The Transthoracic Echocardiogram

Step-By-Step Approach

Step 1: Clinical Data

▪ The indication for the study determines the focus of the examination.
▪ Key clinical history and physical examination findings and results of any previous cardiac imaging studies are noted.

Key Points

□ The goal of the echo study is to answer the specific question asked by the referring provider.
□ Blood pressure is recorded at the time of the echo, because many measurements vary with loading conditions.
□ Knowledge of clinical data ensures that the echo study includes all the pertinent images and Doppler data. For example, when a systolic murmur is present, the echo study includes data addressing all the possible causes for this finding.
□ Data from previous imaging studies may identify specific areas of concern, such as a pericardial effusion noted on chest computed tomography (CT) imaging.
□ Detailed information about previous cardiac procedures assists in interpretation of postoperative findings, evaluation of implanted devices (such as prosthetic valves or percutaneous closure devices), and detection of complications.
□ Use of precise anatomic terminology facilitates accurate communication of imaging results (Table 2.1).

Step 2: Patient Positioning

▪ A steep left lateral position provides acoustic access for parasternal and apical views (Fig. 2.1).
▪ The subcostal views are obtained when the patient is supine; if needed, the legs are bent to relax the abdominal wall.
▪ Suprasternal notch views are obtained when the patient is supine with the head turned toward either side.

Key Points

□ Images may be improved with suspended respiration, typically at end-expiration but sometimes at other phases of the respiratory cycle.
□ An examination bed with an apical cutout allows a steeper left lateral position, often providing improved acoustic access for apical views.
□ Imaging can be performed with either hand holding the transducer and with the examiner on either side of the patient. However, imaging from the patient’s left side avoids reaching over the patient and is essential for apical views when the patient’s girth is larger than the arm span of the examiner.
□ Prolonged or repetitive imaging requires the examiner to learn ergonomic approaches to minimize mechanical stress and avoid injury.

Step 3: Instrumentation Principles

▪ A higher transducer frequency provides improved resolution but less penetration of the ultrasound signal.
▪ Harmonic imaging is frequently used to improve image quality, particularly recognition of endothelial borders.
▪ Depth, zoom mode, and sector width are adjusted to optimize the image and frame rate, depending on the structure or flow of interest (Fig. 2.2).
▪ Gain settings are adjusted to optimize the data recording while avoiding artifacts.

TABLE 2.1

Terminology for Normal Echocardiographic Anatomy
Aorta∗	Sinuses of Valsalva Sinotubular junction Coronary ostia Ascending aorta Descending thoracic aorta Proximal abdominal aorta
Aortic valve	Right, left, and non-coronary cusps Nodules of Arantius Lambl excrescence
Mitral valve	Anterior and posterior leaflets Posterior leaflet scallops (lateral, central, medial) Chordae (primary, secondary, tertiary; basal, and marginal) Commissures (medial and lateral)
Left ventricle	Wall segments (see Chapter 8) Septum, free wall Base, apex Medial and lateral papillary muscles
Right ventricle	Inflow segment Moderator band Outflow tract (conus) Supraventricular crest Anterior, posterior, and conus papillary muscles
Tricuspid value	Anterior, septal, and posterior leaflets Chordae Commissures
Right atrium	RA appendage SVC and IVC junctions Valve of IVC (Chiari network) Coronary sinus ostium Crista terminalis Fossa ovalis Patent foramen ovale
Left atrium	LA appendage Superior and inferior left pulmonary veins Superior and inferior right pulmonary veins Ridge at junction of LA appendage and left superior pulmonary vein
Pericardium	Oblique sinus Transverse sinus

Key Points

□ Although the control panel varies for each instrument, the basic functions are similar for all ultrasound systems.
□ The highest frequency that penetrates adequately to the depth of interest is used for optimal imaging.
Fig. 2.1 Patient positioning for transthoracic echocardiography.The patient is positioned in a steep left lateral decubitus position on an examination bed with a removable section cut out of the mattress to allow placement of the transducer on the apex by the sonographer as shown. Ultrasound gel is used to enhance coupling between the transducer face and the patient’s skin. The sonographer sits on an adjustable chair and uses the left hand for scanning and the right hand to adjust the instrument panel. The room is darkened to improve visualization on the ultrasound instrument display screen.
□ With harmonic imaging, flat structures (such as valve leaflets) appear thicker than with fundamental imaging.
□ Frame rate is higher for a shorter depth or a narrower sector; a fast frame rate is especially important with Doppler color flow imaging.
□ Too narrow a sector may miss important anatomic or physiologic findings.
□ Excessive gain results in artifacts with both imaging and Doppler, whereas inadequate gain results in data loss.

Step 4: Data Recording

▪ Representative digital images from the echo study are saved to document the findings and for later review and measurement.
▪ Echo images include an electrocardiogram (ECG) tracing for timing purposes.
▪ A 2-beat cine loop is adequate for sinus rhythm; longer timed cycles are used when atrial fibrillation or other arrhythmia is present.

Key Points

□ Two-dimensional (2D) echo images in each view are recorded first with a depth and sector width that encompasses all the structures in the image plane and then at a depth and sector width optimized for the structures of interest (Fig. 2.3).
Fig. 2.2 Schematic diagram illustrating the typical features of a simplified echocardiographic instrument panel.Each ultrasound system has a unique instrument panel, ranging from simple to complex, often now integrated into an interactive screen rather than physical buttons. However, the functions controlled by the instrument panel fall into several basic categories as shown schematically here. Understanding the basic principles of ultrasound physics, imaging and Doppler parameters allow the operator to quickly master the interface for any given ultrasound system. Additional options are provided as needed for advanced imaging modalities, such as 3D imaging or speckle tracking strain.
Fig. 2.3 Parasternal long-axis view. (A) Initially images are recorded at a depth of 18 cm to show the structures posterior to the heart (top). (B) Next, images are recorded with the depth decreased to 13 cm and the resolution mode used (note that the top of the displayed image now is 2 cm from the skin) to focus on the aortic and mitral valves.
□ Additional zoom mode images of normal and abnormal findings are recorded as needed.
□ Three-dimensional (3D) imaging is used routinely for measurement of ventricular volumes and as needed for other cardiac structures (see Chapters 4 and 6).
□ Spectral pulsed and continuous-wave (CW) Doppler data are recorded with the baseline and velocity range adjusted so that the flow signal fits but fills the vertical axis. The time scale is adjusted to maximize the accuracy of measurements (usually an x-axis of 100 mm/s) (Fig. 2.4).
□ Color Doppler is recorded after sector width and depth are adjusted to optimize frame rate and gain is set just below the level that results in background speckle.
□ The variance mode on the color scale is preferred by many examiners (including the authors) to enhance recognition of abnormal flows.
□ Some normal flows result in a variance display—for example, when left ventricular (LV) outflow velocity exceeds the Nyquist limit and signal aliasing occurs (Fig. 2.5).

Step 5: Examination Sequence

▪ Subsequent chapters provide details on the elements of the examination for each clinical condition needed for a final diagnosis.
▪ These examination elements are incorporated into a systemic patient study sequence.

Key Points

□ There are several approaches to an examination sequence; any of these are appropriate if a complete systemic examination is performed.
□ In some clinical situations, a limited examination may be appropriate, with the study components selected by the referring or performing physician.
Fig. 2.4 Pulsed Doppler velocity recording.The spectral display of the pulsed wave (PW) Doppler signal is shown with the baseline shifted and velocity scale adjusted to avoid aliasing and to use the full vertical axis to improve measurement accuracy; for example, the signal fits but fills the graphical display. The horizontal time scale is 100 mm/s, which is standard for most Doppler recordings.
Fig. 2.5 Color Doppler with signal aliasing.This color Doppler image of LV outflow in an anteriorly angulated apical 4-chamber view shows signal aliasing adjacent to the septum in the subaortic region. Although this appearance may be due to an asymmetric flow profile, the effects of intercept angle also may be important. Even if the velocity is identical across the outflow tract, compared with the region along the anterior mitral valve leaflet, the region adjacent to the septum the Doppler beam is more parallel to the flow direction. The higher Doppler shift results in signal aliasing. Aliasing at the aortic valve level is expected because the aortic velocity typically exceeds the Nyquist limit at this depth (0.73 m/s in this example).
□ The approach suggested here is based on obtaining all data (imaging and Doppler) for each acoustic window (parasternal, apical, subcostal, and suprasternal) before moving to the next acoustic window; this approach minimizes the time needed to reposition the patient between acoustic windows (Fig. 2.6).
Fig. 2.6 Standard acoustic windows.The positions on the chest wall where ultrasound can reach the cardiac structures without intervening lung or bone include the parasternal, apical, subcostal, and suprasternal notch windows. The parasternal and apical windows typically are optimal with the patient in a steep left lateral position. For the subcostal window, the patient is supine with the knees flexed to relax the abdominal vasculature. For the suprasternal notch window, the patient is supine with the head tilted back and to one side.
□ Some examiners prefer to obtain all the imaging data and then obtain all the Doppler data; this approach allows the Doppler data recording to be tailored to the imaging findings.
□ With any approach, the examiner may need to go back to previous acoustic windows at the end of the examination if additional views or measurements are needed based on abnormal findings.
□ The examination sequence also may need to be modified depending on patient factors (inability to move, bandages, etc.) or the urgency of the examination.
□ Basic measurements are made as the examination is performed (Table 2.2) or during review of images at completion of the study. Normal values for chamber sizes are provided in Chapter 6 (Tables 6.2 and 6.3) and for the aorta in Chapter 16 (Tables 16.1 and 16.2).

Step 6: Parasternal Window

Long-Axis View

▪ Many echocardiographers start with the parasternal long-axis view with:
- ○ Imaging to show the aortic and mitral valves, left atrium, aortic sinuses and ascending aorta, LV basal segments, and the right ventricular (RV) outflow tract
- ○ Color Doppler to screen for aortic and mitral regurgitation
▪ Standard measurements include:
- ○ LV end-diastolic and end-systolic diameters; diastolic thickness of the septum and LV inferior-lateral wall just apical from the mitral leaflet tips (Fig. 2.7)
- ○ Aortic diameter at end-diastole (Fig. 2.8)
- ○ Left atrial anterior–posterior dimension
- ○ Vena contracta width for aortic and mitral regurgitation

TABLE 2.2

Basic Echo Imaging Measurements
Cardiac Structure	Basic Measurements	Additional Measurements	Technical Details
Left ventricle	• ED dimension • ES dimension • Wall thickness • ED volume • ES volume • Ejection fraction	• Stroke volume • LV mass • Global longitudinal strain	• 2D imaging is used to ensure measurements are centered and perpendicular to the long axis of the LV. • M-mode provides superior time resolution and more accurate identification of endocardial borders. • LV volumes and ejection fraction are measured by 2D and 3D imaging. • LV volumes and stroke volume often are indexed to body size.
Left atrium	• AP diameter	• LA area • LA volume	• Left atrial anterior–posterior dimension provides a quick screen but may underestimate LA size. • When LA size is important for clinical decision making, measurement of LA volume is helpful.
Right ventricle	• Visual estimate of size • TAPSE	• ED RV outflow tract diameter • ED RV length and diameter	• Quantitation of RV size by echo is challenging due to the complex 3D shape of the chamber. • TAPSE via M-mode is a quantitative measure of RV systolic function.
Right atrium	• Visual estimate of size		• RA size is usually compared to the LA in the apical 4-chamber view.
Aorta	• ED diameter at sinuses	• Maximum diameter indexed to expected dimension • Diameter at multiple sites in aorta	• With 2D echo, inner edge to inner edge measurements are more reproducible. • Measurements are made at end-diastole by convention, but end-systolic measurements also may be helpful.
Pulmonary artery		• Diameter

Key Points

□ Images are initially recorded at a depth that includes the descending thoracic aorta to detect pleural and pericardial effusions.
□ Next, depth is reduced to the level of the posterior wall for assessment of the size and function of the base of the LV basal segments and the RV outflow tract.
□ The aortic and mitral valves are examined with zoom mode sweeping through the valve planes from medial to lateral to assess valve anatomy and motion (Fig. 2.9).
□ M-mode tracings of the mitral valve can aid in timing of leaflet motion, such as systolic anterior motion in hypertrophic cardiomyopathy or posterior buckling in mitral valve prolapse.
□ Left atrium (LA) anterior–posterior dimension may underestimate LA enlargement; LA volume is measured from apical views.
□ The aortic sinuses of Valsalva and sinotubular junction are visualized first from the standard window and then with the transducer moved up one or more interspaces to visualize the proximal and mid-ascending aorta (Fig. 2.10).
□ Color Doppler of aortic and mitral valves is used to screen for valve regurgitation. If more than physiologic regurgitation is present, further evaluation is needed as discussed in Chapter 12.

Right Ventricular Inflow View

▪ From the long-axis view, the image plane is angled medially to show the RV inflow view (Fig. 2.11) with:
▪ Standard measurements include:
- ○ Maximum tricuspid regurgitant velocity (Fig. 2.12)

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Tags: Echocardiography Review Guide

Apr 23, 2020 | Posted by admin in CARDIOLOGY | Comments Off

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Thoracic Key

Fastest Thoracic Insight Engine

The Transthoracic Echocardiogram

The Transthoracic Echocardiogram

Step-By-Step Approach

Step 1: Clinical Data

Step 2: Patient Positioning

Step 3: Instrumentation Principles

Step 4: Data Recording

Step 5: Examination Sequence

Step 6: Parasternal Window

Long-Axis View

Right Ventricular Inflow View

Full access? Get Clinical Tree

Thoracic Key

Fastest Thoracic Insight Engine

The Transthoracic Echocardiogram

Step-By-Step Approach

Step 1: Clinical Data

Key Points

Step 2: Patient Positioning

Key Points

Step 3: Instrumentation Principles

Key Points

Step 4: Data Recording

Key Points

Step 5: Examination Sequence

Key Points

Step 6: Parasternal Window

Long-Axis View

Key Points

Right Ventricular Inflow View

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