1
Q
Which congenital cardiac defects result in cyanosis?
A
- Transposition of great vessels
- Tetralogy of Fallot
- Truncus arteriosus defects
- Critical pulmonary stenosis
- Tricuspid valve atresia
2
Q
Which congenital cardiac defects does not result in cyanosis?
A
- Atrial septal defect
- Ventricular septal defect
- Atrioventricular septal defect
- Patent ductus arteriosus
3
Q
From which embryonic tissue type do the initial pair of heart tubes develop?
A
- Cardiogenic mesoderm
4
Q
What happens to the initial pair of heart tubes during embryonic folding?
A
- Angioblastic cords canalise to form two heart tubes that fuse and subsequently expand
- Folding occurs due to growth of the heart tube and fixed positions of the aortic arches and venous input
5
Q
In which direction should the developing heart tube fold?
A
- Atrium moves cranially, dorsally and to the left
- Bulbus cordis moves caudally ventrally and to the right
- Ventricle normally sits anterioly and atria posteriolrly
- So fold occurs towards the right
6
Q
Which condition occurs if the heart tube folds in the opposite direction to normal?
A
- Dextrocardia
- Ventricle pointing toward right hand side
- Outflow tracts projecting more toward left hand side
7
Q
What are the names of the five regions of the growing heart tube?
A
- (From venous input)
- Sinus Venosus
- Atria
- Ventricle
- Bulbous Cordis
- Truncus Arteriosus
- (to Aortic sac)
8
Q
Which region of the heart does each of the growing heart tube regions become (or contribute towards)?
A
- Sinus Venosum - Smooth walled part of RA
- Atria - Rough walled parts of L&R Atria (eg auricle)
- Ventricle - Ventricles
- Bulbous Cordis - Part of outflow tract of both left and right ventricles (may form parts of right ventricle)
- Truncus Arteriosus - Ascending aorta and pulmonary trunk
9
Q
What is the dorsal mesocardium and what should happen to it?
A
- Dorsal mesocardium initially suspends the heart tube but will eventually disappear to allow heart tube to grow and fold
10
Q
Which structures do the parietal and visceral pericardium cover and where do they meet?
A
- Reflect off the great vessels where they meet the heart. Cover the whole heart
11
Q
Is an ASD (Atrial Septal Defect) a congenital cyanotic cardiac defect?
A
NOT Usually
12
Q
What does an Atrial Septal Defect (ASD) lead to?
A
- Left-to-right shunt after birth
- However, some ASDs are asymptomatic, Some close during growth
- Usually NOT a congenital cyanotic cardiac defect
13
Q
Describe the formation of the pulmonary veins? What happens to the initial part of the pulmonary venous system?
A
- Pulmonary veins grow out of the left atrial wall and branch (Primordial pulmonary vein)
- Proximal parts get incorporated into and form the smooth part of the atrial wall - Large proportion.
14
Q
Describe the process of atrial Septation
A
- Atrial septum forms during weeks 4 and 5
- Endocardial Cushion (EC) tissue begins to grow within the atrioventricular canal.
- Septum grows and divides Right and Left Atria and ventricles as well as aorta and pulmonary trunk
15
Q
What is the endocardial cushion? Which passageways sit either side of the EC?
A
- Tissue which grows within the atrioventricular canal and serves as the point at which division of the left and right occurs through
- Tricuspid and Bicuspid valves sit either side of the EC
16
Q
Which part of the atrial septum is relatively rigid and which part is relatively floppy?
A
- Septum Secundum - Relatively Rigid
- Septum Primum - Relatively floppy
17
Q
For what functional purpose is the atrial septum formed from two separate tissue with different properties?
A
- To allow for R->L shunting of blood from Right atrium to Left atrium in-utero where the lungs have not developed yet
18
Q
In which direction does blood shunt between the atria (and ventricle) in-utero? Why does blood shunt in this direction in utero?
A
- Right to Left
- To bypass lungs as they are not functional until birth
- Lungs fluid filled
- High pulmonary vascular resistance
- More blood entering right atrium vs left
- Blood shunted through foramen ovale
- Due to right side pressure exceeding left side pressure
19
Q
What happens after birth that normally leads to an instant closure of the foramen ovale?
A
- Lungs drained, air filled and functional (first breaths)
- Reduced pulmonary vascular resistance
- Greater pulmonary blood flow
- More blood entering left atrium
- Valve of foramen ovale closes as pressure in left side exceeds pressure in right side
20
Q
What is a probe-patent foramen ovale? Is this an issue in an otherwise healthy adult?
A
- Sometimes the tissues of the atrial septa do not fuse over time after birth. Means blood could still be passed through the shunting route from RA->LA.
- Normally non-problematic in otherwise healthy adults
- Can get leakage through during Valsava manouvre as briefly right-sided atrial pressure may exceed left
21
Q
When might a probe-patent foramen ovale be an issue and with what consequence?
A
- If the patient has a venous embolus
- May pass through right atrium to left side of the heart
- Potentially blocking a coronary artery
22
Q
What is an atrial septal defect? (ASD)? In which direction will blood shunt through an ASD after birth and will this result in cyanosis?
A
- Results in blood shunting L–>R Atria as pressure higher in LA after birth
- Does not result in cyanosis usually
23
Q
In which part of the Ventricular septum do defects occur most often? Why?
A
- Membranous tissue of septum
- Congenital heart failure?
- 80% of Ventricular Septal Defects
- Due to Membranous region being more complex to form. Relying on multiple pieces of tissue growing and joining as heart itself is growing and moving
24
Q
How does Aorticopulmonary septum tissue rotate/move during development
A
- Rotates through 180degrees as it passes cranially away from the heart
- Results in pulmonary trunk and aorta changing positions relative to each other
25
What is the result of Aorticopulmonary septum formation
- Rotates through 180 degrees and passes cranially away from the heart as Truncal ridges and Bulbar ridges meet
- Thus, most Inferior level PT Anterior to Aorta
- Ascends to sit left side of Aorta
- Most Superior level PT Posterior to Aorta
26
Describe Transposition of great vessels
- Great vessels transposed (Aorta connected to RV and PT connected to LV)
- Creates two isolated circulations connected only by the ductus arteriosus
- Cause debated:
- Maldevelopment of conus arteriosus
- Maldevelopment of aorticopulmonary septum
27
Why would an ASD, VSD, or patent ductus arteriosus be beneficial in a patient with transposition of the great vessels after birth?
- These defects can result in an alternative pathway for blood flow to partially correct for the transposed blood flow????
28
Describe Common (persistent) Truncus Arteriosus
- Failure of bulbar/truncal ridge formation results in a common arterial outflow tract sitting over (overriding) a VSD (ventricular septal defect)
- Common arterial outflow tract = Common truncus arteriosus
- Will receive blood from both L+R Ventricle
- Mixing of oxygenated and deoxygenated blood will result in newborn having cyanosis
29
What is Tetralogy of Fallot
0. Represents a collection of four cardiac issues
1. Pulmonary stenosis
2. RV Hypertrophy
3. Over-riding aorta
4. VSD
30
Describe the process of ventricular septation
- Muscular tissue grows from floor of ventricles toward Endocardial Cushion tissue + Aorticopulmonary septum grows down to meet
- Ventricular septum forms from muscular (majority) and membranous parts.
31
From which tissue types is the ventricular septum formed?
- Muscular tissue
- Endocardial Cushion tissue
- Aorticopulmonary tissue
32
Describe the formation of the septum in the arterial outflow tract (truncus arteriosus and Bulbus cordis) of the heart and how it contributes to the formation of the ventricular septum
- 2 Bulbar ridges grow from Bulbus cordis region of arterial outflow tract
- 2 Truncal ridges grow from Truncus arteriosus region of arterial outflow tract
- These grow toward to meet each other = Aorticopulmonary septum formation
- Rotates through 180degrees as it passes cranially away from the heart
- Extends inferiorly to meet endocardial cushion and muscular tissue to complete ventricular septm
33
What does Aortic Coarctation mean
Narrowing of the aorta
34
What can lead to aortic coarctation?
- Defects in aortic arch formation
- Defects in Remodelling process during aortic arch formation
- During closure of ductus arteriosus following birth
35
How is the position of Aortic Coarctation classifed?
- Relative to its positional relationship to the ductus arteriosus
- Preductal, juxtaductal or postductal
36
What are the aortic arch vessels and where are they initially located?
- The vessels which will develop into many of the great vessels in the adult
- Initially located within Each embryological pharyngeal arch - One aortic arch vessel on both left and right sides
- 6 pharyngeal arches but Arch 5 disappears during development
37
How many aortic arches are present initially, how many disappear and how many develop?
- 6 x2
- Arch 5 disappears
- 5 Develop x2
38
Which major arteries are formed (or contributed to) by aortic arch vessels 3, 4 and 6?
- Pulmonary trunk, Ductus arteriosus, Aortic arch, Brachiocephalic trunk,
39
Why does the left recurrent laryngeal nerve sit under the aortic arch and the right recurrent laryngeal nerve sit under the right subclavian artery?
- L RLN - Sits under Aortic arch as it is associated with Pharyngeal arch 6 and thus gets trapped under the proximal portion of Left aortic arch 6 which forms the ductus arteriosus - Staying trapped in this region after birth
- R RLN - Sits under left aortic arch 6 distal region which degenerates during development, R RLN ascends to next vessel it gets trapped under which is right aortic arch 4 which forms the proximal portion of the right subclavian artery
40
Which clinical examination findings can aortic coarctation cause? By which routes can arterial blood bypass the coarctation (think about blood supply to the thoracic and abdominal walls)
???
Block 2
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