Interventional Cardiology
Table 1: Relative Advantages and Disadvantages of Echocardiographic Imaging Modalities
Advantages TTE
Accessible, widely available, portable, safe
Excellent image quality Broad range of clinical applications
Doppler and 3D capability TEE
Superior image quality to TTE Broad range of clinical applications
Doppler and 3D capability Rapid visualisation and spatial orientation, improved visualisation of wires and catheters, more intuitive
image display (3D) Serious complications rare
ICE
Single operator use General anaesthesia not required
Good visualisation of inferior atrial septum
Alternative imaging technique
Narrower range of clinical applications than TTE/TEE
Expensive, single-use catheters No 3D capability Catheter instability
Potential risks such as vascular
in those with contraindications to complications, cardiac TEE, e.g. oesophageal pathology perforation, arrhythmias and thromboembolism
ICE = intra-cardiac echocardiography; TEE = transoesophageal echocardiography; TTE = transthoracic echocardiography.
relative advantages and disadvantages compared with the others (see Table 1). Therefore, selection of the optimal imaging modality for any given interventional cardiac procedure must take into account both the specific requirements of the procedure and the relative strengths and weaknesses of the imaging modality to ensure the greatest likelihood of successful outcome.
Congenital and Acquired Septal Defects Percutaneous Atrial Septal Defect/ Patent Foramen Ovale Device Closure
Percutaneous device closure is increasingly the therapy of choice for patients with atrial septal defect (ASD) or patent foramen ovale (PFO), where clinically appropriate and in the absence of complicated cardiac anatomy or other indications for cardiac surgery.1,2
It improves functional status in symptomatic patients and exercise capacity in both asymptomatic and symptomatic patients, although long-term follow-up safety and efficacy data are awaited.4,5
In experienced hands, it is a safe and effective procedure with a risk of serious complications, such as device embolisation, of less than 1%.3
Echocardiography plays a key role before, during and after percutaneous ASD/PFO device closure. Indeed, its use for procedural guidance, in addition to primary fluoroscopy, was recently recommended by the American Society of Echocardiography (ASE).6 Typically, the diagnosis of an inter-atrial shunt is made by TTE with colour Doppler and/or agitated saline or gelofusin contrast injection.
72 General anaesthesia
(except for nasal TEE) and additional operator required Additional training required (2D and 3D)
Decreased temporal resolution tissue dropout, artefacts (3D) Recognised contraindications
Limited visualisation of some cardiac structures and intra-cardiac devices
Possible interference with execution of interventional procedure
Disadvantages
TTE also provides information about the type of defect, its haemodynamic significance and any associated anomalies. However, if percutaneous closure is clinically indicated, detailed assessment of the inter-atrial septal anatomy and surrounding structures is required by either TEE or ICE.
Systematic evaluation of the inter-atrial septum and surrounding structures should be performed to determine defect type, size and PFO tunnel length, the presence of fenestrations, aneurysmal septum or prominent Eustachian valve or Chiari network, and to exclude associated abnormality of the inferior and superior vena cavae, pulmonary veins, coronary sinus and atrioventricular valves. Furthermore, consideration of the size of the defect rims and total atrial septal length are important in determining the likelihood of procedural success.7,8
This evaluation enables the interventional
cardiologist to plan the procedure and to choose from a variety of ASD and PFO closure devices with differing designs and characteristics. Currently, only isolated ostium secundum type ASDs and PFOs are suitable for device closure. Possible contraindications to device closure identified by echocardiography therefore include very large (>38mm) or multiple defects, deficient (1/3) rims, close proximity of the defect to the atrioventricular valves, sinus venosus defects, anomalous pulmonary venous drainage, ASD with severe pulmonary hypertension and bi-directional or right-to-left shunting and intra- cardiac thrombus. Intra-procedural imaging (TEE or ICE) facilitates wire and catheter manipulation and positioning, balloon sizing of the defect and device deployment, as well as enabling pre- and post-closure assessment of adjacent cardiac structures and early identification of complications such as pericardial effusion.9–13 Following device closure, TTE is indicated at routine intervals to confirm device stability, evaluate the presence of any residual shunt and detect the development of late complications.11,14,15
The advent of realtime 3D TEE has enhanced the evaluation of ASDs. 2D echocardiography may underestimate both the size and complexity of an ASD; however, 3D echocardiography clearly defines inter-atrial septal anatomy and enables an en face view of the defect (see Figure 1A).16–18
Multiplanar reconstruction of the 3D data set
allows accurate measurement of the minimum and maximum dimensions of the defect, facilitating selection of the optimal size and type of closure device (see Figure 1B).19
Moreover, intra-
procedural realtime 3D TEE, in addition to 2D, provides superior visualisation of wires, catheters and devices and their relationships to neighbouring structures in a format that is generally more intuitively comprehended by the interventional cardiologist (see Figures 1C and 1D). The advantages of realtime 3D TEE in guiding cardiac catheter interventions are increasingly recognised.20,21
ICE is also commonly used to guide ASD/PFO device closure in many centres. It provides comparable imaging of the inter-atrial septum and surrounding structures to 2D TEE, and indeed may enable superior visualisation of the inferoposterior inter-atrial septum.11,12,22 However, it also has the distinct advantages of requiring neither general anaesthesia nor additional echocardiographic support, as it may be performed by the primary operator. As such, ICE has been shown to reduce fluoroscopy and procedure times, as well as offering comparable cost to procedures performed under general anaesthesia with TEE guidance.9,10,22,23
However, potential disadvantages of ICE include limited far-field view, lack of catheter stability, the expense of EUROPEAN CARDIOLOGY
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