Echocardiography and Cardiac Ultrasound

Echocardiography uses high-frequency ultrasound to image the heart in real time, showing the size and motion of chambers and walls, the structure and function of valves, and - through the Doppler effect - the velocity and direction of blood flow. It is the principal noninvasive tool for assessing cardiac structure and function and is portable, radiation-free, and repeatable.

Definition

Echocardiography is the imaging of cardiac anatomy, motion, and blood flow using reflected ultrasound, combining two-dimensional and three-dimensional structural imaging with Doppler measurement of flow velocities.

Scope

This topic covers cardiac ultrasound as a diagnostic modality: the physical basis of ultrasound and Doppler imaging, the standard transthoracic and transesophageal approaches, and the core measurements of chamber size, ventricular function, and valvular flow. It is framed as a reference topic and does not provide thresholds for diagnosis or patient-specific management.

Core questions

• How do reflected ultrasound and the Doppler effect produce images of structure and measurements of flow?
• What can transthoracic and transesophageal approaches each reveal about chambers, walls, and valves?
• How are ventricular function and valvular disease quantified from echocardiographic data?

Key concepts

• Two-dimensional and three-dimensional imaging
• Doppler flow assessment
• Transthoracic and transesophageal windows
• Left ventricular ejection fraction
• Chamber quantification
• Valvular structure and function

Mechanisms

A transducer emits ultrasound pulses and detects their reflections from tissue interfaces, reconstructing real-time cross-sectional images of the chambers, walls, and valves. The Doppler principle - the frequency shift of ultrasound reflected from moving red cells - yields the velocity and direction of blood flow, allowing estimation of pressure gradients and the severity of stenosis or regurgitation. Standardised views and measurements, such as ejection fraction and chamber dimensions, make studies comparable across patients and over time (Lang, 2015; Mitchell, 2019). The transesophageal approach places the probe behind the heart for higher-resolution views of posterior structures.

Clinical relevance

Echocardiography is central to evaluating heart failure, valvular heart disease, and cardiomyopathies, and it supplies the structural and functional measurements that guideline pathways rely on, for example in hypertrophic cardiomyopathy (Ommen, 2020). The entry describes the modality's role and is not a basis for diagnosing or managing an individual patient.

Evidence & guidelines

Standard examination and measurement protocols are defined by American Society of Echocardiography recommendations for comprehensive transthoracic studies (Mitchell, 2019) and joint ASE/EACVI chamber-quantification recommendations (Lang, 2015). Disease-specific use is integrated into guidelines such as the AHA/ACC hypertrophic cardiomyopathy guideline (Ommen, 2020).

History

Cardiac ultrasound emerged in the 1950s when reflected ultrasound was first used to record motion of cardiac structures, evolving through M-mode and two-dimensional imaging to Doppler and three-dimensional techniques, and becoming the workhorse noninvasive cardiac imaging method of modern cardiology.

Seminal works

• lang-2015
• mitchell-2019

Frequently asked questions

What is the difference between transthoracic and transesophageal echocardiography?

Transthoracic echocardiography images the heart through the chest wall and is the standard first approach, while transesophageal echocardiography places the probe in the esophagus, close behind the heart, giving higher-resolution views of posterior structures such as the left atrium and mitral valve.

What does ejection fraction measure?

Left ventricular ejection fraction is the proportion of blood ejected from the left ventricle with each beat; it is a core echocardiographic measure of systolic function used to characterise heart-pump performance.