Three dimensional echocardiography: approaches and clinical utility

Effective performance and interpretation of two dimensional (2D) echocardiography requires one to mentally integrate the collected images into a three dimensional (3D) reconstruction of the heart. For example, prolapse of the mitral leaflets may involve the entire leaflet, or only a leaflet portion, requiring the echocardiographer to examine each individual leaflet portion from a series of 2D images and then to mentally ‘map’ the valve to define the location and nature of the abnormality. To do this accurately, one must understand the relationship of each 2D image to one another. Quantification of cardiac structure and function by 2D echocardiography typically requires assumptions about the geometry of the structure being measured so that specific formulae can be accurately used. The shapes of these structures may become altered in various diseases and thus the geometric assumptions about shape become less accurate as do the values calculated from the formulae. 3D echocardiography eliminates the need for cognitive reconstruction of image planes and use of geometric assumptions about shape of structures for cardiac quantitation. This particularly applies to complex shapes such as the right ventricle, an aneurysmal left ventricle (LV), an asymmetrically stenotic or regurgitant valve orifice, eccentric regurgitant jets assessed by colour Doppler, valve annulae, and the complex structural relationships observed in congenital heart lesions. 3D echocardiography can be performed from the transthoracic or transoesophageal approach. The 3D echocardiographic technique has the potential to decrease the time required for complete image acquisition of the heart. Also, the 3D echocardiogram can be viewed from various projections by rotation of the images resulting in an improved appreciation of the relationships between various cardiac structures. Up until recently, 3D echocardiography was primarily a research tool because off-line image reconstruction from a series of component 2D images was required (reconstruction technique) and this was very time consuming. …