fetal echocardiography

fetal echocardiography

Fetal Echocardiography


• INTRODUCTION• TIMING OF FETAL ECHOCARDIOGRAPHY• EQUIPMENT • LATERALITY OF FETAL BODY AND IMAGE

ORIENTATION• VISCEROATRIAL ARRANGEMENT(SITUS)• CARDIAC POSITION AND AXIS ORIENTATION• SEGMENTAL ANALYSIS• ECHOCARDIOGRAPHIC PROJECTIONS


• Malformations of the heart and arterial trunks are the most common form of congenital anomalies found in humans.


• Prevalence of CHD in live born Indian childTotal CHD at birth 130-

270,000/year Critical CHD (requiring

intervention in infancy): 80,000

Critical CHD receiving treatment is only 3.04%

CHD mortality as a fraction of infant mortality: 3-17%

*Based on available data of CHD prevalence at birth In developed countries and present birth rates in India


• Importance in developing world

Limited resources to treat complex heart problems. Relatively few centres in public sector offering

treatment for complex CHD. Very limited infrastructure for transporting sick

neonates with critical CHDs which are correctable.

Early diagnosis is a solution for this

Antenatal Cardiac Diagnosis


• The incidence of CHD is much higher in the fetal population.

• A good number of fetuses with complex cardiac anomalies succumb in the first trimester itself, even before the cardiac anomaly is suspected;

• some parents opt for termination of pregnancy after the diagnosis is made in the mid-trimester; and some cardiac anomalies are progressive and end in intrauterine death.

• Thus, the incidence quoted above may be only the tip of the iceberg.


• Fetal echocardiography, or the use of ultrasonic technologies to evaluate the fetal cardiovascular system, enables diagnosis of structural heart defects, and offers a way to observe complex physiological processes prior to birth


Indications for fetal echocardiography

A. Maternal indicationsCongenital heart diseaseCardiac teratogens

Isotretinoin ,lithium, ethanol, phenytoin etcMaternal metabolic disorders

Diabetes, phenylketonuria , gestational diabetesAutoimmune disorders

Sjogrens syndrome , SLEIntrauterine infections

Rubella


B. Fetal indications: Extra cardiac anamolies

Chromosomal and Anatomic(increased NT , GIT , RENAL , CNS ) Fetal cardiac arrythmias

Irregular rhythm , tachycardia(absence of amnionitis) , bradycardia Non immune hydrops Abnormal fetal situs Suspected fetal heart anomaly by screening ultrasound Chromosomal abnormalities Monochorionic twin gestation

Twin twin transfusion syndrome, conjoint twins


• Familial indications :History of CHD

Previous sibling , paternalMendalian syndromes

Williams syndrome , Digeorge syndromeConsanguinity


Indications for converting a routine scan into fetal echocardiography1. Chamber asymmetry2. Altered cardiac axis3. Altered position of the fetal heart4. Enlarged fetal heart5. Arrhythmia


TIMING OF FETAL ECHOCARDIOGRAPHY

• Fetal echocardiography is best performed between 18 and 22 weeks of gestation.

• After 30 weeks gestation, the shadowing effects of the fetal ribs, ratio of fetal body mass-to-amniotic fluid increases so acquisition of images more difficult. • Early maternal transabdominal or trans-vaginal scan at 11 to 14

weeks of gestation, in pt with Increased nuchal translucency.• In the first trimester (11–14 weeks), cardiac details may not be

elicited well, but the presence of a pulsatile ductus venosus or tricuspid regurgitation can be a very strong marker for cardiac and chromosomal anomalies.


Equipment &Technical aspects

• High frequency transducers probes for resolution and details

• Phased array transducers with fundamental frequencies between 4 and 12 MHz are generally used.

• Curvilinear probe with wider near-field of view.

• High frequency transducers with a narrower footprint


• Low frequency transducers and harmonic imaging ---3rd trimester and

• axial resolution of 1 mm or less this is particularly important given the

small size of critical fetal cardiac structures. • Frames rates of 80 to 100 Hz are frequently

needed to view important events occurring at heart rates in excess of 140 beats per minute


• Tissue Doppler imaging is useful in the assessment of fetal arrhythmia.

• decreased persistence, and increased compression. • The system should have the ability to zoom the

image without causing deterioration of image quality.

• A higher pulse repetition frequency (PRF) is required for colour Doppler in the fetus as compared to the settings used for routine obstetric colour Doppler.


Determining the laterality of fetal body and image orientation

• Most common used method for assesing laterality is proposed by cordes et all.

• It is effective when fetus is in transverse positionProcedure:• Obtaining sagittal view of fetal body. Align transducer in long

axis of fetus (spine)• Orient the transducer so that fetal head is on the right side of

observer on the screen• Rotate the transducer 90* clockwise to obtain a transverse

view of fetal body • Tranverse section thus aquired is caudocranial axis


Image orientation

• Craniocaudal• Caudocranial (standard view)• anatomical


orientation


Visceroatrial arrangement(situs)

• To assess morphological arrangement of atria• Appendages are most constant component of

atria• LA appendage is tubular and hook shaped

with narrow junction with venous portion of atrium

• Vestibular aspect of LA is smooth• Pectinate muscle is restricted to appendage


• RA appendage is triangular with broad junction with venous portion of the atrium

• Vestibular aspect of RA contain pectinate muscle

• There is close relationship between arrangement of atria and position of descending aorta and great veins at level of diaphagm


• Situs solitus descending aorta is left to midnline IVC to the right of midline stomach to the left portal sinus curves to the right predominant liver lobe to the right


Situs solitus vs inversus


Right vs left isomerism


Cardiac position and Axis orientation

• Cardiac position and axis can be assessed in four chamber view

• In this view by tracing sagital and coronal planes through centre of thorax four quadrants are identified

• Lv and most of RV and anterior part of LA lie in left anterior quadrant


Cardiac position


Axis orientation

• Axis of heart refer to its long axis• Axis orientation is expressed as the angle between a line

aalong the ventricular septum ,directed towards the cardiac apex and midline sagittal plane of thorax

• The normal cardiac axis is 45± 15°• . Altered axis is often associated with outflow tract

anomalies• Types levocardia Mesocardia dextrocardia


Axis of heart


Segmental analysis

• Segments– atria ventricles arterial trunks systemic and pulmonary veins• Connections-atrioventricular ventriculoarterial venoatrial


• Atria• LA appendage is tubular • Vestibular aspect of LA is smooth• RA appendage is triangular • Vestibular aspect of RA contain pectinate

muscle


Visceroatrial arrangement(situs)


Morphology of right ventricle


Morphological left ventricle


• Arterial trunk• Differentiated by branching pattern• Aorta – coronaries arise from sinuses run superiorly to form aortic arch and gives origin to

brachiocephalic vessels,CIA• Pulmonary artery runs anteroposteriorly and bifurcates

in right & left PA• Main PA connects to descending aorta via ductus

arteriosus


Arterial trunk


• Atrioventricular connection• Concordant: atrial chamber connected with

appropriate ventricle• Discordant: atrium is connected with

morphologically inappropriate ventricle• In isomerism morphologic RV is determined by

right and left hand topology(palm on septal surface and thumb in inlet and fingers in outlet of ventricle)


isomerism


• Ventriculoarterial connection• Concordant vs discordant• double outlet RV/LV


Echocardiographic projections

• Transverse views of fetal heart• Four chamber view• Five chamber view• Three vessel view• Arterial ductal transverse view• Aortic arch transverse view


Four chamber view

• Obtained from transverse plane of upper abdo men by tracing IVC to RA and then cranial angulation give 4 chamber view

• RV is more anterior with blunted apex• LV is posterior with ellipsoidal shape• LA most posterior and close to spine and

descending aorta


• Four chamber view:Symmetry of chambers Atrial Septum and PFO Ventricular Septum Atrioventricular Valves Ventricular functionRhythm abnormalities


4 chamber view


• Abnormalities of four-chamber anatomy may characterize certain forms of congenital heart disease

• In many cases, the primary structural abnormality of the heart may be apparent in the view of the central fibrous body. Such defects may include Complete atrioventricular septal (canal) defect, Hypoplastic left heart syndrome, Hypoplastic right heart syndrome, Ebstein malformation of the tricuspid valve, and Various forms of single ventricle


4chamber


• Dimensions of heart• CT circumference ratio normal– mean value of 0.45at 17 weeks and

0.50 at term• CT area ratio normal 0.25-0.35 throughout pregnancy


Ct ratio


• Measurement• Fractionalshortening= (EDD-ESD)/EDD Normal value 34%• End systolic and diastolic transverse diameters

of ventricles• Thickness of IVS,LV,RV• LA volume• Mitral & tricuspid annulus diameter


Lv diamension


• Normal Doppler flow profile of tricuspid and mitral valve :

• Similar • Diastolic pattern with 2 peaks E and A• 2 peaks merge with each other when heart

rate > 160-170 beats/min• No backflow into atria during systole


• E wave is smaller than A wave due to reduced fetal ventricular compliance so ventricular filling depend on regular atrial contraction( loss of sinus rhythm lead to fetal cardiac compromise)

• E wave increases throughout gestation with valu of 25cm/s at 16wks to 45cm/s at term for mitral valve and 30cm/s and 50cm/s for tricuspid valve

• A is relatively constant during gestation with 45cm/s for mitral and 50cm/s for tricuspid

• E/A ratio 0.5 at 16wks and 1 near term


• Colour flow mapping in normal fetus in 4 chamber view show equal and nonaliased flow through the atrioventricular valve in diastole .

• In systole no evidence of regurgitation across AV valves.


Ebstein anamoly with severe TR


• Colour flow mapping of pulmonary veins reflects variation in pressure in LA

• Systolic peak slightly higher than diastolic peak with small atrial reversal


Pulmonary veins


• Cardiac rhythm• By M-mode and pulse wave doppler• M-mode method: atrial and ventricular wall

moventment is recorded at same time in sinus rhythm atrial contraction preced

ventricular contractionBy PW doppler: by inflow and outflow pulse

doppler of LV


Cardiac rhythm


5 chamber view

• With cranial angulation from 4 chamber view give 5 chamber view

Structures seen are• Aortic valve and its root• Inflow ,trabecular and outflow of LV• LA and RA• Trabecular part of RV• Two pulmonary veins • SVC


5 chamber view


Useful to assess• Heart rhythm• LV outflow tract obstructions• Subaortic VSD


3 vessel view

• Obtained by sliding the scanning plane cephalad from four chamber view towards fetal upper mediastinum

• Significant lesions in ventricular outflow tracts show abnormal 3 vessel view

• Normally:• Pulmonary trunk is largest and anterior and left• SVC is smallest and posterior and right• Aorta is in between two• Show oblique axis of PA and short axis of aorta and

SVC


3 vessel view


• Ascending aorta is defined as small if its diameter is equal or smaller than SVC diameter

• Pulmonary artery is defined as small if its diameter is equal or smaller than aorta diameter


• 3 vessel view abnormalities :• Abnormal vessel size(HLHS)• Abnormal vessel alignment(subrterial VSD)• Abnormal arrangment(TGA)


Arch sidedness based on position of descending aorta in relation to spine


Arterial duct and aortic arch transverse view

• From transverse view of aortic arch slight caudal angulation to the left ,visualise arterial duct and aortic arch

Normal morphology• Aortic and ductal arches merges together into

descending aorta • Ductal arch larger than aortic isthmus and

both lie on left side


Arterial duct and aortic arch view


Aortic arch long axis view

• This view is obtained by parasagital plane with angulation from right of sternum to left shoulder

Normal morphology• Aortic arch in long axis(candy cane appearence)• Cross section of RPA • Isthmus is aortic segment between left

subclavian and aortic end of arterial duct


Aortic arch long axis view


colour flow mapping across aortic archFlow in aortic arch changes direction by 180* so

different segments of aorta are represented in opposite colours

Doppler spectrum is monophasic wave but with a diastolic forward flow due to diastolic recoil of aortic ach and low placental resistance


Arterial duct long axis view

• This view is obtained by parasagital plane with angulation from left of sternum to left shoulder

Normal morphology• The section show superiorly the main PA

which split into inferior branch (left PA) and superior branch(arterial duct)


Ductal view


• Arterial ductal flow assessment by pulse wave doppler

• Systolic anterograde flow < 50cm/s at 6 wks to 130-160cm/s at end of pregnancy

• Diastolic peak velocity 0 at early pregnancy to 30-40cm/s near term

• Diastolic wave is due to rebound of energy potentially stored by walls of main PA which produces further flow from PA to aorta


Bicaval view

• Obtained by orienting the scan plane along the true sagittal plane of fetal body immediately to right of midline

Normal morphology• Longitudinal section of SVC and IVC• RA and RAA• Cross section of RPA


• Caval flow • S wave –due to atrial suction produced by movement

of tricuspid valve plane in an base to apex direction during ventricular systole

• D wave—in early diastole ,correspond to reduction in atrial pressure due to AV valve opening

• A wave –retrograde wave in late diastole due to atrial contraction

• ratio between peak s and peak d wave is constant with value of 1.8 + 0.2 through out gestation


RV outflow view

• Slight left side rotation from sagittal plane (from right hypochondrium to left shoulder)

Normal morphology• Structures of right heart and crossection of

aortic root


LV long axis view

• Plane that runs from left hypochondrium to right shoulder

• Obtained by rotating transducer 90* from apical 4 chamber view and tilting towards right shoulder

• Useful in assessing inlet and outlet portions of LV• Subarterial and anterior muscular VSD can be

seen• Aortic override can be assessed in subortic vsd


Pitfalls

• Some lesions such as minor VSDs may be missed.• Progressive defects, such as a bicuspid aortic

valve, may not be diagnosed at 18–20 weeks of gestation.

• Outflow tract anomalies may be missed.• Maternal habitus and fetal lie may be limitations.• Visualization of details may not be possible

before 18 weeks.


Conclusion

• It may be difficult or time consuming to perform a dedicated fetal echocardiogram on all patients.

• Four-chamber view, the outflow tracts, and the three-vessel view would be sufficient to diagnose 80–85% of cardiac anomalies.


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fetal echocardiography

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