How large is the isthmus of AO in relation to ascending & descending AO?
1/3 of the diameter
What happens to the AO isthmus of a fetus once it’s born and begins to grow? Why?
It enlarges after birth once the ductus arterious closes
Where is the isthmus of the fetal AO located?
Just distal to the subclavian artery
3 branches of AO arch starting closest to spine & vessel inferior to arch and branches
1. LT subclavian artery
2. LT CCA
3. Innominate artery
4. RT pulmonary artery
Most anterior structure of normal fetal heart?
RT Ventricle
Moderator Band:
Where is it located?
What is it near?
What does it do to the lumen
-RT Ventricle
-Apex of the heart
-Gives RT Ventricle shorter lumen & more trabecular appears
Which chamber of the heart is most posterior?
LT Atrium
Which chamber of the heart accepts the pulmonary veins?
LT Atrium
Which chamber of the heart accepts the foremen ovals flap
LT Atrium
3 characteristics of the LT Ventricle
1. Mitral Vslve
2. Smooth walls
3. 2 papillary muscles
Which chamber has finger-like thin appendages?
LT Atrium
4 normal characteristics of a normal RT Ventricle?
1. Has moderator band
2. Very trabeculated
3. Tricuspid valve
4. Triangular
Interventricular Septum:
1. What should be measured, when, & in what view?
2. What should the thickness remain & how long?
1. Ventricular wall thickness, end diastole, & 4ch
2. Less than 5mm throughout gestation
What are the fetal heart shunts?
1. Ductus Venosus
2. Ductus arteriosus
3. Foramen ovale
What does the ductus venosus do?
Allows oxygenated blood from the umbilical vein to bypass the liver & enter directly into the IVC
What does the ductus arteriosus do?
Allows blood from pulmonary trunk to bypass lungs & shunt into AO arch & descending AO
What does the foramen ovale do?
Allows oxygenated blood to flow from RT Atrium to LT Atrium
How many cusps are in a normal aortic valve
3
What is the location of the mitral valve in relation to the tricuspid valve?
MV is posterior to TV & TV Is more apical (doesn’t feel right, but this means MV is inferior to TV)
How many leaflets does the mitral valve have & what is it continuous with?
2 leaflets
Is seen in continuity with the posterior wall of the aorta
Where is the semilunar valves in relationship to each other?
Aortic valve is to the RT & posterior to the pulmonic valve
Which structures drain into the RT Atrium in a normal fetal heart?
SVC, IVC, coronary sinus
What heart structure is normally seen in the LT atrioventricular groove?
Coronary sinus
Best heart view for evaluating the fetal coronary sinus?
Apical 4 chamber
Which vessel supplies blood flow to the LT Ventricle & LT Atrium?
LT Coronary artery
Which artery originates from the LT side of the ascending AO at the level of the AO root & has 2 major branches that supply blood flow to the heart muscle?
Left coronary artery
What structures form the ductal arch?
Pulmonary artery
Ascending AO
Ductus arteriosus
What vessels in the fetal circulation takes the majority of right ventricular blood flow from the pulmonary artery, allowing most of the blood to bypass fetal lungs?
Ductus arteriosus
During a segmental exam for fetal position & situs, what is the hypoechoic organ positioned in the left upper ABD below fetal diaphragm in normal fetus?
Stomach
When determining fetal situs, you should evaluate the spleen as well as the liver. Where is the spleen located in a normal fetus?
LT upper ABD below diaphragm
To rule out isomerism, what must you note when scanning through the fetal ABD during an echocardiography exam?
Spleen
Liver
AO
IVC
What is isomerism aka?
Heterotaxy
What is isomerism?
abnormal assembly of the thoracic and abdominal organs from the normal arrangement known as "situs solitus”
When the trachea is displaced, what should the differential diagnosis include? What sonographic view should be obtained to make this diagnosis?
Right sided Aortic arch
3VV
The normal fetal heart occupies what percentage of the thoracic cavity?
Less than 30%
What is considered cardiomegaly?
When the fetal heart occupies more than 33% of the thoracic cavity
What are the sonographic features of the fetal esophagus? What is the size?
1. The esophagus appears as a tubular echogenic structure with a pattern of two echogenic lines
2. The size of the esophagus varies with fetal swallowing
What is the initial step in any fetal echocardiographic exam?
Establish fetal position
After identifying the fetal position and right and left orientation what is the next step in the sequential segmental analysis?
Identify the location and orientation of the heart Apex along with the visceral/abdominal situs and stomach position
Which term describes a fetal heart that is situated in the fetal right chest with the Apex pointing to the left?
Dextroposition.
What is dextroposition?
Heart is in the RT chest & Apex points left
What is levoposition?
The heart is in the left thorax
What are 5° that are normal for lexoposition and what degree would be considered abnormal?
1. Normal: 45°, 25°, 65°, 35°
2. Abnormal: 20°
What is dextrocardia?
The fetal heart points towards the right side of the chest
What is mesocardio?
Heart is midline
What is dextroposition?
The contents of the left side of the chest shove the heart to the right and heart moves toward the sparsely occupied space on the right.
What is Levocardia?
Reversal of all abdominal & thoracic organs (situs inversus) except the heart, which is still in its usual location on the left.
What is Levorotation?
Counter clockwise rotation of the heart
What term describes the Apex of the heart pointing to the fetal left chest with the apex at 45°?
Levocardia
What is the normal heart position in a fetal thorax called?
Levocardia
What is the most leftward structure in the fetal heart?
Main pulmonary artery
When you’re scanning through the normal Fetal heart in a sub costal 4 chamber view, what structure or structures should you see entering the left atrium?
Pulmonary Veins
Pulmonary artery:
1.how does it bifurcate?
2.where are the pulmonic valves?
3.what does the pulmonary artery cross over & where?
4. what is the pulmonary artery larger than?
1. Bifurcates into the rt & lt pulmonary branches
2. Anterior to the aortic valve
3. It crosses over the aorta anteriorly
4. The pulmonary artery is larger than the aorta
How many pulmonary veins drain into the left atrium?
4
Where does the normal left pulmonary artery course?
Superior to the left bronchus
When evaluating the fetal abdomen in a trv plane at level of stom, tech sees what vessels to RT of AO, just anterior to the fetal spine?
IVC
Which vessel allows blood to bypass the liver in the fetal circulation?
Ductus venosus
Multiple echoes within the right atrium can represent what?
Both the eustachian valve and Chiari Network.
What is the eustachian valve in the right atrium the valve of?
The IVC
What is the Chiari network?
Network of fibers from the eustachian valve & connecting to different parts of the right atrium
What functions as the pacemaker of the fetal heart?
Sinoatrial node
Where does rhythmic beating and heart contractions originate in the fetal heart
Sinoatrial Node
Where is the sinoatrial node located
RT Atrium
What 4 other names is the sinoatrial also known as?
What does the E/A wave ratio of the mitral valve do as pregnancy advances?
Increases as pregnancy advances
What is the normal range for the E/A ratio?
0.5-1.0
What is the E wave measurement at 16wks gestation and what is it at term? What does the A wave do throughout pregnancy?
-It increases from 25 cm/sec at 16wks to 45 cm/sec at term
-it remains constant throughout pregnancy
What is a normal Fetal heart rate in the second trimester?
100-180 bpm
T/F: The fetal heart rate remains constant throughout gestation
False
What forms the definitive AO?
4th LT AO arch & common dorsal AO
What is the normal range of a 15 week fetal heart rate?
100-180 bpm
Where does fetal gas exchange take place?
In the placenta
What 3 things does the patent ductus arteriosus do in utero?
1. Shunts blood right to left
2. Shunt blood from pulmonary artery to aorta to bypass lungs
3. Has a normal pulsatility index of 1.9-3.0
What drug can constrict the normal patent ductus arteriosus in utero?
Indomethacin
Which vessel in fetal circulation regulates the amount of blood flow to the heart and what does this prevent?
1. Ductus venosus
2. Prevents overload of volume to the fetal heart
The majority of blood flow entering the right atrium flows to the left atrium via what?
Foramen Ovale
What enzyme is released by the neonatal lungs shortly after birth? And what does this stimulate?
Bradykinin
Closure of the ductus arteriosus
What vessel connects the ductus venosus to the heart?
IVC
What does the ductus venosus come off of and connect to?
Umbilical vein & connects to IVC
What does cardiac output do with gestational age?
Cardiac output increases with gestational age
Which chamber of the heart ejects the majority of the cardiac output? And approximately how much does this chamber eject? And where is this output through?
The right ventricle
2/3 of total ventricular cardiac output
Most is thru the ductus arteriosus
What is the percentage of oxygen saturation in the umbilical vein?
80-90%
How does the blood flow out of the fetus? Where does it go? And how much of that blood is oxygen saturated?
Through the umbilical arteries
To the placenta
Oxygen saturation is 58%
Which chamber does blood from the lungs enter and via what?
It enters the left atrium via the pulmonary veins
During embryologic development what does the fourth left aortic arch and the common dorsal aorta become?
Definitive aorta
What will abnormal looping of the heart tube to the left result in?
It results in ventricular inversion aka Corrected transposition of the great arteries
During what window in fetal heart development does the fetal heart begin to beat?
21-28 days
In the sequence of fetal heart development what is the last to form embryologically? And when is this complete
Semilunar valves
9 wks gestation
What comprises the semilunar valves?
The aortic valve in the pulmonary valve
At which gestational week is a fully septated fetal heart achieved?
Week 8
What do the 4 pulmonary veins enter into? And what 3 things form these 4 pulmonary veins?
Left atrium
When the common, LT, RT pulmonary veins are absorbed
What are Endo cardio cushions involved in the development of?
1. Semilunar valves
2. Atrioventricular valve
3. septum
What 4 syndromes are thought to be a result of a midline developmental field defect?
1. Polysplenia syndrome
2. Asplenia syndrome
3. Ivemark syndrome
4. Right atrial isomerism
When does organogenesis occur?
Between 4-8 weeks
What is the result of the primitive heart tube loops to the right?
A normal great artery relationship
At approximately what gestational age does the partitioning of the embryonic fetal heart into the chambers of the atrial and ventricles begin?
Day 28
What 3 things is coarctation of the aorta thought to be a result of?
-Aberrant ducts tissue
-Decreased blood flow through the aortic isthmus
-Failure of the 4th & 6th aortic arch to connect with the descending aorta
According to the AIUM when is a fetal echocardiogram most commonly performed?
18-22wks
A transvaginal fetal echocardiography may be performed as early as when?
11-16weeks
Ductal arch: communication btwn what? What is it formed by? What are you imaging?
1. AO & pulmonary trunk
2. AO, pulmonary artery, & DA
3. Ductus arteriosus
Cardiac biometry: what valves should be measured & when in the heart cycle?
-Aortic & pulmonary annulus in systole
-Tricuspid & mitral valve annulus in diastole
What makes a 5 chamber view?
In a 4ch view move XDR slightly upward to visualize the aortic valve arising from LVOT in the center of the 4 chambers
