Transthoracic Echocardiography (TTE) slices: Focused Cardiac Ultrasound (FoCUS) approach

Echocardiography is an essential tool for rapidly assessing the structure and function of the heart, particularly in emergency or critical care settings. FoCUS (Focused Cardiac Ultrasound) focuses on a targeted, limited assessment of vital cardiac functions, providing crucial real-time information to guide clinical decisions. It is particularly useful in cases of shock, hypotension or suspected acute cardiac dysfunction.

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Introduction to FoCUS

FoCUS is a limited echocardiography, aimed at answering specific clinical questions, such as:

- Overall systolic function: Does the heart pump efficiently?

- Intravascular volume: Does the patient show signs of volume overload or deficit?

- Pericardial effusion: Is there any pericardial fluid that could indicate tamponade?

- Right ventricular function: Are there any signs of right ventricular overload, as in the case of pulmonary embolism?

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Key Views in FoCUS

In the FoCUS approach, only a few key sections are used to provide rapid and essential information about the heart. These slices can be used to assess critical points in the heart and guide immediate clinical decisions.

• Transthoracic Echocardiography (TTE) in the FoCUS Context:

ETT is the standard approach for performing FoCUS. The probe is placed on the patient's chest to rapidly visualize essential cardiac structures. Unlike comprehensive echocardiography, FoCUS is fast, non-invasive and can be performed at the patient's bedside.

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Key cuts in FoCUS

1. Subxyphoid (Subcostal) section  

The subxyphoid section is obtained by placing the ultrasound probe under the xyphoid process, at the base of the sternum, with the marker oriented at 3 o'clock and the probe pointing towards the patient's head. 

It allows visualization of the left and right ventricles, left and right atria, and mitral and tricuspid valves.

- Interpretation: Allows assessment of ventricular size and function, as well as valve morphology and function.

2. Parastern Long Axis Section  

The parasternal long-axis section is a longitudinal view of the heart obtained by placing the ultrasound probe on the left side of the chest, at the level of the 3rd or 4th intercostal space, with the marker pointing towards the right shoulder.

It allows visualization of the left and right ventricles, the left and right atria, and the aortic and mitral valves.

- Interpretation: Allows assessment of ventricular size and function, as well as valve morphology and function.

3. Small Axis Parastern Section  

The parasternal short-axis section is a cross-sectional view of the heart obtained by placing the ultrasound probe on the left side of the chest, at the level of the 3rd or 4th intercostal space, and then rotating it 90° clockwise from the parasternal long-axis section, with the marker pointing towards the left shoulder. 

It allows visualization of the left and right ventricles, left and right atria, and mitral and tricuspid valves.

- Interpretation: Allows assessment of ventricular size and function, as well as valve morphology and function.

4. Apical section 4 cavities  

The apical 4-cavity slice is a view obtained by placing the ultrasound probe at the apex of the heart, at the level of the 5th intercostal space, with the marker facing the patient's left (at 3 o'clock) and pointing downwards. 

It allows visualization of the left and right ventricles, left and right atria, and mitral and tricuspid valves.

- Interpretation: Allows assessment of ventricular size and function, as well as valve morphology and function.

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Use and interpretation in FoCUS

In FoCUS, each view is used to answer specific clinical questions quickly. Unlike a full echocardiogram, the aim is not to provide a detailed assessment of all cardiac structures, but to detect critical abnormalities that may require urgent intervention. For example:

- Sub-Xyphoidal sectioning is particularly useful for detecting pericardial effusion, which can lead to cardiac tamponade.

- The Small Axis Parasternal Section assesses the overall function of the left ventricle in a matter of seconds.

- The Apical 4-Cavity Section visualizes the right ventricle and detects overload, often a sign of massive pulmonary embolism.

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Conclusion

FoCUS is a fast and essential tool for cardiac assessment in critical situations. The selected slices provide an overview of cardiac function, as well as the information needed to guide immediate patient management. Although limited in terms of comprehensiveness, it plays a major role in rapid decision-making at the patient's bedside.

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