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JanneRapola

Echocardiography as an Outpatient Procedure

Essentials

  • Echocardiography (ultrasound examination of the heart, ECHO, UCG) has a central role as a non-invasive heart examination that can be performed in outpatient care.
  • It gives a comprehensive picture of the heart's structure and function.
  • Echocardiography is performed at the office of a cardiologist, other physician familiar with the method or a sonographer (ultrasound nurse) and requires no preparation.
  • Echocardiography gives a good idea of the contraction (systolic function), relaxation (diastolic function) and structure of the heart.
  • It is the first-line examination in the diagnosis and follow-up of valvular diseases.
  • This article discusses only transthoracic echocardiography (TTE) in adults.

Indications

  • The main indications for echocardiography include
    • investigation of murmurs
    • investigation of symptoms suspected of being of cardiac origin, such as dyspnoea or chest pain
    • diagnosis, grading and follow-up of valvular diseases
    • diagnosis of heart failure (systolic/diastolic / filling pressure)
    • diagnosis of cardiomyopathies.
  • In addition, echocardiography can be used to investigate
    • the aetiology and prognosis of arrhythmias
    • the differential diagnosis of chest pain
    • the diagnosis of peri- and myocarditis
    • the state of congenital heart defects in adults
    • problems following heart surgery
    • the state of the ascending aorta
    • cardiac effects of the treatment of other diseases (e.g. cytotoxic drugs, radiotherapy)
    • the possibility of cardiac embolism
    • pulmonary arterial pressure.
  • Echocardiography is increasingly used in acute situations, such as acute coronary syndrome (wall motion abnormality), in emergency and critical care settings and in situations involving resuscitation.

Technology of echocardiography

Two-dimensional grey scale imaging (2D imaging)

  • Basic examination quickly providing a general impression of heart structure and function.
  • The image can be used to measure
    • the thickness of the myocardium
    • the size of various parts of the heart (atria, ventricles, ascending aorta, inferior vena cava)
    • pumping function.
  • To assess
    • any structural abnormality
    • the state of the pericardium / pericardial effusion
    • the structure and function of the valves (e.g. calcification, prolapse).

Doppler examinations

  • To study blood flow.
  • Colour Doppler shows the direction and velocity of blood flow and any turbulence.
    • Valvular defects
    • Shunts
  • Pulsed and continuous wave Doppler measure the direction and velocity of blood flow.
    • To determine the severity of valvular defects
  • Tissue Doppler measures the velocity of myocardial motion.
    • Particularly to assess diastolic function

Other ultrasound techniques

  • M-mode ultrasonography, one-dimensional
    • Excellent temporal and spatial resolution but very limited measuring area
  • Strain imaging
    • Measures deformation of the myocardium.
    • The most sensitive method to detect mild or early disturbances in myocardial function
  • 3D (4D) imaging
    • Forms a three-dimensional image of the heart that can be viewed from various directions.
    • A demanding technique that may at best give an anatomical picture of the various heart structures.
  • Exercise echocardiography
    • The effect of stress (induced by a drug or by physical exercise) on myocardial contractility (ischaemia causes wall motion abnormalities) or valve function (functional mitral regurgitation, for example, increases during stress) is followed.
    • This is a demanding technique not widely used everywhere.

Main measurements with reference values

  • Reference values may vary from country to country. Check locally applied values.
  • Left ventricular end-diastolic dimension
    • Reference values
      • Women < 53 mm
      • Men < 59 mm
  • Left ventricular ejection fraction (EF; the share of the total volume of blood in the heart pumped during one beat)
    • Reference value > 55%
      • Slightly reduced 45-54%
      • Moderately reduced 36-44%
      • Severely reduced ≤ 35%
  • Mitral regurgitation, effective regurgitant orifice area (ERO)
    • Severe regurgitation: ERO ≥ 0.40 cm2
    • Moderately severe regurgitation: 0.20-0.39 cm2
    • Mild regurgitation: < 0.20 cm2
  • Aortic stenosis, aortic valve area (AVA)
    • Severe stenosis: AVA < 1.0 cm2
    • Moderately severe stenosis: 1.0-1.4 cm2
    • Mild stenosis: ≥ 1.5 cm2
  • Tricuspid annular plane systolic excursion (TAPSE) reflecting right ventricular function
    • Reference value ≥ 16 mm

Echocardiography in acute situations

  • Acute circulatory failure/shock - differential diagnosis
    • Acute pumping failure, ischaemia, arrhythmia
    • “Valvular catastrophe”
    • Tamponade or other external compression
    • Hypovolaemia (haemorrhagic shock)
    • Right heart strain/failure (massive pulmonary embolism, right ventricular infarction)
  • Acute chest pain - differential diagnosis
    • Wall motion abnormality suggesting ischaemia
    • Dissection of the ascending aorta
    • Massive pulmonary embolism
    • Myo-/pericarditis
    • Pleural effusion

Limitations of echocardiography

  • Visibility: ultrasound passes bone and air poorly
    • The heart is visible only through certain “windows”.
    • Visibility is restricted by
      • pulmonary emphysema
      • abundant subcutaneous fat
      • very large size of the patient
      • wound dressings, breast implants, other foreign bodies in the area.
  • Coronary arteries are not visible without special techniques, i.e. echocardiography cannot be used to assess the extent and severity of coronary artery stenosis.