Although transthoracic echocardiography remains the cornerstone of diagnostic cardiac ultrasound, transesophageal echocardiography (TEE) is a valuable complementary tool. As compared with transthoracic echocardiography, TEE offers superior visualization of posterior cardiac structures because of close proximity of the esophagus to the posteromedial heart with lack of intervening lung and bone. This proximity permits use of high-frequency imaging transducers that afford superior spatial resolution (image 1).
TEE displays most of the left ventricle (LV) with definition that is equal or superior to that achieved with transthoracic echocardiography. In particular, the full thickness of the myocardium, including the endocardium with its complex endo-architecture, is seen with clarity. However, most TEE views do not fully display the apical portion of the LV, which is truncated or foreshortened. This shortcoming lowers the sensitivity of TEE for detecting a wall motion abnormality limited to the apex, leads to underestimation of chamber volume, and may result in misinterpretation of global LV systolic function. Importantly, the presence of apical thrombus may be missed on TEE alone.
The use of TEE for the evaluation of the LV will be reviewed here. The specific roles for TEE in ischemic heart disease, valvular disease, and aortic pathology are discussed in detail separately. (See "Transesophageal echocardiography in the evaluation of aortic valve disease" and "Transesophageal echocardiography in the evaluation of mitral valve disease" and "Transesophageal echocardiography in traumatic rupture of the aortic isthmus".)
While quantitative methods to measure LV systolic function and ejection fraction by TEE have been described, most TEE evaluation of the LV is qualitative. Studies by anesthesiologists in the operating room have documented the validity of this approach for recognizing hypovolemia, the adverse effects of proximal cross-clamping of the aorta, and the influence of various anesthetic regimens on LV systolic function [1-6]. When evaluating left ventricular function, it is important to consider the patient's overall condition. Volume status, sedating medications, and general anesthesia may alter both systolic and diastolic function through their effects on preload and afterload.
Ejection fraction — Calculation of end-diastolic and end-systolic volumes by TEE using the biplane method of discs (ie, Simpson's rule) systematically underestimates LV size [7,8]. A non-volumetric method has been described that accurately estimates LV ejection fraction using the descent of the mitral annulus toward the apex as an index of the shortening of the ventricular long axis .