Role of Imaging in Interventions on Structural Heart Disease
Atrial septal defects (ASDs) are the second most common type of congenital heart disease. The most frequent variant of ASD, the ostium secundum (OS) type, results from deficiency of the flap valve of the oval fossa, ranging from incomplete development, with failed overlapping to the septum secundum, to the presence of multiple fenestrations, to complete absence.
Transcatheter closure of ASD has been practiced for over 30 years and is now established as the standard technique for definitive treatment of ASDs of the OS type. It is unfeasible for the other variants of ASD, for example, the sinus venosus or ostium primum types. To be eligible for transcatheter implantation of an occluding device, an ASD must meet certain criteria, concerning size, margins and proximity to other structures.
Although fluoroscopy guidance is generally considered as mandatory in transcatheter interventions, echocardiography plays an essential role both in pre-procedural assessment and intraprocedural guidance of percutaneous closure of ASD. Transthoracic echocardiography (TTE) provides valuable information in most patients, and is the most widely used imaging tool for evaluation of size and hemodynamic significance of the defects and for decision-making. However, in some children and many adults with poor acoustic windows, the amount of information provided can be limited.
Transesophageal echocardiography (TEE) is widely established as a fundamental imaging modality for guidance of percutaneous closure of septal defects: coupled with fluoroscopy, it provides detailed and reliable information in real time to the operator, enabling measurement of the defects and of their rims, visualization of devices during deployment and release and evaluation of the results (Figures 1 & 2). There are miniaturized probes available, which are suitable for infants and children with weights as low as 4 kg. All commercially available probes can provide multi-planar imaging. In most institutions children, and often adults, needing TEE for transcatheter intervention undergo general anesthesia during the procedure, to secure the airways and avoid distress. Conventional two-dimensional TEE (2DTEE) has however some intrinsic limitations. Obtaining detailed information such as number, size, shape and spatial relationships of multiple or multifenestrated ASDs can often be challenging with two-dimensional imaging. 2DTEE guidance is also significantly limited in locating guidewires and catheters and assessing device position, particularly when multiple devices are used.
(Enlarge Image)
Figure 1.
2DTEE view of a moderate-sized atrial septal defect ostium secundum in the bicaval projection. The color flow map clearly shows the left to right shunt across the defect.
(Enlarge Image)
Figure 2.
2DTEE view of the atrial septum after implantation of Amplatzer Septal Occluder device.
Real-time three-dimensional transesophageal echocardiography (RT3DTEE) is a recent innovation in echocardiographic imaging, based on miniaturized matrix array transducers, that allows three-dimensional imaging in real time without the need for multiple-beat acquisition and is particularly useful for guidance of percutaneous procedures. As reported in many series, RT3DTEE enables accurate localization of guidewires and catheters when crossing the defects, and monitoring of device deployment and release (Figures 3 & 4). In cases where multiple devices are used, RT3DTEE provides information on their arrangement and relationship with surrounding structures (Figures 5 & 6).
(Enlarge Image)
Figure 3.
RT3DTEE view of the atrial septum from the left atrial side. A catheter (arrow) is seen crossing the atrial septal defect.
(Enlarge Image)
Figure 4.
RT3DTEE view of a device from the left atrial side, after deployment of the distal disk. The proximal disk is still contained in the delivery sheath.
(Enlarge Image)
Figure 5.
RT3DTEE view of a double atrial septal defect, from the right atrial side. Both defects are crossed by catheters (arrows).
(Enlarge Image)
Figure 6.
Two devices have been implanted in two separate atrial septal defects; RT3DTEE confirms their correct placement, with partial overlapping.
Intracardiac echocardiography (ICE) is becoming one of the most widely used ultrasound-based imaging tools to guide device closure of ASDs and patent foramen ovale (PFO). Imaging with ICE has evolved from cross-sectional imaging using a rotating transducer, useful for near field imaging, to sector-based imaging using a phased array transducer, useful for far field imaging.
Atrial Septal Defect
Atrial septal defects (ASDs) are the second most common type of congenital heart disease. The most frequent variant of ASD, the ostium secundum (OS) type, results from deficiency of the flap valve of the oval fossa, ranging from incomplete development, with failed overlapping to the septum secundum, to the presence of multiple fenestrations, to complete absence.
Transcatheter closure of ASD has been practiced for over 30 years and is now established as the standard technique for definitive treatment of ASDs of the OS type. It is unfeasible for the other variants of ASD, for example, the sinus venosus or ostium primum types. To be eligible for transcatheter implantation of an occluding device, an ASD must meet certain criteria, concerning size, margins and proximity to other structures.
Although fluoroscopy guidance is generally considered as mandatory in transcatheter interventions, echocardiography plays an essential role both in pre-procedural assessment and intraprocedural guidance of percutaneous closure of ASD. Transthoracic echocardiography (TTE) provides valuable information in most patients, and is the most widely used imaging tool for evaluation of size and hemodynamic significance of the defects and for decision-making. However, in some children and many adults with poor acoustic windows, the amount of information provided can be limited.
Transesophageal echocardiography (TEE) is widely established as a fundamental imaging modality for guidance of percutaneous closure of septal defects: coupled with fluoroscopy, it provides detailed and reliable information in real time to the operator, enabling measurement of the defects and of their rims, visualization of devices during deployment and release and evaluation of the results (Figures 1 & 2). There are miniaturized probes available, which are suitable for infants and children with weights as low as 4 kg. All commercially available probes can provide multi-planar imaging. In most institutions children, and often adults, needing TEE for transcatheter intervention undergo general anesthesia during the procedure, to secure the airways and avoid distress. Conventional two-dimensional TEE (2DTEE) has however some intrinsic limitations. Obtaining detailed information such as number, size, shape and spatial relationships of multiple or multifenestrated ASDs can often be challenging with two-dimensional imaging. 2DTEE guidance is also significantly limited in locating guidewires and catheters and assessing device position, particularly when multiple devices are used.
(Enlarge Image)
Figure 1.
2DTEE view of a moderate-sized atrial septal defect ostium secundum in the bicaval projection. The color flow map clearly shows the left to right shunt across the defect.
(Enlarge Image)
Figure 2.
2DTEE view of the atrial septum after implantation of Amplatzer Septal Occluder device.
Real-time three-dimensional transesophageal echocardiography (RT3DTEE) is a recent innovation in echocardiographic imaging, based on miniaturized matrix array transducers, that allows three-dimensional imaging in real time without the need for multiple-beat acquisition and is particularly useful for guidance of percutaneous procedures. As reported in many series, RT3DTEE enables accurate localization of guidewires and catheters when crossing the defects, and monitoring of device deployment and release (Figures 3 & 4). In cases where multiple devices are used, RT3DTEE provides information on their arrangement and relationship with surrounding structures (Figures 5 & 6).
(Enlarge Image)
Figure 3.
RT3DTEE view of the atrial septum from the left atrial side. A catheter (arrow) is seen crossing the atrial septal defect.
(Enlarge Image)
Figure 4.
RT3DTEE view of a device from the left atrial side, after deployment of the distal disk. The proximal disk is still contained in the delivery sheath.
(Enlarge Image)
Figure 5.
RT3DTEE view of a double atrial septal defect, from the right atrial side. Both defects are crossed by catheters (arrows).
(Enlarge Image)
Figure 6.
Two devices have been implanted in two separate atrial septal defects; RT3DTEE confirms their correct placement, with partial overlapping.
Intracardiac echocardiography (ICE) is becoming one of the most widely used ultrasound-based imaging tools to guide device closure of ASDs and patent foramen ovale (PFO). Imaging with ICE has evolved from cross-sectional imaging using a rotating transducer, useful for near field imaging, to sector-based imaging using a phased array transducer, useful for far field imaging.
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