Cardiovascular embryology Flashcards
Malformations of the heart most commonly occur between what timeframe?
Weeks 3-8
Name the precursor structures in the process of cardiac development
When does the embryological heart start to pump blood?
What structure receives venous drainage?
What structure pumps blood out?
Blood flow: 24 days (unidirectional
Venous drainage received: caudal pole
Blood pumped out: cranial pole
What are the primitive chambers of the heart present at 24 days?
They are the precursors for what structures?
-
Sinus Venosus: receives blood
- smooth walled portion of right atrium
- coronary sinus
-
Primordial Atrium:
- pectinate muscles of right & left atria
-
Primordial Ventricle & Bulbus Cordis
- right & left ventricle
-
Truncus ateriosus
- will divide into aorta & pulmonary trunk
How does the heart change shape as it continues to grow longitudinaly?
Since the heart is anchored at the cranial and caudal ends, it begins to the right bend as it continues to grow longitudinaly, pushing the primitive ventricle to the left
Forms a C-shaped structure, but then the two ends of the C start to twist producing an S-shaped structure
Producing a 4 chambered heart
Once the 4-chambered heart has developed, what is the next step in development?
Remodeling of the chambers
Formation of septa and valves
What happens if the heart bends to the left instead of the right?
What can cause this to happen?
Dextrocardia
Apex ends up in the right chest (midclavicular)
-
Causes
- primary ciliary dyskinesia (dyein defect)
- dyein = microtubular motor
- sample from trachea (look at cilia)
- each doublet should have 2 crab claws
- may have infertility & COPD
- Situs inversus
- when all the organs are flipped around
- embryonic arrest of the movement of the heart
- primary ciliary dyskinesia (dyein defect)
Future partitioning of the heart is dependent on what 3 major septa?
Once they are formed, they produce what chambers?
- Interatrial septum
- separation of atria
- Interventricular septum
- separation of ventricles
- Aorticopulmonary septum
- separation of outflow tract
- separation of aorta/pulmonary trunk
What defects are caused by failed heart partitioning?
-
Interatrial septum:
- atrial septum defect
-
Interventricular septum
- ventricular septum defect (most common)
-
Aorticopulmonary (spiral) septum (most severe)
- failure to separate ventricular outflow
- transposition malformation of aorta/pulmonary trunk
Describe the steps involved in partitioning of the atria.
- Partitioning of the atria
-
Septum primum (crescent-shaped membrane on posterior, superior, inferior parts of primordial atrium)
- divides left & right atria
- Leaves opening (foramen primum)
- between the atria
- septum fuses to the cushions
- foramen primum closes
-
Septum primum (crescent-shaped membrane on posterior, superior, inferior parts of primordial atrium)
Why is it important for the left and right atrium to communicate during development?
all of the oxygen is coming in through the right atrium through the umbilical vein, but systemic circulation is out of the left ventricle, so the blood needs to cross right atrium into the left atrium to get to the rest of the embryo
When the septum primum closes, how does the embryo continue to move blood from the right atrium to the left atrium?
What is the final foramen used to transfer blood from the right atria to the left & what steps are involved in its development?
- Apoptosis of cells in septum primum
- channels are formed, eventually producing foramen secundum
-
Septum secundum is formed on the anterior of the atria & to the right of the septum primum
- thick muscular ridge
- crescent shaped
- forms the interatrial septum
- As it grows, it leaves an opening
- Foramen ovale
- covered on the left by the remaining septum primum, so end up with sort of a complete wall
- Remnant of septum primum becomes the valve of the foramen ovale, ensuring unidirectional flow of blood from the higher pressure atrium
When does the foramen ovale close?
When a baby takes its first breath, blood will fill the left atrium from the pulmonary veins, increasing the pressure in the left atria.
This inreased pressure will push the valve of the foramen ovale against the interatrial wall & eventual fuse
How can you differentiate between a left-to-right shunt and a right-to-left shunt in a newborn baby?
Which congenital heart defects can cause these problems?
-
Left-to-right:
- no cyanosis at birth
-
Defects:
- Atrial septal defect
- Ventricular septal defect
- Patent ductus arteiosus
-
Right-to-left:
- early cyanosis (blue baby syndrome )
- deoxygenated blood goes into systemic blood
-
Defects
- __Persistent truncus arteriosus
- Transposition of great vessels
- Tricuspid atresia
- Tetralogy of Fallot
- Hypoplastic left heart syndrome
- early cyanosis (blue baby syndrome )
What is an Atrial Septal Defect?
How is it diagnosed?
Major complications?
What are the most common types?
-
Flow between the atria
- (pressure higher on left side)
- Split S2 sound
- delayed closure of the pulmonary valve
- Diagnostic: ultrasound bubble study
- saline w/ bubbles & inject into anticubital vein
- expect to see them in right atrium
- Complications
-
paradoxical embolism
- if a clot is produced in a lower limb, makes its way to the right atria and then crosses over to the left atria
- it can now enter circulation & theorhetically make its way to the brain & cause a stroke
-
paradoxical embolism
- Most common types
-
Ostium secundum defect (90%)
- excessive resorption of septum primum or inadequate development of septum secundum
- excessive resorption of septum primum
- inadequate development of septum secundum
-
Ostium secundum defect (90%)
- other types
- ostium primum defect (Down syndrome)
Partitioning of the ventricles occur at what timepoint in development?
Describe this process
Where are defects most commonly seen in this process?
- 4 weeks
-
Groove starts forming in the middle of the primordial ventricle
-
bluges in and forms a big muscular septa
- precursor for muscular intraventricular septa
- does not reach atrioventricular wall – it stops and leaves an interventricular foramen
- membranous interventricular septum will develop over the the i_nterventricular foramen_, separating the ventricles (location of most congenital defects)
-
bluges in and forms a big muscular septa
What is a ventricular septal defect?
How common is it?
Diagnostic features?
It can cause what types of complications?
It is associated with what risk factor?
- Membranous interventricular septum does not fully form
- Most common congenital cardiac malformation
- Features
- left-to-right shunt
- no early cyanosis
-
pansystlic heart murmur
- created by shunting of blood (small ones make more noise)
- Complications
-
pulmonary hypertension
- pressure is building up on right side of the heart, causing right ventricular hypertrophy, eventual equalizing the pressures between the right & left ventricles
- blood will start crossing back from the right to the left
- Eisenmenger Syndrome
- late cyanosis
-
pulmonary hypertension
- Associated Risk factor
- Fetal alcohol syndrome
Describe the process of partitioning the trucus arteriosus
What is the name of the septum produced?
Aorticopulmonary septum (Spiral septum)
Spiral course (180 degrees)
Fuses with interventricular septum
What can happen if the spiral septum goes straigh down and does not twist 180 degrees?
Features?
Treatment?
Association with risk factors?
-
Transposition of the great vessels
- Aorta –> right ventricle
- Pulmonary Artery –> left ventricle
- This creates two closed circuits
- From right ventricle, to systemic circulation, and back to the right atrium
- From left ventricle, to lungs, and back to left ventricle
- May still have a connection through the persistent ductus arteriosis – if this is not present, the baby will die
- Early cyanosis
- Treatment
- Administer prostaglandins (PGE)
- to keep open the persistent ductus arteriosus (PDA)
- Surgery
- Administer prostaglandins (PGE)
- Association
- Maternal diabates
What is the defect where the truncal and bulbar ridges fail to fuse?
Features?
It is often accompanied by what other features?
-
Persistent truncus arteriosus
- aorticopulmonary (spiral) septum is not formed
- single outflow from both ventricles
- mixing of blood
- Early cyanosis
- Accompanied by
- ASD
- VSD
What is Tricuspid atresia?
Features of this defect?
It is often accompanied by what other defects?
- Tricuspid valve is not formed (no connection between right atrium and right ventricle)
- Features
- hypoplastic right bentricle
- early cyanosis
- Accompanied by
- ASD
- VSD
What is Hypoplastic left heart syndrome?
Treatmet?
- Virtually no left ventricle
- All the blood that comes in eventually ends up in right ventricle & sent out into massive pulmonary artery that has big ductus arteriosus
- so pulmonary artery supplies blood to both the systemic circulation and the lungs
- Treatment
- Surgery or Heart Transplant
What causes Patent Ductus Arteriosus (PDA)?
-
Ductus Arteriosus does not close at birth
- at birth blood will start flowing from aorta back to pulmonary trunk
- Features
- machine-like murmus
- Can lead to:
- pulmonary hypertension
-
Eisenmenger syndrome
- pressure in right heart big enough that it can reverse flow of blood
-
lower extremity cyanosis (differential cyanosis)
- b/c ductus arteriosis connects to the aorta after the 3 first main trunks
- Association
- congenital rubella
- Treatment
- NSAIDS (indomethacin): decrease prostaglandin (PGE)
What are the two types of Coarctation of the aorta & features of each?
- Infant
- associated with PDA
- Pre-ductal
- LE cyanosis
- Turner syndrome
- Adult
- post-ductal
- rib notching
- delayed LE pulses
- bicuspid aortic valve
