Explaining Echocardiography and the Transthoracic Echocardiogram

Transthorasic EchocadiogramSince starting the Echocardiography program at the Academy of Ultrasound, LLC, we are constantly looking for new and improved reference materials.  The hope is to better explain, to our students and patients, what we as sonographers do and what the ultrasound test is.

One of the spots we frequent is the Family Practice Notebook (www.fpnotebook.com).  Recently we found a new outline formatted description of an Echocardiogram.  Its a great synopsis, complete with references to common terms and images. 

Below is their description.  Review it and leave any comments you might have.  We feel it will help with your understanding of the basic Echocardiography exam.

If you like it be sure to share this with your friends.

 

 

 Transthoracic Echocardiogram

See Also

    1. Transesophageal Echocardiogram
    2. Echocardiogram in Congestive Heart Failure
    3. Stress Echocardiogram
  • Background
    1. Use Phased-Array transducer (1-5 MHz)
      1. Faster frame rate to catch dynamic images throughout cardiac cycle
      2. Use cardiac preset
        1. Transducer marker corresponds to screen right (contrast with other presets where marker is on screen left)
    2. Most patients will have one adequate view to visualize heart function
      1. Quality of view is inversely proportional to body habitus (i.e. Obesity degrades the view)
      2. However, technique for a single view can be modified to visualize most structures
    3. Emergency Echocardiography (or Focused UltrasoundExamination) does not replace a complete Echocardiogram
      1. Emergency Echocardiogram is done to answer specific emergency related questions
  • Precautions
    1. Pericardial Effusion
      1. Features
        1. Pericardial Effusion will surround the heart and should be seen in multiple views
        2. Pericardial fluid moves in opposite direction as heart wall
        3. Cardiac Tamponade
          1. Right heart wall movement will be paradoxical rocking motion
            1. Right atrium collapse in systole (also occurs with hypovolemic shock)
            2. Right ventricular collapse in diastole
      2. Differential diagnosis (look-alikes on Echocardiogram, confirm in multiple views)
        1. Pericardial fat pad (moves with heart wall)
        2. Descending aorta
  • Indications: Emergency Echocardiogram
    1. Cardiac Arrest
      1. Cardiac standstill
        1. Distinguish from Ventricular Fibrillation appearance (shimmering appearance of ventricular wall)
        2. Distinguish from lung excursion with Positive Pressure Ventilation (stop PPV to visualize heart activity)
        3. Prolonged cardiac standstill may demonstrate congealed blood in ventricle
        4. Associated with little to no chance of survival (helps direct cessation of code)
          1. Blaivas (2001) Acad Emerg Med 8:616
      2. Identify reversible causes of PEA
        1. Cardiac Tamponade (Pericardial Effusion and right ventricular collapse in diastole)
        2. Hypovolemic shock (hyperdynamic heart with with small ventricular chamber)
        3. Pulmonary Embolism (new dilated right ventricular chamber)
        4. Myocardial Infarction (new wall motion abnormality, decreased contractility or EF)
    2. Shock or Hypotension
    3. Acute Dyspnea
    4. Trauma
      1. See FAST Exam
    5. Myocardial Infarction
    6. Ultrasound-Guided Pericardiocentesis
  • Views: General
    1. Parasternal Echocardiogram View
      1. Parasternal Long-Axis Echocardiogram View
      2. Parasternal Short-Axis Echocardiogram View
    2. Apical Echocardiogram View
    3. Subcostal Echocardiogram View
    4. Suprasternal Echocardiogram View
  • Views: Parasternal Long-Axis Echocardiogram View
    1. Improved window (bring heart closer to transducer and reduce rib shadowing)
      1. Patient positioned in left lateral decubitus position
      2. Start along sternal border near the 3rd interspace and check several interspaces inferiorly and laterally
    2. Transducer orientation
      1. Transducer 3-5 cm to the left of the left sternal border at the 3rd to 5th intercostal space
      2. Transducer indicator pointed towards patient’s right Shoulder (10:00 position)
    3. Images
      1. UltrasoundHeartPLAXAndPSAX.jpg
    4. Landmarks
      1. Right ventricle or right ventricular outflow tract
      2. Left ventricle, aortic valve and proximal aorta
      3. Mitral valve and left atrium
      4. Descending Aorta
    5. Conditions
      1. Visualizes the positions of the parasternal short axis cross sections (see below)
      2. Wall motion abnormalities (especially apex and septum)
      3. Valvular insufficiency (Mitral Regurgitation or Aortic Insufficiency) with color doppler
      4. Aortic root dilation (best imaged with same probe orientation but at the 3rd intercostal space)
      5. Left ventricular Systolic Dysfunction(CHF)
        1. Decreased contractility of left ventricle
          1. Normal
          2. Depressed or severely depressed
          3. Hyperdynamic
        2. Decreased ejection fraction
          1. Gross Estimate
            1. Estimate visually what percentage difference is seen between the left ventricle volume in systole and diastole
            2. M-mode compare end-systolic (ESD) and end-diastolic (EDD) diameters
          2. Linear calculation: Ultrasoundcalc package
            1. In M-Mode, measure end-diastolic (EDD) and end systolic (ESD) diameters
            2. Ejection fraction = 100 * (EDD^3 – ESD^3) / EDD^3
        3. Dilated left ventricle (end diastolic diameter >56 mm)
          1. Measure across widest point between septum and posterior wall
          2. Chordae tendinae may obscure true posterior wall
        4. E-point septal separation (EPSS) on M-Mode or cine
          1. Distance between the septum and the mitral valve leaflet when maximally open
          2. Normal is <8-10 mm (>20 mm is correlated with an EF<30%)
  • Views: Parasternal Short-Axis Echocardiogram View
    1. Transducer orientation (start)
      1. Transducer Rotated 90 degrees clockwise from Parasternal Long Axis View
      2. Transducer 3-5 cm to the left of the left sternal border at 3rd to 5th intercostal space
      3. Transducer indicator pointed towards patient’s left Shoulder (1:00 position)
    2. Transducer gradually tilted down heart axis to obtain 4 heart cross-sectional slices
      1. Aortic valve level
      2. Mitral valve level
      3. Mid-ventricle level
      4. Heart apex
    3. Images
      1. UltrasoundHeartPLAXAndPSAX.jpg
    4. Landmarks: Aortic valve level
      1. Right ventricular outflow tract
      2. Tricuspid valve, aortic valve (peace or mercedes sign when tri-leaflet) and pulmonic valve
      3. Right atrium, left atrium and pulmonary artery
    5. Landmarks: Mitral valve level
      1. Right ventricle
      2. Mitral valve (anterior and posterior leaflets appear as a fish mouth opening and closing)
    6. Landmarks: Mid-ventricle level
      1. Right ventricle
      2. Left ventricle (with trabeculations representing papillary muscles)
    7. Landmarks: Apical level
      1. Right ventricle (much smaller in size than left ventricle unless right ventricle dilated)
      2. Left ventricle
    8. Conditions
      1. Bicuspid aortic valve (Aortic valve level)
      2. Left ventricle wall motion abnormality (mid-ventricle level)
        1. Best view to see all left ventricle walls
  • Views: Apical Four Chamber Echocardiogram View
    1. Transducer orientation
      1. Transducer placed at PMI or approximately xiphoid level (6th intercostal space) in mid-clavicular line or nipple line
      2. Transducer indicator pointed towards patient’s left (3:00 position)
      3. Align energy toward right Shoulder along heart’s long axis
      4. Hand holding transducer is pushed with knuckles into the bed to get best angle through heart
    2. Landmarks: Four chamber heart view
      1. Right ventricle and left ventricle
      2. Tricuspid valve and mitral valve
      3. Right atrium, left atrium and descending aorta
    3. Conditions
      1. Pericardial Effusion
      2. Apical thrombus (decrease depth to see, apex is closest to probe in this location)
      3. Systolic Dysfunction
      4. Wall motion abnormalities
  • Views: Subcostal Echocardiogram View (or subxiphoid view)
    1. See FAST Exam
    2. Pearls to improve view window
      1. Consider starting this view longitudinally with indicator at 12:00 to identify left lobe of liver and angle through heart
      2. View improves with the patient taking a deep inspiration
    3. Transducer orientation
      1. Hold transducer over the top (more at the base of probe) to allow for a more shallow angle
      2. Push the transducer down (posteriorly) to drop below (deep) to the xiphoid process
      3. Transducer placed sub-xiphoid (by 1-2 cm) in superior epigastrium
      4. Transducer indicator pointed towards patient’s right (9-10:00 position) with energy toward left Shoulder
    4. Landmarks
      1. Four chamber heart view
      2. Increase angle of approach (aiming more posterior) if aorta is seen in the four chamber view
    5. Conditions
      1. Pericardial Effusion
      2. Systolic Dysfunction
      3. Wall motion abnormalities
  • Views: Subcostal Longitudinal (volume status view)
    1. Pearls to improve view window
      1. View improves with the patient taking a deep inspiration
    2. Transducer orientation
      1. Transducer placed right lateral to sub-xiphoid
      2. Transducer indicator pointed towards 12:00 with energy toward left atrium
    3. Landmarks
      1. Inferior vena cava
      2. Right atrium
    4. Conditions
      1. Volume depleted (e.g. Hemorrhagic Shock, dehydration)
      2. Volume overload (e.g. Congestive Heart Failure)
    5. Interpretation: Volume status based on IVC alone
      1. Inferior vena cava (IVC) is normally 1.5 to 2.5 cm in diameter (measured 3 cm from atrium)
        1. IVC <1.5 cm suggests volume depletion
        2. IVC >2.5 cm suggests volume overload
      2. Inferior vena cava (IVC) normally collapses more than 50% with inspiration or sniffing
        1. Total collapse suggests volume depletion
        2. Collapse <50% suggests volume overload
      3. Correlation between RA pressure (CVP) and IVC appearance
        1. CVP 0-5 cm: IVC totally collapses on inspiration and is <1.5 cm in diameter
        2. CVP 5-10 cm: IVC collapses >50% on inspiration and is 1.5 to 2.5 cm in diameter
        3. CVP 11-15 cm: IVC collapses <50% on inspiration and is 1.5 to 2.5 cm in diameter
        4. CVP 16-20 cm: IVC collapses <50% on inspiration and is >2.5 cm in diameter
        5. CVP >20 cm: No change in IVC on inspiration and is >2.5 cm in diameter
    6. Interpretation: Volume status by Caval Aorta Index
      1. Step 1: Measure maximal internal IVC anteroposterior diameter (in M Mode)
        1. Subxiphoid level in longitudinal axis
        2. Measure just caudal to confluence of hepatic veins
      2. Step 2: Measure maximal internal aorta anteroposterior diameter (in M Mode)
        1. Subxiphoid region in longitudinal axis
        2. Measure just to the left of the IVC
      3. Step 3: Calculate the Caval Aorta Index as IVC/Ao
        1. CVP <7 cm H2O: Caval Aorta Index of 0.72 (+/- 0.09)
        2. CVP 8-12 cm H2O: Caval Aorta Index of 1.23 (+/- 0.12)
        3. CVP >13 cm H2O: Caval Aorta Index of 1.59 (+/- 0.05)
      4. Reference
        1. Sridhar (2012) ISRN Emergency
  • Views: Suprasternal Echocardiogram View
    1. Transducer orientation
      1. Transducer placed in suprasternal notch
      2. Transducer indicator pointed towards 9:00
      3. Align energy inferiorly (towards feet) until arch comes into view
      4. Rotate transducer clockwise until arch is in full view
    2. Landmarks
      1. Brachiocephalic artery, Left Carotid Artery, Left subclavian artery
      2. Aortic arch
      3. Right pulmonary artery
      4. Left atrium
    3. Conditions
      1. Aortic Dissection
      2. Aortic aneurysm
  • Resources
    1. Sub-xiphoid View Video (SonoSite)
      1. http://www.youtube.com/watch?v=1UJ6RodOSTw
    2. Apical 4-Chamber View Video (SonoSite)
      1. http://www.youtube.com/watch?v=_eHZz-OCc_M
    3. Parasternal Long Axis View Video (Sonosite)
      1. http://www.youtube.com/watch?v=4qerzEW_ASU
    4. Parasternal Short Axis View Video (SonoSite)
      1. http://www.youtube.com/watch?v=EaLuCBXXINg
    5. Suprasternal Notch View Video (Sonosite)
      1. http://www.youtube.com/watch?v=Mkc6tUVRgKo
    6. Inferior Vena Cava UltrasoundVideo (SonoSite)
      1. http://www.youtube.com/watch?v=ci9W4MvyMHI
    7. Echocardiographer
      1. http://echocardiographer.org/
  • References
    1. Mateer and Jorgensen (2012) Introduction and Advanced Emergency Medicine Ultrasound Conference, GulfCoast Ultrasound, St. Pete’s Beach
    2. Noble (2011) Emergency and Critical Care Ultrasound, Cambridge University Press, New York, p. 61-88
    3. Reardon (2011) Pocket Atlas Emergency Ultrasound, McGraw Hill, New York, p. 61-106

By John Sheldon