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Intraoperative transoesophageal echocardiography (TOE) usually provides reliable information on the following:

True / False

Measurements during anaesthesia will usually be the same as preoperative values Correct

Assessing adequacy of mitral valve repair for mitral regurgitation Correct

Measurement of intracardiac pressures Incorrect answer selected

Management of intravascular volume Correct

Aortic valve velocities and gradients Correct

Explanation

Transoesophageal echocardiography (TOE) is a useful modality for monitoring patients for a wide variety of major cardiac and non-cardiac procedures. It is strongly recommended for intraoperative management of valve repair or replacement. TOE can assess the adequacy of mitral valve repair, as well as the presence of a number of complications such as systolic anterior motion and mitral stenosis.

Intraoperative transoesophageal measurements may be affected by anaesthesia and surgery, so may differ from preoperative transthoracic echocardiography data. In patients with aortic stenosis, intraoperative measurements of valve velocities and gradients with transoesophageal echocardiography are often lower compared to preoperative measurements with transthoracic echocardiography.

There are practical limitations to what TOE can do, and what information should be appropriately taken intraoperatively.

The TOE probe sits in the oesophagus or stomach, and is therefore much closer to the heart. This means that generally the resolution is significantly higher than with transthoracic echocardiography. However, as the probe position is restrained by the oesophagus and stomach, views of structures distant from the probe can be limited such as the ventricular apex. In addition to 2D imaging, spectral Doppler is a key tool for assessing the heart, and this requires direct alignment with the target. This makes it difficult to assess the severity of aortic stenosis.

Because the loading conditions under anaesthesia differ significantly from the normal awake state, the severity of mitral and aortic regurgitation should not normally be formally assessed under anaesthesia, as these are usually underestimated. Useful information can be gleaned from TOE, which can help titrate fluid filling.

Intracardiac pressures can normally be estimated by using regurgitant flow across a valve into a chamber using the modified Bernoulli equation or by vessel size and collapsibility. However, they cannot be measured by echocardiography.

Reference:

Dawes T, Price S. Transoesophageal echocardiography in high risk surgery. Contin Educ Anaesth Crit Care Pain. 2013;13:165-173.

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