Echocardiogram

Echocardiography is the use of ultrasound to produce real-time images of the heart and associated cardiovascular structures. An individual examination is commonly called an echocardiogram.

Echocardiography can visualize the cardiac chambers, myocardium, valves, septa, pericardium, proximal great vessels, and patterns of intracardiac blood flow. Because images can be acquired continuously throughout the cardiac cycle, echocardiography provides both anatomical and functional information.

It is one of the most widely used cardiac imaging techniques because it is noninvasive in its standard transthoracic form, does not use ionizing radiation, and can be performed repeatedly to assess changes in cardiac structure and function.

Principle of Echocardiography

Echocardiography uses high-frequency sound waves generated by an ultrasound transducer. These waves travel through tissues and are reflected at interfaces between structures with different acoustic properties.

Returning echoes are detected by the transducer and processed to create images of the heart.

Ultrasound Transducer

The transducer contains piezoelectric elements that convert electrical energy into ultrasound waves and returning sound waves into electrical signals.

Position and orientation of the transducer determine the plane through which cardiac anatomy is displayed.

Why the Heart Can Be Imaged With Ultrasound

The heart contains multiple interfaces among myocardium, blood, valves, pericardium, and adjacent tissues. These interfaces generate different ultrasound reflections that allow cardiac structures to be distinguished.

Blood generally appears relatively dark on conventional two-dimensional echocardiography, while tissue interfaces produce brighter echoes.

Acoustic Windows

The lungs and ribs can interfere with transmission of ultrasound. Echocardiographic imaging therefore uses specific acoustic windows where the heart can be approached with less interference from air-filled lung and bone.

Common windows include parasternal, apical, subcostal, and suprasternal positions.

Major Types of Echocardiography

Technique	Approach	Major Use
Transthoracic echocardiography	Transducer placed on chest wall	Routine structural and functional cardiac assessment
Transesophageal echocardiography	Transducer positioned within esophagus	High-resolution imaging of selected posterior cardiac structures and valves
Stress echocardiography	Images obtained before and during or after cardiac stress	Assessment of inducible wall-motion abnormalities and selected valve conditions
Intracardiac echocardiography	Catheter-mounted transducer within the heart	Guidance during selected catheter procedures

Transthoracic Echocardiography

Transthoracic echocardiography (TTE) is the standard noninvasive echocardiographic examination. The transducer is placed at different positions on the chest and upper abdomen to obtain complementary views of the heart.

TTE can assess chamber size, ventricular contraction, wall thickness, valve morphology, blood flow, pericardial fluid, and many congenital and acquired abnormalities.

Parasternal Window

The parasternal window is typically obtained with the transducer positioned along the left sternal border.

From this location, long-axis and short-axis views can be obtained by changing the orientation of the ultrasound beam.

Parasternal Long-Axis View

The parasternal long-axis view displays a longitudinal section through the heart.

Structures commonly visualized include the left ventricle, interventricular septum, posterior left ventricular wall, left atrium, mitral valve, aortic valve, aortic root, and portions of the right ventricle.

Parasternal Short-Axis View

The parasternal short-axis view provides transverse sections through the heart at different levels.

Depending on transducer angulation, images can be obtained through the aortic valve, mitral valve, papillary muscles, or ventricular apex.

Short-Axis View at the Papillary Muscles

At the midventricular level, the left ventricle appears approximately circular in cross-section, while the right ventricle lies anteriorly and has a crescent-shaped appearance.

The anterolateral and posteromedial papillary muscles can be seen within the left ventricular cavity.

Apical Window

The apical window is obtained near the cardiac apex.

Several important views can be generated from this position, including the apical four-chamber, two-chamber, and long-axis views.

Apical Four-Chamber View

The apical four-chamber view displays both atria and both ventricles simultaneously.

It is useful for comparing chamber dimensions, examining the interatrial and interventricular septa, evaluating the mitral and tricuspid valves, and assessing ventricular contraction.

Apical Two-Chamber View

The apical two-chamber view primarily demonstrates the left atrium and left ventricle.

It provides another plane for assessing left ventricular wall motion and chamber size.

Apical Three-Chamber View

The apical three-chamber view, also called the apical long-axis view, includes the left atrium, left ventricle, mitral valve, left ventricular outflow tract, aortic valve, and proximal ascending aorta.

Subcostal Window

The subcostal window is obtained from the upper abdomen with the ultrasound beam directed toward the heart.

It can provide useful views of the four cardiac chambers, atrial septum, inferior vena cava, and pericardial space.

Inferior Vena Cava

The inferior vena cava can be imaged as it approaches the right atrium.

Its diameter and respiratory variation can contribute to estimation of right atrial pressure in the appropriate clinical context.

Suprasternal Window

The suprasternal window is obtained from the suprasternal notch.

It can demonstrate the aortic arch, proximal branch vessels, and portions of the descending thoracic aorta.

Two-Dimensional Echocardiography

Two-dimensional echocardiography produces moving cross-sectional images of the heart.

It is the foundation of routine echocardiographic assessment and allows direct visualization of cardiac structures throughout systole and diastole.

M-Mode Echocardiography

M-mode records the motion of structures along a single ultrasound line over time.

It provides very high temporal resolution and can be used for selected measurements of cardiac dimensions and motion.

Three-Dimensional Echocardiography

Three-dimensional echocardiography acquires volumetric cardiac data that can be reconstructed into three-dimensional views.

It is particularly useful for evaluating complex valve anatomy, chamber volumes, septal defects, and guiding selected structural heart procedures.

Doppler Echocardiography

Doppler echocardiography uses frequency changes in reflected ultrasound waves to evaluate the velocity and direction of moving blood.

It provides physiological information that complements the anatomical images obtained with two-dimensional echocardiography.

Pulsed-Wave Doppler

Pulsed-wave Doppler measures blood velocity at a selected location along the ultrasound beam.

It is useful when the examiner needs to determine flow characteristics at a specific anatomical site.

Continuous-Wave Doppler

Continuous-wave Doppler measures high blood velocities along the entire path of the ultrasound beam.

It is particularly useful for evaluating high-velocity jets produced by stenotic valves or regurgitant flow.

Color Doppler

Color Doppler superimposes color-coded flow information on the two-dimensional cardiac image.

It helps identify the location, direction, and spatial distribution of blood flow, including abnormal jets across valves or septal defects.

Tissue Doppler

Tissue Doppler imaging measures the velocity of myocardial tissue rather than blood.

It can provide information about ventricular systolic and diastolic function.

Blood Flow Velocity

Doppler measurements allow blood velocity to be quantified across valves, vessels, and selected intracardiac regions.

Changes in velocity can provide evidence of obstruction or abnormal pressure gradients.

Pressure Gradients

The pressure difference across a narrowed valve or other high-velocity jet can be estimated from Doppler velocity using the simplified Bernoulli equation:

Pressure Gradient ≈ 4 × Velocity²

This relationship is widely used in echocardiographic assessment of stenotic valves.

Right Atrium

The right atrium receives systemic venous blood through the superior and inferior venae cavae and venous blood from the myocardium through the coronary sinus.

Echocardiography can evaluate right atrial size, masses, pressure-related changes, and relationships with the tricuspid valve and atrial septum.

Right Ventricle

The right ventricle lies predominantly anteriorly and has a complex geometry.

Echocardiography evaluates its size, wall motion, systolic function, and relationship with the tricuspid valve and pulmonary outflow tract.

Left Atrium

The left atrium lies posteriorly and receives oxygenated blood from the pulmonary veins.

Left atrial enlargement can occur with chronic elevation of left ventricular filling pressure, mitral valve disease, and several other cardiovascular conditions.

Left Ventricle

The left ventricle has the thickest myocardial wall of the four chambers because it pumps blood through the systemic circulation.

Echocardiography can measure ventricular dimensions, wall thickness, chamber volume, global systolic function, and regional wall motion.

Interventricular Septum

The interventricular septum separates the right and left ventricles.

Its thickness and motion can be assessed directly, and echocardiography can detect many ventricular septal defects.

Interatrial Septum

The interatrial septum separates the atria.

It can be examined for septal defects, abnormal mobility, and other structural abnormalities, with transesophageal imaging providing particularly detailed visualization in selected cases.

Mitral Valve

The mitral valve lies between the left atrium and left ventricle and contains anterior and posterior leaflets.

Echocardiography can evaluate leaflet morphology, motion, coaptation, calcification, stenosis, regurgitation, chordae tendineae, and papillary muscle relationships.

Tricuspid Valve

The tricuspid valve lies between the right atrium and right ventricle.

Echocardiography evaluates its leaflets, annulus, supporting structures, and associated patterns of stenosis or regurgitation.

Aortic Valve

The aortic valve lies between the left ventricular outflow tract and ascending aorta.

It normally contains three semilunar cusps and can be evaluated for morphology, calcification, restricted opening, regurgitation, and associated aortic root abnormalities.

Pulmonary Valve

The pulmonary valve lies between the right ventricular outflow tract and pulmonary trunk.

Although it can be more difficult to visualize than other valves, echocardiography can assess its motion and Doppler flow characteristics.

Valve Stenosis

Valvular stenosis restricts forward blood flow through a valve.

Echocardiography can directly assess valve anatomy and use Doppler measurements to evaluate flow velocity and pressure gradients across the narrowed opening.

Valve Regurgitation

Valvular regurgitation occurs when a valve fails to close adequately, allowing blood to flow backward.

Color and spectral Doppler techniques help identify and quantify abnormal regurgitant flow.

Aortic Stenosis

In aortic stenosis, the aortic valve opening becomes restricted.

Echocardiographic evaluation includes valve morphology, peak velocity, pressure gradients, valve area, left ventricular wall thickness, and ventricular function.

Mitral Stenosis

Mitral stenosis restricts blood flow from the left atrium into the left ventricle.

Echocardiography can demonstrate leaflet thickening and restricted movement and can assess the hemodynamic severity of obstruction.

Mitral Regurgitation

Mitral regurgitation permits systolic blood flow from the left ventricle back into the left atrium.

Echocardiography evaluates the valve leaflets, annulus, chordae, papillary muscles, ventricular geometry, and characteristics of the regurgitant jet.

Tricuspid Regurgitation

Tricuspid regurgitation allows systolic blood flow from the right ventricle into the right atrium.

The Doppler velocity of the regurgitant jet can also contribute to estimation of pulmonary artery systolic pressure when appropriate assumptions are met.

Left Ventricular Systolic Function

Echocardiography is routinely used to evaluate how effectively the left ventricle contracts.

Assessment includes global ventricular function and regional movement of individual myocardial segments.

Ejection Fraction

Left ventricular ejection fraction (LVEF) is the proportion of end-diastolic ventricular volume ejected during systole.

It can be expressed as:

Ejection Fraction = (End-Diastolic Volume − End-Systolic Volume) / End-Diastolic Volume × 100

Regional Wall Motion

The left ventricular wall is divided into anatomical segments for systematic assessment.

Reduced or absent contraction in a regional pattern can indicate myocardial ischemia, infarction, scar, or other localized myocardial abnormalities.

Wall Motion Abnormalities

A myocardial segment may be described according to the degree and direction of movement during systole.

• Hypokinesia: reduced contraction
• Akinesia: absent contraction
• Dyskinesia: paradoxical outward motion during systole

Diastolic Function

Echocardiography can assess left ventricular filling and relaxation using transmitral blood flow, tissue Doppler velocities, left atrial size, and other measurements.

These findings contribute to assessment of ventricular diastolic function and filling pressures.

Cardiac Output

Doppler echocardiography can estimate stroke volume by combining the cross-sectional area of an outflow tract with the distance traveled by blood during systole.

Cardiac output can then be calculated from stroke volume and heart rate.

Pericardium

The pericardium surrounds the heart and proximal portions of the great vessels.

Echocardiography is highly useful for detecting fluid within the pericardial cavity and evaluating its effect on cardiac filling.

Pericardial Effusion

A pericardial effusion is abnormal accumulation of fluid within the pericardial cavity.

On echocardiography, fluid commonly appears as an echo-free or relatively dark space surrounding portions of the heart.

Cardiac Tamponade

Cardiac tamponade occurs when elevated pericardial pressure impairs filling of the cardiac chambers.

Echocardiography can demonstrate findings associated with hemodynamic compromise, including abnormal chamber collapse and respiratory variation in blood flow.

Intracardiac Masses

Echocardiography can detect masses within the cardiac chambers or attached to valves and endocardial surfaces.

Possible findings include thrombi, tumors, and vegetations, although further imaging may be required for complete tissue characterization.

Left Ventricular Thrombus

Thrombus can form within poorly contracting portions of the left ventricle, particularly after large myocardial infarction or in severe ventricular dysfunction.

Echocardiography can visualize many ventricular thrombi, and ultrasound contrast agents may improve detection when endocardial definition is limited.

Vegetations

Infective endocarditis can produce irregular masses called vegetations on valve leaflets or other endocardial surfaces.

Echocardiography is central to evaluation of suspected endocarditis and associated structural complications.

Congenital Heart Disease

Echocardiography is fundamental to diagnosis and follow-up of congenital heart disease.

It can demonstrate abnormal chamber connections, septal defects, valve abnormalities, outflow obstruction, and abnormal relationships of the great vessels.

Atrial Septal Defect

An atrial septal defect creates an abnormal communication between the atria.

Two-dimensional and Doppler imaging can demonstrate the defect and associated interatrial blood flow.

Ventricular Septal Defect

A ventricular septal defect creates an abnormal communication between the ventricles.

Color Doppler is particularly useful for identifying the abnormal jet through the septal opening.

Bubble Study

An agitated saline contrast study, commonly called a bubble study, can be performed during echocardiography to investigate selected intracardiac or intrapulmonary shunts.

Microbubbles introduced into a peripheral vein normally opacify the right-sided cardiac chambers.

Transesophageal Echocardiography

Transesophageal echocardiography (TEE) places an ultrasound transducer within the esophagus.

Because the esophagus lies directly posterior to the heart, TEE can obtain high-resolution images without much of the interference produced by the chest wall, ribs, and lungs.

Anatomical Relationship of the Esophagus and Heart

The esophagus passes immediately posterior to the left atrium.

This close anatomical relationship makes TEE particularly useful for imaging the left atrium, atrial septum, left atrial appendage, mitral valve, aortic valve, and portions of the thoracic aorta.

Uses of Transesophageal Echocardiography

• Detailed valve assessment
• Evaluation for left atrial appendage thrombus
• Assessment of suspected endocarditis
• Evaluation of atrial septal abnormalities
• Imaging of portions of the thoracic aorta
• Guidance during cardiac surgery and structural heart procedures

Left Atrial Appendage

The left atrial appendage is a muscular pouch extending from the left atrium.

TEE provides detailed visualization of this structure and is commonly used to evaluate for thrombus in selected patients with atrial fibrillation.

Stress Echocardiography

Stress echocardiography compares cardiac function at baseline with function during or immediately after increased cardiac workload.

Stress may be produced by exercise or pharmacological agents.

Stress-Induced Ischemia

A coronary artery with significant flow limitation may provide adequate blood flow at rest but fail to meet increased myocardial demand during stress.

This can produce new or worsening regional wall-motion abnormalities on echocardiography.

Contrast Echocardiography

Ultrasound-enhancing agents containing microbubbles can be administered intravenously to improve visualization of the blood pool.

They can improve endocardial border definition and assist in selected assessments of ventricular function and intracardiac abnormalities.

Strain Imaging

Myocardial strain imaging evaluates deformation of the myocardium during contraction and relaxation.

Speckle-tracking echocardiography can measure patterns of myocardial deformation that may reveal functional abnormalities not apparent from ejection fraction alone.

Global Longitudinal Strain

Global longitudinal strain reflects shortening of the left ventricular myocardium along its long axis.

It is used in selected clinical settings to provide additional quantitative assessment of myocardial function.

Great Vessels

Echocardiography can visualize portions of the ascending aorta, aortic root, pulmonary trunk, venae cavae, and other proximal vessels.

The degree of visualization depends on the acoustic window and echocardiographic technique.

Aortic Root

The aortic root includes the aortic valve, annulus, sinuses, and proximal ascending aorta.

Echocardiography can assess aortic root dimensions, valve relationships, dilation, and selected structural abnormalities.

Pulmonary Artery Pressure

Echocardiography can estimate pulmonary artery pressures indirectly using Doppler measurements and other hemodynamic findings.

These estimates are useful for screening and follow-up but are distinct from direct pressure measurement by cardiac catheterization.

Advantages of Echocardiography

• No ionizing radiation
• Real-time cardiac imaging
• Portable and widely available
• Assessment of anatomy and function in the same examination
• Doppler evaluation of blood flow
• Repeatable for serial follow-up
• Standard transthoracic examination is noninvasive

Limitations of Echocardiography

Image quality depends on the available acoustic windows and can be reduced by body habitus, lung interference, chest wall anatomy, patient positioning, or other factors.

Some structures may therefore require transesophageal echocardiography, CT, MRI, or another imaging technique for complete evaluation.

Echocardiography Compared With CT and MRI

Feature	Echocardiography	Cardiac CT	Cardiac MRI
Radiation	None	Uses ionizing radiation	None
Real-time imaging	Excellent	Limited compared with ultrasound	Cine imaging available
Valve assessment	Major strength	Detailed structural anatomy	Structure and flow assessment
Coronary arteries	Limited routine visualization	Major strength	More limited routine role
Myocardial tissue characterization	Limited	Selected applications	Major strength
Portability	High	Low	Low

Common Clinical Applications

Clinical Question	Echocardiographic Assessment
Heart failure	Ventricular size, ejection fraction, wall motion, valves and filling patterns
Valve disease	Valve anatomy, stenosis, regurgitation and hemodynamic consequences
Myocardial infarction	Regional wall motion, ventricular function and mechanical complications
Pericardial disease	Effusion and hemodynamic effects
Congenital heart disease	Septal defects, chamber connections and great-vessel relationships
Endocarditis	Vegetations, valve damage and complications
Cardiac masses	Location, mobility and relationship to cardiac structures

Key Features of Echocardiography

Feature	Key Point
Imaging method	Ultrasound
Standard approach	Transthoracic echocardiography
Major views	Parasternal, apical, subcostal and suprasternal
Flow assessment	Doppler echocardiography
Major functional measurement	Ventricular systolic and diastolic function
Major structural strengths	Chambers, valves, septa and pericardium
Radiation	No ionizing radiation

Anatomical and Clinical Importance

Echocardiography provides a direct moving view of cardiovascular anatomy. Instead of examining the heart only as a static structure, it shows chambers filling and emptying, ventricular walls contracting, valves opening and closing, and blood moving through the heart during each cardiac cycle.

The technique is especially valuable because anatomical and physiological information can be evaluated together. A stenotic valve can be seen directly while Doppler measures the accelerated blood flow across it, a damaged ventricular segment can be identified while overall ejection fraction is measured, and a septal defect can be visualized while color Doppler demonstrates blood passing through it.

Knowledge of cardiac anatomy is essential for interpreting echocardiographic views because each image represents a particular plane through a three-dimensional moving organ. Understanding the relationships among chambers, valves, septa, great vessels, and surrounding structures allows these ultrasound sections to be translated into meaningful cardiovascular anatomy.