Practical Manual of Echocardiography in the Urgent Setting

Vladimir Fridman, Mario Garcia, Vladimir Fridman, Mario Garcia

• Publisher: Wiley
• Year: 2013
• Print ISBN: 9780470659977
• eBook ISBN: 9781118613412
• Edition: 1
• Topic: Medicine
• Subtopic: Cardiology

Practical Manual of Echocardiography in the Urgent Setting

In the acute care setting, medicine happens at full speed and with little margin for error. As echocardiography plays an ever more important role in the diagnosis of patients who present with symptoms that suggest a cardiovascular emergency, clinicians must learn to collect, process and act on echocardiographic information as quickly and effectively as possible.

Practical Manual of Echocardiography in the Urgent Setting covers the essentials of echocardiography in the acute setting, from ultrasound basics to descriptions of all pertinent echocardiographic views to clear, stepwise advice on basic calculations and normal/abnormal ranges.

This compact new reference:

• Provides step-by-step guidance to acquiring the correct views and making the necessary calculations to accurately diagnose cardiac conditions commonly encountered in urgent settings.
• Presents information organized by complaint/initial presentation so that readers can work from this first knowledge of the patient through the steps required to pinpoint a diagnosis.
• Covers echo basics, from sound wave characteristics/properties to common device settings to basic ultrasound formulas
• Includes diagnostic algorithms fitted to address the differential diagnosis in the most commonlyencountered clinical scenarios.

Designed and written by frontline clinicians with extensive experience treating patients, Practical Manual of Echocardiography in the Urgent Setting is the perfect pocket-sized guide for residents in cardiology, emergency medicine, and hospital medicine; trainees in echocardiography; medical students on cardiology or emergency medicine rotations; technicians, nurses, attending physicians—anyone who practices in the urgent setting and who needs reliable guidance on echocardiographic views, data and normal/abnormal ranges to aid rapid diagnosis and decision-making at the point of care.

RELATED TITLES:

Kacharava, et al: Pocket Guide to Echocardiography; ISBN: 978-0-470-67444-4

Sun, et al: Practical Handbook of Echocardiography: 101 Case Studies; ISBN: 978-1-4051-9556-0

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CHAPTER 1

Ultrasound physics

Vladimir Fridman

Cardiovascular Diseases, New York, NY, USA

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Echocardiography is one of the most valuable diagnostic tests for the evaluation of patients with suspected cardiovascular disease in the acute setting. Even though echocardiography has become more widely available, its performance and interpretation require practice and knowledge of the principles of image formation. Although the physical principles and instrumentation of ultrasound can be quiet complex, there are a few basic concepts that every echocardiographer and interpreting physician must understand to maximize the diagnostic utility of this test and avoid misinterpretations. These key concepts are covered in this chapter.

The echocardiogram machine (Figure 1.1) is made up of few distinct components:

1 Monitor

2 CPU (central processing unit), responsible for all functions of the echocardiogram

3 Transducer

4 Keyboard/controls

5 Printer

The control panel of any echocardiogram looks similar to that shown in Figure 1.2a. The panel is shown in more detail in Figures 1.2b–d, with the important controls labeled. Although slight changes in control positions are noted between machines from different companies, all machines have the key controls that are shown in these images.

The panel from above image, is split into three frames, and the important controls are labeled below.

Figure 1.1 Echocardiogram machine.

Figure 1.2 Typical echocardiogram control panel.

Figure 1.3 Echocardiography settings.

The important echocardiographic settings as displayed on the monitor of most ultrasound machines are shown in Figure 1.3. These settings can be changed, as needed, to adjust the image quality.

The different echocardiographic modes that are available, which are described later in this book, are:

• M-mode: a graphic representation of a specific line of interest of a two-dimensional image (Figure 1.4).
• 2D: a two-dimensional view of cardiac structures that can be visualized as time progresses (Figure 1.5).
• Color Doppler: a color representation of blood flow velocities ­superimposed on a two-dimensional image (Figure 1.6).
• CW/PW Doppler: the representation of flow velocities as plotted with time on the x axis and velocity on the y axis (Figure 1.7).
• Tissue Doppler: the measurement of tissue velocities (Figure 1.8).

The controls, as shown in the figures, switch between the different modes of echocardiography. However, before moving on to performing and interpreting echocardiograms, it is necessary to be aware of the physics behind this imaging modality.

Figure 1.4 M-Mode: a graphic representation of a specific line of interest of a two-dimensional image.

Figure 1.5 2D: a two-dimensional view of cardiac structures that can be visualized as time progresses.

Figure 1.6 Color Doppler: a color representation of blood flow velocities superimposed on a two-dimensional image.

Figure 1.7 CW/PW Doppler: the representation of flow velocities as plotted with time on the x axis and velocity on the y axis.

Figure 1.8 Tissue Doppler: the measurement of tissue velocities.

Ultrasound generation

Ultrasound is a cyclic sound pressure waveform whose frequency is greater than the limit of human hearing. This number is generally considered to be 20 kHz, or 20 000 Hz (Hertz). Echocardiography usually relies on sound waves ranging from 2 to 8 MHz. The echocardiograph, or any other medical ultrasound machine, produces these high frequency sound waves using transducers that contain a piezoelectric crystal.

A piezoelectric crystal (such as quartz or titanate cyramics) is a special material that compresses and expands as electricity is applied to it. This compression and expansion generates the ultrasound wave. The rate (frequency) of compression and expansion is based on the current that the ultrasound machine applies to the piezoelectric signal, which in turn is based on the settings the operator has selected on the machine.

An ultrasound wave, as all sound waves, has some basic physical properties (Figure 1.9). These are:

• Cycle – the sum of one compression and one expansion of a sound wave.
• Frequency (f) – the number of cycles per second.
• Wavelength (λ) – the length of one complete cycle of sound.
• Period (p) – the time duration of one cycle.
• Amplitude – the maximum pressure change from baseline of a sound wave.
• Velocity (v) – speed at which sound moves through a specific medium.

Figure 1.9 A sound wave is made up of varying pressure cycles formed by repeating of compression and rarefaction. The distance between similar points in a wave is called the wavelength (λ) [1].

Figure 1.10 A pulse can consist of multiple wavelengths of a sound wave. In this figure, three pulses are shown, each the length of two wavelengths (Reproduced from Case [2], with permis...

Table of contents

• Cover
• Series page
• Title page
• Copyright page
• Contributors
• Preface
• CHAPTER 1: Ultrasound physics
• CHAPTER 2: The transthoracic examination
• CHAPTER 3: Transesophageal echocardiography
• CHAPTER 4: Ventricles
• CHAPTER 5: Left-sided heart valves
• CHAPTER 6: Right-sided heart valves
• CHAPTER 7: Prosthetic heart valves
• CHAPTER 8: The great vessels
• CHAPTER 9: Evaluation of the pericardium
• CHAPTER 10: Specialty echocardiographic examinations
• CHAPTER 11: Common artifacts
• CHAPTER 12: Hypotension and shock
• CHAPTER 13: Chest pain syndrome
• CHAPTER 14: Cardiac causes of syncope and acute neurological events
• CHAPTER 15: Acute dyspnea and heart failure
• CHAPTER 16: Evaluation of a new heart murmur
• CHAPTER 17: Infective endocarditis
• CHAPTER 18: Post-procedural complications
• CHAPTER 19: “Quick echo in the emergency department”: What the EM physician needs to know and do
• Index