TEE in the Critical Care Setting
Solomon Aronson1
Scott T. Reeves2
Kim J. Payne2
James Ramsay2
Jack S. Shanewise2
Stephen Insler2
William J. Stewart2
1OUTLINE AUTHOR
2ORIGINAL CHAPTER AUTHORS
▪ KEY POINTS
Echocardiography is a Class 1 indication in the setting of hemodynamic instability and suspected aortic dissection.
Transesophageal echocardiography (TEE) provides superior resolution and overcomes the technical difficulties encountered with transthoracic echocardiography in the evaluation of the critically ill or injured patient.
TEE leads to changes in management in approximately 50% of critically ill and injured patients, regardless of whether a pulmonary artery catheter (PAC) is present.
Unexplained hypoxemia in a critically ill patient should prompt an echocardiographic assessment for patent foramen ovale.
Positive contrast echocardiography for PFO requires opacification of the right atrium (RA) and visualization of contrast in the left atrium (LA) within a few cardiac cycles
TEE is more sensitive and equally specific to transthoracic echocardiography in diagnosis of infective endocarditis (IE).
Endocarditic valve lesions are usually on the upstream side of a valve leaflet.
Mitral valve vegetations greater than 10 mm in size are associated with an almost 50% risk of embolization.
Fifty-six percent of patients following blunt chest trauma will have a pathologic diagnosis established following a TEE evaluation.
The most sensitive two-dimensional (2D) manifestation of cardiac tamponade is right ventricular collapse during diastole.
Acute valve injury may occur following blunt chest trauma, with injury to the aortic valve being most common.
Acute aortic dissection has a mortality of 1% per hour for the first 48 hours.
An intimal flap must be observed in two image planes to reliably make the diagnosis of aortic dissection.
TEE is emerging as one means to diagnose suspected hemodynamically significant pulmonary embolism.
I. CRITICAL CARE
In 2003 a task force cosponsored by the American College of Cardiology, American Heart Association, and American Society of Echocardiography published guidelines for clinical application of echocardiography, including trauma and critical care.
Several reports suggest significant changes in therapy or surgical intervention following TEE examination in many ICU populations including those with hypotension. In addition to imaging specific pathologies that may indicate a need for surgical repair or intervention, assessment of ventricular size permits differentiation between cardiac and noncardiac causes of hypotension.
A. Echocardiography versus the pulmonary artery catheter
Echocardiography can provide diagnostic information faster than the time required to place and obtain information from a PAC, and imaging provides a diagnostic capacity not available from the PAC.
Several investigators have found no correlation between LVSWI and FAC and postulate that changes in ventricular compliance, loading conditions, and ventricular function alter the pressure-volume relationship of the left ventricle in a manner that leads to discordant interpretations between the PAC and TEE.
The use of pressure parameters alone (from the PAC) can lead to erroneous conclusions regarding ventricular filling and function.
B. Unexplained hypoxemia
TEE is the technique of choice for detection of intracardiac shunt. In addition, the TEE exam provides an assessment of overall cardiac function and views of other intrathoracic pathology (pericardial or pleural effusions, collapsed portions of the lung, pulmonary embolus).
Echocardiographic detection of a PFO and associated intracardiac shunt requires visualization of the atrial septum, color flow mapping, and right-sided injection of echo contrast (contrast echocardiography).
A right-to-left shunt is diagnosed if microbubbles appear in the LA within three to five cardiac cycles of RA opacification; late appearance can be due to transpulmonary flow. Crude quantification is possible with a small shunt defined as 3 to 10 bubbles, a medium shunt 10 to 20, and a large shunt greater than 20 bubbles.
C. Suspected endocarditis
IE may present as critical illness (cardiac failure, dysrhythmias, sepsis), and critically ill patients may develop endocarditis due to infection of indwelling devices and the presence of an immunocompromised state.
Strict diagnostic criteria for IE were originally proposed by von Reyn et al. in 1981 and were then revised by Durack et al. in 1994 (the “Duke” criteria).
In an evaluation of the Durack criteria in more than 100 patients with IE, Roe et al. found that TEE was critically important, resulting in a diagnostic reclassification in approximately 25% of patients, 90% of which were from “possible” to “definite” IE.
The hallmark lesion of IE is the vegetation, defined as a mass adherent to the endocardium consisting of pathologic microorganisms interwoven with platelets, fibrin strands, and blood cells usually presenting on the “upstream” side of a regurgitant valve. The echocardiographic appearance is an echodense mass exhibiting a variable amount of independent motion.
The echocardiographic exam for IE should be a complete, standard exam including careful, multiplane imaging of all the valves and associated structures, as well as complete Doppler echocardiographic assessment.
Investigations have compared TTE with TEE in the diagnosis of IE. These studies have demonstrated a sensitivity of TTE of 28% to 63% versus 86% to 100% with TEE.
