The Fetal Heart and Chest

The embryonic heart begins as two tubes. These two tubes ultimately fuse and fold to form into four chambers,

two atria and two ventricles.

The heart begins to contract at 36 to 37 days of gestation and is fully formed by 10 weeks. A heart rate using M-mode should be sonographically obtainable with endovaginal (EV) imaging when the crown rump length (CRL) measures

4-5mm

During a biophysical profile assessment in the third trimester, an average fetal heart rate is

150 beats per minute (bpm), with a range of 110 to 180 bpm considered normal after 1st trimester

what is biophysical profile

a method of fetal monitoring with sonography to produce a numeric scoring system that predicts fetal well-being

A normal fetal heart will fill about 1/3 of the fetal chest. If it is suspected that the heart is enlarged,

then a cardio/thoracic diameter ratio can be obtained.

4 chamber heart view will show

The apex of the heart will be angled to the left of the midline (same side as stomach as well), with the base closest to the spine.

the apex of the heart forms a __ angle with the spine

45 degree

The two atria are separated by the ____ septum, and the two ventricles are separated by the _______ septum.

atrium, ventricular

The ventricular septum should be uninterrupted and of equal thickness to the

left ventricular wall,

the atrial septum is open only at the

foramen ovale

Within the right ventricle can be seen the __________ ________ a normal structure that appears as an echogenic focus

moderator band

Between the right ventricle and the right atrium, one should visualize the

tricuspid valve,

between the left ventricle and the left atrium,

mitral valve should be noted

Normally, the tricuspid valve is positioned closer to the

cardiac apex than the mitral valve

The right ventricular outflow tract leads to the

pulmonary artery and branches

the left ventricular outflow tract leads to the

aorta.

One important anatomic finding is that the normal pulmonary artery should be positioned

anterior to the aorta and should be visualized crossing over it

The three-vessel view (3-VV) shows the

main pulmonary artery, ascending aorta, and superior vena cava

The 3VV is used to detect

abnormal vessel number, abnormal vessel caliber, abnormal course or alignment of the vessels, and abnormal flow

The three-vessel trachea view (3VT) is used to evaluate the major vessels in the fetal mediastinum as well. In the 3VT, a

“V” is formed by the merging of the transverse aortic arch and isthmus and the pulmonary trunk and ductus arteriosus

The 3VT is also used to assess the

number, size, and alignment of the main pulmonary artery, aorta, and superior vena cava.

Representative scan planes for fetal echocardiography

Basic assessment of the fetal outflow tracts

fetal circulation

what is ductus arteriosus

a fetal shunt that connects the pulmonary artery to the aortic arch

what is ductus venosus

a fetal shunt that connects the umbilical vein to the inferior vena cava

The normal umbilical cord contains two arteries and one vein. The umbilical vein brings oxygen-rich blood from the placenta to the

fetus

It travels superiorly and connects to the left portal vein. Half of the blood goes to the liver through the left portal vein, whereas the other half is shunted directly into the

Inferior vena cava (IVC) via a small branch of the umbilical vein called the ductus venosus.

The blood that was taken to the liver is used to oxygenate the liver and is then returned back to the

IVC via hepatic veins

The existing oxygen-rich blood in the IVC travels up to the heart and enters the right atrium. Blood can then travel across the

foramen ovale into the left atrium, or it can enter the right ventricle through the tricuspid valve.

The blood then leaves the right ventricle through the main pulmonary artery. The main pulmonary artery bifurcates into

right and left, thus allowing a small amount of blood to travel to the respective lung.

Blood from the right ventricle can also flow through the

ductus arteriosus and into the descending aorta

The blood returning from the lungs through the pulmonary veins enters into the

left atrium

Blood then travels from the left atrium into the left ventricle via the

mitral valve

From the left ventricle, it travels to the ascending aorta and into the aortic arch, where it exits into the

brachiocephalic artery, left common carotid artery, and left subclavian artery on its way to the thorax, upper extremities, and head.

The blood will return from the head and upper torso via the

superior vena cava to the right atrium

The blood that flows through the ductus arteriosus and into the descending aorta travels inferiorly to either exit the abdomen via the

umbilical arteries or travel to the abdomen and lower extremities to replenish those regions

Therefore, the umbilical arteries return the deoxygenated blood from the fetus back to the

placenta

What is Hypoplastic left heart syndrome

group of anomalies characterized sonographically as a small or absent left ventricle

Hypoplastic left heart syndrome is the leading cause of

cardiac death in the neonatal period, with 95% dying within the first month of life if surgery is not performed

To distinguish this anomaly from complete absence of the left side of the heart,

a small or normal left atrium must be visualized

When found in girls,

Turner syndrome should be suspected. There is also a connection with trisomy 18.

Sonographic Findings of Hypoplastic Left Heart Syndrome

Absent or small left ventricle

No communication between the left atrium and the left ventricle

Aortic atresia (possibly)

Aortic stenosis (possibly)

Coarctation of the aorta (possibly)

what is Hypoplastic right heart syndrome

sonographically identified as a small or an absent right ventricle

Hypoplastic heart syndrome most often results from

pulmonary stenosis or pulmonary atresia, but it may result from stenosis or atresia of the tricuspid valve.

Sonographic Findings of Hypoplastic Right Heart Syndrome

Absent or small right ventricle

Enlarged left ventricle

Fetal hydrops (secondary to cardiac failure)

Narrowing of the pulmonary valve

A ventricular septal defect (VSD) is an

abnormal opening in the septum between the two ventricles of the heart

The VSD is the

most common form of cardiac defect

Sonographic Findings of Ventricular Septal Defects

Absence of part of the ventricular septum

Color Doppler is helpful at detecting small defects

An atrial septal defect (ASD) is an

abnormal opening in the septum between the two atria of the heart. (types 1-5)

Sonographic Findings of Atrial Septal Defects

Absence of part of the atrial septum

Color Doppler is helpful at detecting small defects

The combination of both ASD and VSD is termed

atrioventricular septal defect (AVSD) or atrioventricular canal.

An AVSD results from the

abnormal development of the central portion of the heart.

The central portion of the heart is referred to as the

“endocardial cushion”; this is the reason why the AVSD may be referred to as an endocardial cushion defect.

AVSDs are commonly associated with

aneuploidy, trisomy 21, and trisomy 18.

Sonographic Findings of Atrioventricular Septal Defects

Absence of the atrial and ventricular septum

Color Doppler findings are helpful at showing mixture of flow patterns

what is Ebstein anomaly

Malformation or malpositioning of the tricuspid valve

The prognosis is poor, with

80% of infants dying in the perinatal period.

Sonographic Findings of Ebstein Anomaly

Malpositioned tricuspid valve

Right and left atrial shunting

Tricuspid regurgitation

Enlarged right atrium

Deviation of the atrial septum to the left

Fetal hydrops (secondary to cardiac failure)

Coarctation of the aorta is the

narrowing of the aortic arch

The most common location of coarctation of aorta is between the

left subclavian artery and the ductus arteriosus

Associated findings with coarctation of aorta consist of

right ventricle enlargement, pulmonary artery enlargement, and disproportion in the size of the ventricles in the four-chamber view

Sonographic Findings of Coarctation of the Aorta

Narrowing of the aortic arch

Right ventricular enlargement

Pulmonary artery enlargement

what is Tetralogy of Fallot

an overriding aortic root, subaortic VSD, pulmonary stenosis, and right ventricular hypertrophy (not always noted in utero but manifests after birth)

Sonographic Findings of Tetralogy of Fallot

Overriding aortic root

VSD

Pulmonary stenosis

Right ventricular hypertrophy

With transposition of the great vessels, the outflow tracts are

reversed

With transposition of the great vessels, the 4 chamber view will appear

normal

Sonographic Findings of Transposition of the Great Vessels

The pulmonary artery abnormally arises from the left ventricle, and the aorta abnormally arises from the right ventricle

The outflow tracts will be positioned parallel to each other rather than crisscrossing

VSD may be present

An echogenic intracardiac focus (EIF) is most often seen within the left ventricle of the heart. This is thought to represent the

calcification of the papillary muscle or chordae tendineae

An EIF may be seen in the normal fetus. However, there have been studies that have linked the incidence of an EIF with

trisomy 21, particularly if there is more than one EIF detected.

Sonographic Findings of an Echogenic Intracardiac Focus

Echogenic structure most commonly located within the left ventricle

what is a Rhabdomyoma

tumors, located within the myocardium of the heart

Rhabdomyomas are associated with

tuberous sclerosis, eventual cardiac failure, and subsequent development of fetal hydrops

The most common fetal cardiac tumor is the

rhabdomyoma

Sonographic Findings of a Rhabdomyoma

Echogenic tumor(s) within the myocardium of the heart

what is Pericardial effusion

fluid located around the heart

Pericardial effusion can be isolated or associated with

fetal hydrops

It is important to note that the normal hypoechoic appearance of the myocardium can mimic the sonographic appearance of small

pericardial effusions.

Sonographic Findings of Pericardial Effusion

Anechoic fluid surrounding the heart

what is ectopic cordis

heart is located either partially or completely outside the chest

what is Pentalogy of Cantrell

group of anomalies that combine ectopic cordis and an existing omphalocele, prognosis is poor

Sonographic Findings of Ectopic Cordis

Heart located either partially or completely outside the chest

what is Pulmonary hypoplasia

underdevelopment of the lungs, is caused by a decreased number of lung cells, airways, and alveoli.

Pulmonary hypoplasia is often associated with

major structural and chromosomal abnormalities

The most common lesion that occupies the chest, resulting in pulmonary hypoplasia, is the

diaphragmatic hernia

Amniotic fluid plays an important role in the development of the fetal lungs; therefore, the fetus, surrounded by little or no amniotic fluid, is at

increased risk of pulmonary hypoplasia

Consequently, pulmonary hypoplasia is a common finding with

oligohydramnios

pulmonary hypoplasia is also associated with

bilateral renal agenesis and the abnormal facial features in the condition known as Potter syndrome.

what is pleural effusion

aka hydrothorax; Fluid surrounding the lungs

Pleural effusions that occur in utero may spontaneously resolve or may be found in the presence of

fetal hydrops, other chest abnormalities, and Turner syndrome

Fetal pleural effusions can be treated with an ultrasound-guided

thoracentesis

Sonographic Findings of a Pleural Effusion

Anechoic fluid surrounding the fetal lung(s)—“bat-wing” sign

Other signs of hydrops may be present

what is Cystic adenomatoid malformation (CAM),

also referred to as congenital cystic adenomatoid malformation (CCAM), is actually a mass consisting of abnormal bronchial and lung tissue.

Sonographic Appearance of Cystic Adenomatoid Malformations

Lung mass with varying degrees of cystic and solid components

Completely echogenic mass within the lungs

Pleural effusion may be present

what is Pulmonary sequestration

or bronchopulmonary sequestration, is a separate mass of nonfunctioning lung tissue with its own blood supply. The fetal form of this disease is specifically referred to as extrapulmonary sequestration

Sonographic Findings of Pulmonary Sequestration

Echogenic, triangular-shaped mass within the fetal chest

Pleural effusion may be present

The most common reason for fetal cardiac malposition is the existence of a

diaphragmatic hernia

what is a diaphragmatic hernia

abnormal opening in the fetal diaphragm that allows the herniation of abdominal contents into the chest cavity.

The most common location of a diaphragmatic hernia is on the

left side; may also be referred to as a Bochdalek hernia

The foramen of Bochdalek is located in the

left posterolateral portion of the diaphragm