Publications

Because of the better resolution of higher frequency transducers and the proximity of the coronary arteries to the esophageal window, TEE is emerging as a valuable method for evaluation of coronary artery disease. TEE allows imaging of the proximal coronary arteries, measurement of coronary flow reserve, identification of coronary artery anomalies, and observation of wall motion during transesophageal atrial pacing. The application of TEE in evaluation of coronary artery disease will continue to grow as technology improves.

The superior imaging capabilities of TEE have rapidly thrust this technique into the mainstream of noninvasive cardiology. However, the semi-invasive nature of this procedure requires specialized training on the part of the echocardiographer and adaptations of the traditional echocardiographic laboratory. These requirements will become even more evident as this technique is employed increasingly for interventional studies such as transesophageal atrial pacing and pharmacologic stress. TEE has proved efficacious and safe, even in critically ill patients, and its applications continue to expand. Following an article on anatomy, encompassing single and biplane orientation, the remainder of this monograph addresses the established as well as the emerging applications of TEE.

Many echocardiographic signs of severe MR are clearly demonstrated, particularly when both TEE and TTE are used. When these signs are assiduously sought, the recognition of severe MR should pose little problem. Part of the confusion concerning MR and the grading of its severity comes from the fact that the hemodynamic consequences of a given degree of MR vary widely from one individual to another. A regurgitant volume of 50 mL might prove incapacitating to one patient while seeming inconsequential in a second patient. A regurgitant fraction of 50% is poorly tolerated in some patients and asymptomatic in others. Similarly, a regurgitant orifice 0.5 cm2 has unpredictable consequences to the organism, and, in fact, this orifice may vary considerably in size depending on hemodynamic conditions. Thus, a universal definition of the severity of MR is lacking, and there is no agreement on the units with which to quantitate it. The net effect of this confusion is not an inability to recognize severe MR but frustration in differentiating moderate MR from severe MR. We believe that precise quantitation of MR will occur when comprehensive pharmacologic interventions with either TEE or surface echocardiographic monitoring are performed to define the severity of MR by its range of responses to these agents. We have had some success with Doppler measurement of the response of pulmonary artery pressure to dynamic exercise. Patients with normal pulmonary artery pressure at rest tend to show exaggerated rises in pulmonary pressure when MR is clinically important and has resulted in left ventricular dysfunction. Anticipated progress notwithstanding, competently performed TEE is the method of choice for recognizing severe MR.

Transesophageal echocardiography is ideally suited for imaging during CPR because high-quality images can be obtained immediately and continuously without interruption of cardiac compression and ventilation. Use of TEE during CPR is increasing to help monitor resuscitative efforts, for diagnosis, to assist in understanding the physiology of blood flow, and for evaluation of new methods of CPR.