, de aortic rim in the aortic short axis view is absent. Page 13 of 19

14 Fig. 6: Large ASD. Nine year-old girl with ASD. A) Four-chamber view: AV and superior rims are short. Right cardiac chambers are dilated due to the ASD. B) Bi-caval view: the VCS rim is short. The IVC is long but very thin. C) Aortic short axis view: the posterior rim is very short and the aortic rim is absent. Due to the scarcity of rims and the size of the ASD, patient underwent surgery. Page 14 of 19

15 Fig. 7: ASD with two holes. Four-chamber, aortic short axis and bi-caval views showing two holes in the atrial septum [hole 1 (one arrow) and hole 2 (two arrows)]. Two devices were implanted in the percutaneous procedure. Page 15 of 19

16 Fig. 8: ASD associated with partial anomalous pulmonary venous drainage (PAPVD). The ASD (black arrow) is shown in the axial (A) and four-chamber view (B). C) MIP images in axial, coronal and oblique planes, show the PAPVD: the superior right pulmonary vein (green point) drains in the SVC (red asterisk). Page 16 of 19

17 Fig. 9: ASD associated with coronary artery disease. Four-chamber, aortic short axis and bi-caval views showing an ASD. A contrast media yet from the left atrium to the right atrium is shown. Proximal Left anterior descending artery with significant lesion. Page 17 of 19

18 Conclusion - Cardiac CT enables a comprehensive evaluation of ASD. High quality images of the total atrial septum in the same views as in TEE, permit exact measurements of the defect and of the septal rims. - This technique also allows the detection and evaluation of other cardiac or extracardiac findings, related or not related to ASD. - Multiplanar CT evaluation of the atrial septum allows an accurate selection of occluder diameter and avoids the use of ballon sizing techniques and additional angiograms, simplifying the procedure. Personal Information Simona Espejo Pérez Servicio de Radiología Hospital Universitario Reina Sofía Códoba, SPAIN simonaep@gmail.com References 1.- Amin Z. Transcatheter closure of secundum atrial septal defects. Catheter and cardiovasc interv 2006;68: Amin Z, Hijazi ZM, Bass JL, Cheatham JP, Hellenbrand W, Kleinman C. Erosion of Amplatzer septal occluder device after closure of atrial septal defects: Review of registry of complications and recommendations to minimize future risk. Catheter Cardiovasc Interv 2004;63: Page 18 of 19

19 3.- Graham R, Gelman J. Echocardiographic aspects of percutaneous atrial septal defect closure in adults. Heart, Lung and Circulation 2001;10: Kin YJ, Hur J, Choe KO et al. Interatrial shunt detected in coronary computed tomography angiography: differential features of a patent foramen ovale and an atrial septal defec. J Comput Assist Tomogr 2008;32(5): Hoey ET, Gopalan D, Ganesh V. Atrial septal defects: magnetic resonance and computed tomography appearances. J Med Imaging Radiat Oncol 2009;53: Page 19 of 19