Echocardiography Basics

Echo

The Emergency Echo

PDF HANDOUT – Click Here

A Review of the Essentials of Ultrasound

  • Ultrasound (USS) at the point of care is becoming an increasingly important skill for critical care practitioners
  • Cardiac USS, or Echocardiography, is becoming increasingly accessible at the point of care delivery due to extraordinary advanced in technology in the last 10 years
  • The cost of a reasonable USS with Echo capability now costs about the same as motorbike whereas 15 years ago it was the cost of a house…

Echo For Dummies

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Point of Care USS and Echocardiography

  • Pros include:
    • Non-invasive and Real Time
    • A Reproducible and Repeatable Exam
    • Multiple advantages over Clinical Examination (many of us have experience the limits of auscultation)
    • Relatively Fast to complete a limited study – complements a formal departmental Echocardiogram
    • Quantifiable Haemodynamic Information
  • Cons include:
    • Study limited by operator skill, equipment and patient factors
    • Controversy of credentialing, training and skill maintenance

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Screen Shot 2014-05-27 at 11.07.33 AM

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USS Basics

The Machine

  • Modern point of care machines such as General Electric, Phillips and the Sonosite (shown below) have a high degree of functionality for a number of Point of Care studies
  • The USS transducer contains a piezoelectric crystal. This crystal (element) produces the ultrasound beam which penetrates and reflects back.  The USS element has a special property that allows transformation of electrical signals into mechanical energy or mechanical energy into electrical signals.  
  • Most USS waves are absorbed but some waves are reflected especially at interfaces of tissues with varying densities.
  • As a result of these properties an USS image can be created on the screen using advanced (and now very fast) computer software.

A variety of Modes are available to help with image interpretation in the Echocardiogram including:

  • B mode (Brightness Mode)

The most familiar setting seen on the USS machine

      • Press “2D” on the Sonosite Machine to start this mode
      • Displays a 2D cross-sectional image of the tissue under the probe
      • In B mode there is scaling so that the amount of reflection is reflected by the proportional brightness of the displayed dot
      • A detector array allows a real time image to be displayed at > than 30 frames per second
  • A mode (Amplitude Mode)
      • Rarely used in practice – USS is displayed as graph of vertical deflection against time
  • M mode (Motion Mode)
      • Like B mode uses Grey Scale
      • M mode is used to display moving structures for comparison over a set time period
Berhold Block's Comparison of USS Modes
Berhold Block’s Comparison of USS Modes

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  • Pulse Wave (PW)
      • Denoted as “PW” on most machines – allows for measurement of local velocity movements at a specified depth in the examined tissue
      • Localised shifting in the frequency of the USS wave reflects underlying blood flow velocity
      • As a result ‘Pulse Wave’ can be measured and displayed and is widely used in Echo
  • Colour Flow Mapping (CW) 
      • Colour Mode uses measurements of the velocity and direction of liquid (blood) flow to place a real time a colour pattern on top of the B mode image
      • This can be used to examine dynamic flow
      • Flow is remembered by “B A R T” – ‘Blue Away and Red Towards’

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  • The USS machine can produce a variety of real-time images and software allows for freezing images, on screen comparison, measurement and calculations
  • Most Echo capable machines allow on screen ECG to aid with interpretation of the cardiac cycle:

The Sonosite Machine with ECG monitoring

Controls

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Sonosite Control Panel

Screen Shot 2014-05-27 at 11.32.07 AM

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More reading

Further reading on Basic USS and Echo can be found here:

“ACEM College Basic Ultrasound PDF

Cardiology Explained – Echo

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The USS Probe

  • These probes have a variety of different frequencies reflecting their penetration and image detail.
  • In the case of Transthoracic Echo we use a curved linear probe with a small “foot print”:
Cardiac Transducer
Cardiac Transducer

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Orientation

  • Generally USS is carried out in a standard (international) fashion – orientation is an important starting point when doing a bedside point of care USS study
  • In most bedside USS studies we line up the DOT on the probe with the DOT on the screen 
  • This can be easily tested by applying gentle digital pressure to the probe
  • Most USS scans have the dot on the screen lined up with the RIGHT side of the patient or in the vertical plane pointing towards the PATIENT’S HEAD
  • Echo is different to the standard orientation – this can be very confusing initially

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Movements of the Probe

  • There are 4 movements of the probe:
      • TRANSLATION
      • ANGULATION (often referred to as cephlad or caudal – toward the head and feet respectively)
      • ROTATION
      • TILT (commonly known as Heel-Toe)

Here is a Video we have edited showing these movements:

  • Movements should be very slow and subtle – in any USS scan it is easy to gain and lose your image very easily with over vigorous movements of the probe
  • Generally we hold the probe firmly but not in a vice like manner
  • 3 or 4 fingers should be holding the probe with 1 or 2 fingers on the patient for support and improved control

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Position of the Examiner

  • For all Echo studies use your left hand to move the probe (with support from your free right hand if required)
  • Sit on the patient’s left side so you can easily adjust the machine with your free right hand

Echo - IHEARTSCAN POSITION

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The Echo Images

  • The main Transthoracic Echocardiography (TTE) windows are:
    • Parasternal
    • Apical
    • Subcostal
  • Alternative views including supraclavicular are sometimes used for TTE
Standard TTE Views
Standard TTE Views

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Stepwise Approach

Parasternal Views

  1. Parasternal Long Axis (PLAX) – probe is on the left sternal edge and probe marker (dot) is pointed towards the right shoulder – dot on the screen (as always in TTE preset) is on the right of the screen.
  2. Patient should be leaning towards their left side
  3. Key
    • P = Pericardium
    • FW = Free Wall
    • IVS = Intra-ventricular Septum
    • A = Aortic Valve
    • M = Mitral Valve
    • LV = Left Ventricle
    • RV = Right Ventricle
    • LA = Left Atrium
    • DA = Descending Aorta
PLAX - Sketch of Anatomy
PLAX – Sketch of Anatomy
PLAX Probe Position
PLAX Probe Position

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    • Parasternal Short Axis View (PSAX) – This window is obtained by rotating the probe clockwise 90 degrees to the marker on the probe points to the left shoulder
    • The probe is then angulated (towards the head and then towards the feet) – to obtain various short axis cuts through the heart that I have crudely illustrated below.  This view allows for further measurements of ventricular function, valve function and dimensions of various structures.
      • Key
        • A = Anterior Mitral Valve Leaflet 
        • P = Posterior Mitral Valve Leaflet 
        • PV = Pulmonary Valve
        • TV = Tricuspid Valve
        • MB = Moderator Band (part of RV)
        • I = Inferior Wall Left Ventricle
        • S = Septal Wall Left Ventricle
        • AS = Antero-septal Wall Left Ventricle
        • A = Anterior Wall Left Ventricle
        • L = Lateral Wall Left Ventricle
        • PAP = Papillary Muscle
PSAX - Superior View (USS Beam Angulated towards head)
PSAX – Superior View (USS Beam Angulated towards head)
PSAX - Mitral Valve View (USS Beam Angulated towards feet)
PSAX – Mitral Valve View (USS Beam Angulated towards feet)
PSAX - PAP Muscle Level (USS Beam Angulated towards feet)
PSAX – PAP Muscle Level (USS Beam Angulated towards feet)

EchoBasics has beautiful pictures of normal echo with simplified anatomical labelling:

Click Here

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Apical Views

  • Apical View – place the probe at the apex with the marker facing the bed:
    • 4 Chamber
    • 4 Chamber (inferior with coronary sinus)
    • 5 Chamber
  • Rotate 90 degrees anticlockwise
    • 2 Chamber
  • Rotate a further 10-15 degrees
    • 3 Chamber (apical long axis)

Apical 4 Chamber 

4 Chamber

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Apical 5 Chamber 

5 Chamber

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Apical 2 Chamber 

IMG_20140527_095958

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Apical 3 Chamber (long axis) 

IMG_20140527_100336

Subcostal Views

  • The probe is placed below the sternum with an overhand grip pointing toward the left shoulder.  We use the liver as an acoustic window.  Downward pressures is typical applied on the probe and respiration will change the view obtained.  Views at this window include:
    • 4 Chamber
    • Short Axis views (parallel to the Parasternal Short Axis views described above)
    • Views of the Inferior Vena Cava
    • Views of the Descending Aorta

Subcostal 4 Chamber View

IMG_20140527_100652

IVC Ultrasound

 

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Conclusion

In this post we have covered the fundamentals of bedside point of care USS imaging and covered how to obtain the basic views for an Echocardiogram in the Emergency Department.

 The key to success with any bedside study is to practice and learn from your skilled colleagues, textbooks and the FOAM community online.

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Ultrasound Resources

  1. EchoBasics

  2. Phillips

  3. Sonosite

  4. PUB MED Review

  5. ACEM USS

 


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