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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.
- 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
- 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 HASH(0x2fd0288) 35%
- Mitral regurgitation, effective regurgitant orifice area (ERO)
- Severe regurgitation: ERO HASH(0x2fcfe80) 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: HASH(0x2fcfe80) 1.5 cm2
- Tricuspid annular plane systolic excursion (TAPSE) reflecting right ventricular function
- Reference value HASH(0x2fcfe80) 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.