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Echocardiography: Transeophageal and Stress Echocardiography

Transesophageal echocardiography offers superior assessment of cardiac anatomy and physiology because of the proximity of the probe. Echocardiography is often used as an imaging modality to increase the sensitivity and specificity of exercise stress tests for the detection of CAD.
        

Transeophageal Echocardiography

• A similar study to a surface echocardiogram, however, the ultrasound probe is passed into the esophagus to examine the cardiac structures in close proximity. Transesophageal echocardiography offers superior assessment of cardiac anatomy and physiology because of the proximity of the probe.

• The most common indications for a transesophageal echocardiographic (TEE) examination are:

  • Evaluation for left atrial appendage thrombus prior to elective cardioversion of atrial fibrillation or atrial flutter
  • Examine the valves for vegetations
  • Evaluation of prosthetic valve function
  • Evaluation for a thrombus in patients with a stroke or other embolic phenomenon
  • Evaluation of aneurysm or dissection of the aorta
  • Evaluation for intracardiac masses, tumors, or thrombi
  • Evaluation of congenital heart disease

• A TEE is a relatively safe procedure. The most common adverse events are related to the mechanical effects of the probe in the esophagus and include retching, vomiting, and transient hypoxia.

• Contraindications to performing a TEE examination are related to esophageal pathology and include the following:

  • Esophageal stricture or malignancy
  • Esophageal ulcer or varices, especially with recent hemorrhage
  • Zenker diverticulum
  • Altered mental status or an uncooperative patient
  • History of dysphagia or odynophagia

Stress Echocardiography

• Echocardiography is often used as an imaging modality to increase the sensitivity and specificity of exercise stress tests for the detection of CAD. Stress echocardiography also assesses myocardial viability in patients with known CAD and in whom revascularization is being considered.

• The hallmark of an abnormal stress echocardiogram is loss of contractile function as HR and, consequently, myocardial oxygen demand increase. Both physical exercise (ie, treadmill) and pharmacologic stress (dobutamine) are used to achieve the appropriate workload, which is 85% of the age predicted maximum HR.

• Vasodilators (ie, adenosine, dipyridamole) that are used with nuclear myocardial perfusion imaging are usually not helpful in stress echocardiography because they lack sensitivity.

• Indications for stress echocardiography include the following:

The detection of coronary artery disease in intermediate- risk patients presenting with chest pain, ECG abnormalities, or prior to noncardiac surgery especially when baseline ECG abnormalities render treadmill testing insensitive.

For risk stratification in patients with known CAD or who are post-MI.

• Contraindications to stress echocardiography include the following:

  • Uncontrolled arrhythmias
  • Acute MI
  • Unstable angina
  • Hemodynamically significant left ventricular outflow tract obstruction
  • Severe aortic stenosis
  • Aortic dissection

• The exercise echocardiography exhibits sensitivity between 79% and 85% and a specificity of 80% to 87%. As with treadmill stress testing, the diagnostic accuracy improves as the coronary disease severity increases. Dobutamine stress echocardiography has a sensitivity of 80% and a specificity of 84% to detect coronary ischemia.

• The accuracy of stress echocardiography is limited in patients with a left bundle-branch block or ventricular paced rhythm because baseline wall motion abnormalities are induced by abnormal ventricular depolarizations. In these patients nuclear perfusion scans are more likely to provide useful information. In patients who have poor acoustic windows, the stress echocardiogram is usually nondiagnostic.

 

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