|
|
NewsletterNew Guidelines and Nomenclature for TEE Why they were necessary Recently, new guidelines for performing a comprehensive TEE examination were endorsed by the American Society of Echocardiography (ASE) and the Society of Cardiovascular Anesthesiologists (SCA) and subsequently published in the Journal of the American Society of Echocardiography and Anesthesia and Analgesia.1,2 Members of the committee that developed these guidelines would like to explain to the SCA membership the reasons for creating these guidelines for a standardized comprehensive multiplane transesophageal (TEE) examination, the process used to develop, write, and endorse these guidelines, and how these guidelines can be used in clinical practice, education, and research. Reasons for Creating the Guidelines Advances in instrumentation and the information that can be obtained from the TEE examination has proceeded at a breath-taking pace since the introduction of this technology in the early 1980s. Recognizing the importance of TEE in the management of surgical patients, the American Society of Anesthesiologists and the SCA published practice guidelines for the clinical application of perioperative TEE in 1996.3 However, despite a large and growing body of literature on TEE, the ASE and the SCA have not endorsed a uniform set of standards for image acquisition and nomenclature specific for TEE to facilitate the conduct and reporting of routine studies. Members of the ASE Council for Intraoperative Echocardiography believed that creating a document that described in detail a comprehensive TEE examination using standard nomenclature would be useful for clinical care, quality assurance, education, and research purposes. Standard nomenclature and imaging planes would facilitate comparisons of studies performed in different patients, by different echocardiographers, at different institutions, or at different times. Standard nomenclature and imaging planes would also facilitate the conduct and storage of a comprehensive examination in a digital format and improve the ability to communicate findings in a consistent and unambiguous fashion. In addition, standard guidelines would provide a framework for training and education in TEE for future cardiologists and cardiovascular anesthesiologists. Presently, controversy still exists in the agreement between echocardiographic criteria based on investigations performed using transthoracic echocardiography to examinations performed using TEE and vice versa. Creating a standard set of TEE cross-sectional imaging planes will encourage the development of echocardiographic criteria specific to TEE for diagnosis and quantifying the severity of disease. At the same time a standard set of images that correlate with images obtained using transthoracic echocardiography would serve to enhance the ability to combine information obtained from either modality yet recognize their inherent differences, advantages, and limitations. How the Guidelines were Created The decision to develop a standard set of guidelines for the intraoperative TEE examination was made at the annual meeting of the Council for Intraoperative Echocardiography of the ASE in June, 1997. The project focused on describing an idealized TEE examination in a normal individual and organized according to anatomic structures that can be examined by TEE. Contributions detailing the normal examination of specific structures were solicited from nationally recognized experts in intraoperative TEE from cardiology and anesthesiology, many of whom were also members of the SCA Task Force for Certification in Perioperative Transesophageal Echocardiography. The contributions were compiled and edited by a central writing group to ensure that the methodology and descriptive terminology used was consistent throughout the manuscript. Based on the input received, it was determined that the most important parts of the TEE examination could be displayed in a set of 20 cross sectional imaging planes. These 20 cross sections would provide also the format for digital acquisition and storage of a comprehensive TEE examination. Because variability exists in the precise anatomic orientation between the heart and the esophagus in individual patients, an attempt was made to provide specific criteria based on identifiable anatomic landmarks to improve the reproducibility and consistency of image acquisition for each of the standard cross sections. Terminology was chosen for its ability to provide a precise and unambiguous identification and localization of anatomic structures that correlated to standards used for transthoracic echocardiography. Approval and Endorsement of the Guidelines Early drafts of the completed manuscript were distributed to all the contributors and members of the writing group to ensure that details were not lost or misconstrued in the rewriting process. Revised drafts were presented to the President of the ASE, President of the SCA, and Chairman of the ASE Committee for Nomenclature and Standards. Decisions and compromises were made to retain nomenclature and anatomic segmentation models based on precedents established in transthoracic echocardiography and the surgical literature. The final manuscript was presented to the officers of the SCA and ASE at their annual meetings in 1999 and endorsed after public debate and discussion. The manuscript was accepted for publication in the respective journals of each society after peer review.2 Use of the Guidelines in Clinical Care, Education, and Research The original intention was to use the guidelines as a template for the routine performance of intraoperative TEE examinations in the clinical setting. Within individual group practices, the guidelines may provide a consistent format for archiving, conveying, and reporting the results of studies. For training purposes, the guidelines can be used as a reference and a means to assess the technical quality and completeness of individual studies. The guidelines serve also to define standards and conventions that can be incorporated into questions used by the National Board of Echocardiography in their certification examinations to improve the objective assessment of knowledge in perioperative TEE. Establishing a standard set of cross sectional imaging planes improves also the ability to compare TEE studies to transthoracic studies, studies performed at different time points used for patient follow-up, and studies performed at different institutions by different echocardiographers for use in multicenter investigations. Finally, the basic set of cross-sectional images was designed to facilitate the recording and archiving of the complete examination in a digital format. It is the hope that these guidelines will also make it easier for industry to develop and refine their operating systems to permit quick and easy acquisition of echocardiographic data, save it into digital files, and allow for rapid search and retrieval. Future Directions An attempt was made to organize the guidelines in a common format that can integrate continued refinements in nomenclature and imaging technology as they are incorporated into clinical practice. Agreeing to adopt to an anatomic reference scheme of nomenclature was not possible because of conventions that had already been established. For this reason, terms such as transgastic, mid-esophageal, anterior, posterior, or inferior remain problematic. The exact location of the TEE probe within the esophagus or stomach cannot always be verified and the exact orientation of the heart to the esophagus or the major axis of the body is not always constant. The traditional use of the terms, "short-axis" and "long-axis," to describe the orientation of the imaging plane was expanded to apply to the examination of structures other than the left ventricle when using multiplane imaging. Further, it was recognized that it was difficult to distinguish each of the 4 apical left ventricular wall segments with certainty in the TEE left ventricular long-axis imaging planes using the 16 segment anatomic model for the left ventricle based on conventions established in the transthoracic echocardiographic examination.4 In accordance with the American Heart Association, the merits of a left ventricular model that contains only 3 apical segments for both TEE and the transthoracic examination are currently being debated. Finally, it was recognized that minor differences in image resolution and the imaging planes acquired using TEE studies make relying on echocardiographic criteria based primarily on transthoracic studies inaccurate under certain conditions. The creation of a standardized set of imaging planes will permit a clinical database of normal studies to be compiled to establish recognized normal ranges for standard echocardiographic measurements that are specific to TEE. Improving the ability to quantify the severity of disease based on TEE measurements and to distinguish disease states from normal or clinically insignificant variants will improve the usefulness of the TEE examination for clinical diagnosis and decision-making. References:
Albert T. Cheung, MD Jack S. Shanewise, MD Joseph S. Savino, MD © Society of Cardiovascular Anesthesiologists Questions or comments? Please send email to webmaster@scahq.org |