Transesophageal echocardiography with stress for the evaluation of patients with coronary artery disease.

When atherosclerosis significantly narrows the coronary lumen, limiting blood flow, the contraction of the underlying myocardium is impaired either at rest or during increases in myocardial oxygen demand. In fact, reduction in myocardial systolic wall thickening is the first phenomenon that develops following the onset of ischemia. 37,59 Further, the extent to which regional wall motion abnormalities secondary to myocardial ischemia affect global left ventricular function is one of the most important determinants of prognosis in ischemic heart disease. 11,12,39,46,57,58,86 Therefore, identification of areas of the myocardium with abnormal contraction patterns is critical for the diagnosis, prognostic stratification, and follow-up of patients with coronary artery disease (CAD). Echocardiography allows the assessment of myocardial contraction in real time and is therefore perfectly suited for its use in combination with different forms of stress designed to induce myocardial ischemia and unmask the presence of coronary stenoses. In addition, in cases of impaired myocardial contraction at rest, echocardiography can detect enhanced systolic wall thickening with inotropic stimulation, which differentiates viable from necrotic myocardium. Therefore, the use of cardiac ultrasound, alone or in conjunction with appropriate interventions, permits a comprehensive assessment of resting regional and global left ventricular function, the presence and extent of inducible myocardial ischemia, and the identification of myocardial viability. Accordingly, stress echocardiography has become a valuable tool for the evaluation of patients with known or suspected CAD. Because this technique relies on the visual assessment of changes in regional wall motion, optimal endocardial border delineation is critical for the accurate and reproducible interpretation of stress echocardiograms. A major limitation of the routine transthoracic echocardiographic examination, however, is the significant attenuation that may occur in some patients, particularly in those who are obese, elderly, or have a history of chronic obstructive pulmonary disease or previous open-heart surgery. Because these conditions are commonly encountered in patients referred for stress echocardiography, it is not infrequent that a suboptimal echocardiogram limits the performance or interpretation of the study. The exact prevalence of inadequate transthoracic echocardiograms for the successful completion and interpretation of stress echocardiography is difficult to estimate but, in the medical literature, has ranged from 0% to 20%. 9,51,77 Undoubtedly, this value varies from laboratory to laboratory and depends on the population undergoing the test, the availability of the latest advances in cardiac ultrasound that improve endocardial border delineation (e.g., second harmonics or the use of intravenous contrast agents that opacify the left ventricular cavity), the skills of the sonographer, and the expertise of the interpreting physician. Transesophageal echocardiography overcomes the limitations of the transthoracic examination by obtaining images with a tranducer positioned within the esophagus. The acoustic impedance is significantly reduced and the images are of a much higher quality in virtually every patient. In fact, transesophageal echocardiography is routinely used in several clinical situations in which the transthoracic examination has been found to have significant limitations 29,78 (e.g., prosthetic valves, atrial septal defects, suspected aortic dissection, and masses or thrombi in the atria). Recently, the transesophageal approach has become a valuable technique for stress echocardiography. The present article, therefore, focuses on the use of transesophageal echocardiography in combination with stress for the evaluation of patients with known or suspected CAD.