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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_5790_Библиотеки_им_академика_М_И_Перельмана.pdf
5.3 Standard Planes and Standardised Course of Examination
165
5.2 Equipment Needs and Specific Considerations
5.2.1 Transducers
Age and size of patients from preterm infants to adolescents – variety of (mostly
sector) transducers necessary to fulfil all imaging requirements:
8–10–12 MHz transducer for good near-field resolution in premature/newborn
infants, in this age also linear transducers can be used.
5–3 MHz transducer for far-field penetration and high-flow velocities in older children/adults.
5.2.2 Standard US Techniques
• M-Mode.
• Two-Dimensional Ultrasound (2DUS).
• Continuous Wave Doppler (CW-Doppler).
• Pulsed Wave Doppler (PW-Doppler).
• Colour Doppler Sonography (CDS).
5.2.3 Patient Position
Ideally transthoracic echocardiography is performed in reclined position with
patient lying left side down – to avoid interference from lung tissue (especially in
older children). A supporting pillow helpful.
For suprasternal views neck has to be hyperextended to gain access.
5.2.4 Sedation
Transthoracic echocardiography is mostly feasible without sedation.
Sometimes sedation is essential to obtain accurate diagnostic information.
5.3 Standard Planes and Standardised
Course of Examination
Three Basic Planes:
• Long-axis plane parallel to major axis of left ventricle (LV).
• Short-axis plane orthogonal to major axis of LV.
• Coronal plane through cardiac apex (four-chamber view).
• Transducer positioned to four echocardiographic windows to obtain planes
(Fig. 5.1):
1. Parasternal area near to sternum in second, third or fourth intercostal space.
2. Region of cardiac apex.
3. Subcostal region.
4. Suprasternal notch.
166
Fig. 5.1 Schematic drawing of typical
transducer positions for echocardiography.
Suprasternal, parasternal, intercostal,
apical and subcostal window, with
respective transducer orientation
5 Basics of Paediatric Echocardiography
Long or short axis plane can be generated in each of these areas. Moreover, additional views are obtained by tilting transducer from right to left, from superior to
inferior, or rotating clockwise and counterclockwise.
Ideally every examination should follow standardised protocol:
1. Define visceral situs, describe relationship between descending aorta and infe-
rior vena cava (IVC).
2. Specify position and morphology of atria.
3. Describe systemic and pulmonary venous return, hepatic veins, continuity of
IVC and interatrial septum (IAS).
4. Assess atrioventricular junction: atrioventricular valves and interventricuar
septum (IVS).
5. Ventriculoarterial junction: origin and course of great vessels.
5.4 Normal 2D Echocardiogram Findings
5.4.1 Parasternal Views
5.4.1.1 Parasternal Long Axis View (Fig. 5.2)
Obtained by applying transducer to second till fourth intercostal space, orienting
plane along major axis of heart – from left hip to right shoulder – right ventricle (RV)
and outflow-tract of LV can be identified.
5.4 Normal 2D Echocardiogram Findings
Fig. 5.2 Long axis view. Part of right
ventricle (RV) seen behind chest wall.
Inflow part of left ventricle (LV) with mitral
valve (MV) as well as outflow tract of LV
with aortic valve (AV) depicted; LA left
atrium
167
RV
LV
AV
MV
LA
In infants thymus seen between thoracic wall and heart-improves visualisation
and enlarges sonographic window.
Next structures: interventricular septum, left ventricle and atrium; inflow portion
of left ventricle with mitral valve, outflow portion with aortic valve and ascending
aorta – visualised in same plane.
5.4.1.2 Parasternal Short Axis Views (Figs. 5.3 and 5.4)
Obtained by rotating transducer 90° clockwise from long axis view. Several short
axis planes can be generated by tilting transducer from apical region inferiorly to
base of heart superiorly. Doing this, cross section of LV and part of RV seen at different anatomic levels: cardiac apex, papillary muscles, mitral valve, heart base with
origin of great vessels.
Leftward angulation of transducer: RV outflow tract and main pulmonary artery
(PA) with its bifurcation visualised.
At base of heart: origin of coronary arteries.
5.4.2 Apical Views
Apical four-chamber view (Fig. 5.5).
Standard apical four-chamber view: transducer applied to cardiac apex, plane
oriented perpendicular to atrial and ventricular septa.
168
Fig. 5.3 Parasternal short axis view at base
of the heart. Aorta (Ao) visualised in cross
section, pulmonary artery (PA) with its
bifurcation seen left to Ao
5 Basics of Paediatric Echocardiography
Ao
PA
Fig. 5.4 Parasternal short axis view – at
level of mitral valve. Left ventricle (LV)
depicted in cross section, with leaflets of
mitral valve appearing as fish mouth (→) in
diastole; RV right ventricle
RV
LV
5.4 Normal 2D Echocardiogram Findings
Fig. 5.5 All four chambers
of the heart – apical
4-chamber view.
Interventricular and interatrial
septum (→) seen. LV left
ventricle, RV right ventricle,
LA left atrium, RA right
atrium
169
RV
RA
LV
LA
All four cardiac chambers, mitral and tricuspid valve, IAS and IVS imaged with
anterior angulation of transducer LV outflow tract and ascending aorta visualised
(“five-chamber view”).
5.4.3 Subcostal Views
5.4.3.1 Sagittal Subcostal View
Transducer placed in subcostal region in sagittal plane: descending aorta visualised
left to IVC.
5.4.3.2 Subcostal Four-Chamber View (Fig. 5.6)
Transducer applied to subcostal region, plane tilted superiorly: all four cardiac
chambers imaged like in apical four-chamber view; especially in newborns and
infants, interatrial septum visualised, especially well also drainage of pulmonary
veins (PV) can be demonstrated.
5.4.4 Suprasternal View (Fig. 5.7)
Transducer placed in suprasternal notch with overextended neck: entire aortic arch
with arising supra-aortic vessels visualised. Right PA imaged in cross section
beneath aortic arch.
170
Fig. 5.6 Interatrial septum (IAS) –
subcostal view. IAS (→) imaged especially
well, RA right atrium, LA left atrium
Fig. 5.7 Aortic arch – suprasternal view.
Entire aortic arch with origin of supra-aortal
vessels (→) imaged, right pulmonary artery
(RPA) seen in cross section beneath aortic
arch
5 Basics of Paediatric Echocardiography
RA
IAS
LA
RPA
• This view particularly helpful for differentiating between left or right aortic arch
and assessing supra-aortic great vessels.
5.5 Other Techniques
5.5.1 M (Motion)-Mode Echocardiography
M-Mode – first US application in cardiac imaging; based on 1D view of heart.
Amplitude and motion recorded in real time.
PP V124
-=
5.5 Other Techniques
171
Today M-Mode generated from 2DUS, imaging plane used to position M-Mode
beam.
Applications of M-Mode in paediatric echocardiography:
• Measurement of cardiac chambers, vessels and cardiac septa.
• LV systolic function (shortening fraction).
• Study of valve motion and interventricular septum.
5.5.2 Doppler Sonography
5.5.2.1 CDS with 2DUS
Demonstrates several aspects of blood flow in heart and great vessels.
Assesses direction of intra- and extracardiac shunts, valvular stenoses and
regurgitations.
5.5.2.2 PW- and CW-Doppler
Used in combination with 2DUS and CDS to measure direction and velocity of
blood flow in cardiac chambers, great vessels or across intra- and extracardiac
shunts.
• Advantage of PW-Doppler: ability to sample blood flow in small specific area.
• Limitation of PW-Doppler: maximum detectable velocity limited. Therefore
CW-Doppler used for quantification of severe stenosis and high flow velocities,
etc.
5.5.2.3 Calculation of Pressure (P) Gradients (P1 Minus P2)
Obtained by measuring peak velocity (V) using modified Bernoulli equation:
2
Severity of stenosis can be estimated, and pressure in right ventricle can be calculated from flow velocity of tricuspid regurgitation or through VSD.
5.5.3 Other Calculations and Functional Parameters
Often used for assessing heart function, usually incorporated into device with cardiac quantification software – equations:
• Assessment of LV systolic function:
– Shortening fraction (SF): M-Mode index of percent change in LV diameter
that occurs with systole.
– Ejection fraction (EF): calculated from percent change in LV cavity area that
occurs with systole.
• Assessment of RV systolic function:
– Tricuspid annular plane systolic excursion (TAPSE): M-Mode index of the
displacement of RV base during systole and diastole.
172
5 Basics of Paediatric Echocardiography
5.6 Special Echocardiographic Techniques
5.6.1 Transoesophageal Echocardiography (TEE)
TEE – semi-invasive procedure (transducer introduced into oesophagus).
Major indications of TEE in children.
• Intraoperative or perioperative echocardiography.
• Exact evaluation of morphology of defects in interatrial septum.
• Guidance of interventional procedures during cardiac catheterisation.
• Limited transthoracic echocardiographic window.
5.6.2 Three-Dimensional (3D) Echocardiography
During last decade computer-based 3D-reconstruction techniques and real-time
3DUS imaging (“4DUS”) have become an additional tool used to calculate ventricular volumes and to assess function.
3D/4DUS may play role in exact tomographic evaluation of complex congenital
anomalies and allows more detailed planning of cardiac surgery in some cases.
5.6.3 Tissue Doppler Imaging (TDI)
New technique using Doppler principles to measure velocity of myocardial
motion:
Most important applications: measurement of left ventricular systolic and diastolic function.
5.6.4 Contrast-Enhanced US
Agitated saline or polygelatine – injected intravenously in order to produce contrast
echoes. Alternatively – if available – “Echovist”® (Bayer-Schering) a first generation US-contrast agent unable to pass lung capillaries.
• Clinical application: detection of right to left shunts.
Other CM currently have no importance in paediatric echocardiography.
5.7 Normal Values
See Tables 5.1 and 5.2.
Most other normal values, especially of dimensions of cardiac chambers, vary
with age and body surface area.
1
Regression equations for calculation of z scores of cardiac structures in a large cohort of healthy
infants, children and adolescents: an echocardiographic study. Pettersen MD, Du W, Skeens ME,
Humes RA (2008) J Am Soc Echocardiogr 21:922–934
1
5.8 Pathologic Findings
173
Table 5.1 Normal values for
functional parameters
Table 5.2 Normal values
of peak Doppler flow rates
Shortening fraction (SF) 28–44 %
Ejection fraction (EF) 55–75 %
Ascending aorta 1.2–1.8 m/s
Descending aorta 0.9–1.1 m/s
Pulmonary artery 0.7–1.1 m/s
Tricuspid valve E-wave: 0.6 m/s, A-wave: 0.4 m/s
Mitral valve E-wave: 0.9 m/s, A-wave 0.5 m/s
Vena cava 0.7 m/s
From Snider AR, Serwer GA, Ritter SB (1997) Echocardiography
in pediatric heart disease. Mosby, St. Louis: Year Book, Inc
5.8 Pathologic Findings
5.8.1 Congenital Heart Defects with Left-to-Right Shunt
5.8.1.1 Atrial Septal Defect (ASD)
The interatrial septum (IAS) is assessed best from subcostal and apical four- chamber
views. Depending on location of defect US plane has to be angulated superiorly or
inferiorly from standard four-chamber view.
IAS is thin, particularly fossa ovalis – may be difficult to distinguish true
defects from artefacts. True defects usually show echogenic margins
(T artefact).
CDS and PW-Doppler demonstrate interatrial left-to-right shunt; hemodynamic
relevance of ASD assessed by demonstrating RV volume overloads with dilatation
of RA and PA.
TEE helpful in doubtful cases.
Common Types of ASD (Fig. 5.8)
Ostium secundum ASD (ASD II):
• Most common type of ASD (~70 %).
• Defect in mid portion of IAS, sometimes multiple defects (multifenestrated IAS).
• Occasionally associated with atrial septal aneurysm.
Patent foramen ovale (PFO):
• In neonates and infants small, flap-like opening with left-to-right shunt in mid
portion of IAS (overlap of septum primum with septum secundum).
• In ~30 % of adults visible (demonstration of right- to-left shunt during valsalva
manoeuvre with contrast-enhanced echocardiography).
Sinus venosus ASD (superior vena cava defect):
• Defect in most superior and posterior part of IAS.
• Usually no septal tissue between defect and posterior atrial wall.
• In most cases, anomalous drainage of one (or more) right PV into RA or superior
vena cava (SVC), sometimes SVC overrides defect.
5.8.1.2 Atrioventricular Septal Defects (AVSD)
AVSD characterised by common atrioventricular (AV) valve with one common or
two separate orifices. Characteristically leaflets of common AV-valve insert at same
174
Fig. 5.8 Atrium septum
defect of secundum type
(ASD II) – apical fourchamber view. CDS
demonstrates interatrial
left-to-right shunt by red
colour signals crossing
interatrial septum. Enlarged
right atrium (RA) and right
ventricle (RV) with straight
course of interventricular
septum indicating volume
overload. LA left atrium
RA
5 Basics of Paediatric Echocardiography
RV
LA
level in ventricles (normally insertion of tricuspid valve more apical than of mitral
valve).
If AV-valve attached to crest of interventricular septum (IVS), shunting only
between RA and LA possible (partial AVSD or ostium primum ASD). AV-valve
regurgitation of different degrees at commissures between leaflets (“clefts”) of common AV-valve always present.
Size of interatrial and interventricular communications and ventricles as well as
morphology of common AV-valve best evaluated in subcostal and apical fourchamber views and in parasternal short axis view.
Degree of AV-valve regurgitation and shunting assessed by CDS and CW-Doppler.
Partial AVSD (Ostium Primum ASD):
• Defect only in lowest part of IAS near AV-valve in subcostal and apical four-
chamber view.
• Left-to-right shunt only at atrial level.
• Variable degree of mitral valve regurgitation.
Complete AVSD (Fig. 5.9):
• Ostium primum ASD and Inlet-VSD in the apical and subcostal four-chamber views.
• Interatrial, interventricular and LV-RA shunt.
• Common AV-valve with mitral and tricuspidal valve regurgitation.
5.8.1.3 Ventricular Septal Defects (VSD)
VSD – most common congenital heart defect. Interventricular septum (IVS) divided
into small upper membranous septum and larger muscular septum. Muscular septum consists of inlet, trabecular and outlet-(infundibular) portion.
Most VSD located in membranous part, often adjacent muscular septum involved
(“perimembranous” VSD).
Muscular and subarterial (infundibular) VSD (below great arteries) less common.