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Intraoperative Three-Dimensional Echocardiography: Ready for PrimeTime?

2009; Elsevier BV; Volume: 22; Issue: 1 Linguagem: Inglês

10.1016/j.echo.2008.11.012

1097-6795

Stanton K. Shernan,

Cardiac and Coronary Surgery Techniques

Over the past 30 years, technological advances have significantly contributed to the development of perioperative echocardiography as an invaluable diagnostic tool and monitor of cardiac performance for the management of cardiac surgical patients. Intraoperative echocardiography was first introduced into clinical practice in the early 1970s for the evaluation of open mitral valve commisurotomy, using M-mode ultrasound via an epicardial approach with conventional transthoracic echocardiographic probes enclosed in sterile sheaths. The introduction of intraoperative transesophageal echocardiography (TEE) in the early 1980s provided the catalyst for subsequent innovative developments. Consequently, modern day echocardiography probes and consoles that are currently capable of producing high resolution, multi-plane two-dimensional (2D) images of cardiovascular anatomy and permitting accurate, noninvasive quantification of blood flow have made significant contributions to perioperative clinical decision-making and outcomes. Although the concept of three-dimensional (3D) echocardiography was first introduced in the early 1970s, its utility in the perioperative environment has only recently acquired appropriate recognition. Advantages of both conventional 3D reconstruction and real-time 3D imaging techniques for enhancing the diagnostic confidence of conventional echocardiography in the perioperative period have begun to emerge in the literature. Primary areas of interest have included the utility of 3D echocardiography in preoperative surgical planning, intraoperative assessment of the surgical procedure, and postoperative early and long-term follow up to determine the need for further intervention. Intraoperative 3D TEE may offer some primary advantages over 2D echocardiography. Three-dimensional echocardiography can provide a potentially more efficient process for acquiring a comprehensive echocardiographic examination, which may be particularly important in the volatile intraoperative environment where timely and effective clinically relevant decision-making may be critical. By enabling the inclusion of depth and volume, more data is available for interpretation in a given imaging window for evaluating global and regional ventricular function. For example, in contrast to conventional 2D echocardiographic imaging, 3D echocardiography may be more accurate for quantifying ventricular volumes in patients with severe ischemic cardiomyopathy, especially in the presence of significant geometric changes due to a ventricular aneurysm. Three-dimensional echocardiography may also be superior to 2D techniques for defining important geometric relationships between components of complex intracardiac structures such as the mitral apparatus. Furthermore, the ability to rotate and crop whole volume data sets without any directional restriction, enables an infinite number viewing perspectives of cardiac and great vessel infrastructure. In addition to enabling potentially greater efficiency in performing a comprehensive intraoperative TEE examination, 3D TEE may also permit more accurate diagnoses and more effective communication with interventionalists. Unique imaging windows of the mitral and tricuspid valve, as well as the left atrial appendage, which are not readily obtainable with 2D can be presented in en-face views to better appreciate anatomy and functional geometry, and help communicate relevant diagnostic information to those less familiar with echocardiographic displays. These unique views may be more familiar to cardiac surgeons and cardiology interventionalists, and may therefore facilitate a better understanding of abnormal anatomy and associated pathology. For example, 3D echocardiography enables accurate location and measurement of atrial septal defect dimensions in order to appropriately size closure devices and guide catheter based closure techniques. In addition, the ability to use 3D TEE to diagnose complex congenital heart lesions and valve abnormalities including mitral valve clefts and commissural lesions which often co-exist with more commonly encountered pathology (i.e., flail posterior leaflets), may enable more effective surgical planning since some of these findings are often subtle and difficult to appreciate in the unloaded heart during cardiopulmonary bypass. Furthermore, accurately identifying the specific location and severity of valvular regurgitant jets especially immediately following valve repair or replacement can also facilitate decision-making regarding the need for urgent further intervention. Finally, 3D echocardiography can also assist in determining mechanisms and severity of dynamic pathophysiological states which often require surgical intervention including functional mitral regurgitation, hypertrophic obstructive cardiomyopathy and systolic anterior motion of the mitral valve. There is considerable enthusiasm pertaining to the current utility of 3D TEE technology and its potential favorable impact on perioperative decision-making; however certain current limitations are worth noting. For example, while 3D reconstruction software and hardware using standard 2D, phased array multi-plane probes has been commercially available for over 10 years, this technology still relies on stable cardiac rhythms, respiratory and ECG gating, and both time and expertise for full volume acquisition reconstruction and "editing", which together may impose practical challenges in the operating room environment when attempting to efficiently obtain quality images worthy of interpretation. Three-dimensional TEE using miniaturized matrix arrays have been introduced more recently, and permit the acquisition of true "real-time" full volumes. However, some spatial and temporal resolution limitations, and the current need for hybrid reconstruction to incorporate full volume 3D color flow Doppler images, should be considered when comparing this advanced technology to "time-tested" 2D echocardiographic platforms. In addition, both reconstruction and real-time 3D TEE techniques still require a reasonable time commitment to learn how to acquire, manipulate, qualitatively interpret, and quantitatively analyze full volume echocardiographic images and data sets. Nonetheless, intraoperative 3D echocardiography is likely here to stay. Assuming continued exponential growth in the technological development of more sophisticated ultrasound transducers, the introduction of improvements in image acquisition, processing speed, real-time volume rendering with superimposed color flow doppler and transducer miniaturization, it is likely that future developments in 3D echocardiography may even permit the construction of individualized prosthetics and the creation of virtual surgical platforms. While the direct impact of 3D TEE on surgical outcomes has yet to be determined, perioperative 3D echocardiography will undoubtedly continue to improve upon the efficiency, accuracy, and communication of important diagnoses related to cardiovascular disease thereby facilitating clinical decision-making.