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Tutorial 3 - Setting up and acquiring images

SETTING UP AND ACQUIRING IMAGES

 

Optimal positioning for most echo examinations is the left lateral position. A small subset of patients may have good visualization of the apical 4 and 5 chamber views in supine position. The subcostal view requires the patient to be in supine position.

The examination can be done from the right or left side of the patient. People in different centers have different preferences. However, from the point of view of infection control in the ICU, it is better for the examiner to stand on the left of the patient as this reduces direct contact with the patient. This would mean handling the probe with the left hand and operating the knobs on the machine with the right.


  • Adjust the height of the patient bed for your comfort. Keep the machine close so your other non-probe hand can operate controls.

  • Connect the ECG cables of the Echo machine.

  • Dim the lights.

  • Use adequate ultrasound jelly on the probe. It may be better to use separate sachets of jelly for each patient.

  • 2-D:
    Adjust the overall gain knob till the picture is neither too dark nor too bright.

  • Adjust the time-gain control (a series of sliders arranged in a row) so that the picture has uniform brightness from top to bottom.

  • Use depth knob to set the minimum depth required. The main structure of interest should be in the center of the screen.

  • Doppler:
    CFI- Turn up colour gain till speckling occurs in tissues (speckling indicates too much gain), then turn it down until the speckling disappears (correct gain).

  • PWD and CWD:
    Adjust baseline and scale to so that the entire waveform is seen.

  • Measurement:
    All machines have caliper and trace functions either with a trackball or a touch pad, which allow measurement of distance, time and areas. These form the basis of most of the hemodynamics calculations such as velocities, gradients, areas and size. More sophisticated machines have automated measurement devices and a bewildering array of calculation options.



VIEWS


It is useful to visualize the heart as being transected by three main axes of imaging.


Three Orthogonal Planes:

  • Long Axis - transects the heart from aortic root to the left ventricular apex

  • Short Axis - runs from left mid clavicle to the right hip

  • Four Chamber Axis - runs from apex to the base; perpendicular to other 2 axes



Parasternal long axis view (PLAX)


Transducer position: left sternal edge; 2nd to 4th intercostal space.

Marker dot direction: points towards right shoulder

Structures seen are illustrated below.

 

Figure 1: Parasternal long axis view: http://www.med.yale.edu/intmed/cardio/echo_atlas/contents/index.htmlFigure 1: Parasternal long axis view: http://www.med.yale.edu/intmed/cardio/echo_atlas/contents/index.html

 

 

 

 

Video 1.  This video shows a normal parasternal long axis view.

The parasternal long axis view is commonly the first view obtained in an echo examination and is useful for assessing contractility visually, calculating ejection fraction in M-mode, detecting regional wall motion abnormalities and measuring LV outflow tract diameter for cardiac output studies.



Parasternal short axis view (PSAX)


Transducer position: left sternal edge; 2nd to 4th intercostal spaces

Marker dot direction: points towards left shoulder (90 degrees clockwise from PLAX view)


Figure 2: Changing the angle of the ultrasound probe results in being able to view short axis images from the aortic root down to the apexFigure 2: Changing the angle of the ultrasound probe results in being able to view short axis images from the aortic root down to the apex



By tilting the transducer on an axis between the left hip and the right shoulder, short-axis views are obtained at different levels, from the aorta to the LV apex. This angulation of the transducer from the base to the apex of the heart for short axis views is known as "breadloafing". Short axis sections are viewed at Aortic root level, mitral valve level and papillary muscle level.

The structures seen are illustrated below.


Figure 3: Short axis view at the level of the papillary muscles: http://www.med.yale.edu/intmed/cardio/echo_atlas/contents/index.htmlFigure 3: Short axis view at the level of the papillary muscles: http://www.med.yale.edu/intmed/cardio/echo_atlas/contents/index.html



Figure 4: Short axis view at the level of the aortic valve: http://www.med.yale.edu/intmed/cardio/echo_atlas/contents/index.htmlFigure 4: Short axis view at the level of the aortic valve: http://www.med.yale.edu/intmed/cardio/echo_atlas/contents/index.html


Video 2. Short axis view at the level of the AV valve



Video 3. Short axis view at the level of the mitral valve



Video 4.  Short axis view at the level of the papillary muscles

The parasternal short axis view at the level of the aortic valve is used to look for vegetations, and other abnormalities of aortic valve structure.

The parasternal short axis view at the level of the mitral valve is used to measure mitral valve area.

 The parasternal short axis view at the papillary muscle level is useful for assessing the LV end diastolic area (an index of volume status), visual gestalt assessment of contractility, detecting regional wall motion abnormalities, detecting right ventricular enlargement and assessing interventricular septum motion abnormalities in acute cor pulmonale.


Apical 4 chamber view (A4C)


Transducer position: apex of the heart

Marker dot direction: points towards left shoulder

Structures seen are illustrated below.


Figure 5: Apical 4 chamber view: http://www.med.yale.edu/intmed/cardio/echo_atlas/contents/index.htmlFigure 5: Apical 4 chamber view: http://www.med.yale.edu/intmed/cardio/echo_atlas/contents/index.html





Video 5. Apical 4 chambered view. note the pulmonary veins entering the left atrium

The apical 4 chambered view is used to detect and quantify mitral and tricuspid regurgitant and stenotic lesions using color flow imaging and Doppler. It is also used to detect right ventricular enlargement, visually assess RV and LV contractility, calculate ejection fraction using the 2D method, assess mitral and tricuspid inflow patterns and measure pulmonary vein inflow for diastolic function .


Apical 5 chamber view (A5C)


Transducer position and marker dot direction are same as the A4C view. The A5C view is obtained from the A4C by slight anterior angulation of the transducer towards the chest wall. The 5th chamber added is the LVOT.



Figure 6: Figure 6: Apical 5 chamber view – the LVOT, aortic valve and root are visualizedFigure 6: Figure 6: Apical 5 chamber view – the LVOT, aortic valve and root are visualized





Video 6.  The LVOT has been opened up to show the apical 5 chambered view

The apical 5 chambered view is used to measure LV ouflow tract velocities to measure cardiac output. It is also useful to detect and quantify aortic regurgitation and stenosis using color flow imaging and Doppler.


Apical 2 chamber view (A2C)


Transducer position: apex of the heart

Marker dot direction: points towards left side of the neck (45 degrees anti-clockwise from A4C view)

Structures seen are illustrated below


Figure 7: Apical 2 chamber view: http://www.med.yale.edu/intmed/cardio/echo_atlas/contents/index.htmlFigure 7: Apical 2 chamber view: http://www.med.yale.edu/intmed/cardio/echo_atlas/contents/index.html






Video 7.  Apical 2 chambered view. Note the left atrial appendage appearing as a cul-de-sac towards the right, and the coronary sinus, seen in cross section to the left of the atrioventricular junction

The apical 2 chambered view is used to measure ejection fraction using the Simpson's method. It is also useful to visualize the left atrial appendage to look for a thrombus. Mitral regurgitation jets may sometimes be seen better in this view than in the A4C.


Apical long axis or 3 chamber view (A3C)


Transducer position: apex of the heart

The transducer is placed at the same position as for a A4C view and then turned clockwise by 60°.

Structures visualized: It is similar to a parasternal long axis view seen from the apex and characterized by the presence of the mitral and aortic valves in the same plane.


Video 8.   Apical 3 chambered view

The apical 3 chambered view is used to measure LV outflow tract velocities when the A5C is suboptimal.


Subcostal view


The patient should ideally be placed in a supine position for a subcostal view examination. The abdomen has to be relaxed to allow indentation of the probe into the epigastrium.

Transducer position: under the xiphisternum

Marker dot direction: points towards left shoulder


Figure 8: Probe position for the subcostal view: http://www.hcmcem.com/frmain.htmFigure 8: Probe position for the subcostal view: http://www.hcmcem.com/frmain.htm



The structures seen are illustrated below.


Figure 9: Subcostal 4 chamber view: http://www.med.yale.edu/intmed/cardio/echo_atlas/contents/index.htmlFigure 9: Subcostal 4 chamber view: http://www.med.yale.edu/intmed/cardio/echo_atlas/contents/index.html




The inferior venacava (IVC), descending aorta, interatrial septum and pericardial effusions are best seen in this view. This view is also particularly useful when obesity, emphysema or chest wall deformity prevents satisfactory transthoracic views from being obtained.

It is used to measure IVC variability to assess volume status, diagnose small pericardial effusions, measure RV free wall thickness to diagnose chronic cor pulmonale.

 

 

Video 9. A demonstrative lecture on probe positions for various views from the Indira Gandhi National Open University's Youtube channel

Note: This is a large video file and may take time to download. Pause play back for a couple of minutes at the start of the video and then play it. This will help prevent interrupted playback on slow connections

Video 10. A demonstrative lecture on structures to be evaluated for various
views from the Indira Gandhi National Open University's Youtube channel

Note: This is a large video file and may take time to download.
Pause play back for a couple of minutes at the start of the video and
then play it. This will help prevent interrupted playback on slow
connections

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