Module 1: Basic Embryology and Septal Defects Flashcards
when is the heart formed in the fetus
3-7 weeks gestation
which organ is the first develop in the fetus
heart
at week 3 what structure begins to appear
- the cardiogenic area
where is the fetal heart tup located
- within the pericardium
what is the direction of the blood flow in the endocardial tube
- unidirectional
what must the heart tube do to form the heart
- heart tube must fuse and twist
where is the trunks arteriosis located
- remains near the superior part of the heart
what structures are formed from the trunks arteriosis
- semilunar valves
- aortic root and pulmonary root
what does the looping of the heart form
- forms the 2 atria and 2 ventricle
what is the normal direction of looping
- right wards
what is the abnormal direction of looping and what does it result in
- leftwards
- left transposition of the great arteries
what are the three stages of atrial septal formation
stage one - septum premum stage two - foramen secundum stage three - secundum septum stage four - foramen ovale valve stage five - at birth
stage one of atrial septal formation: septum premum - what does the septum premum separate
- divides atrium into right and left halves
stage one of atrial septal formation: septum premum - where is the origin of the septum and where does it travel
- extends downward from roof of common atrium
- towards the endocardial cushions
stage one of atrial septal formation: septum premum - what is the foramen premum
- between the lower margin of the septum primum and the endocardial cushion
stage two of atrial septum formation: foramen secundum - how is the foramen secundum formed
- septum primum grows inferiorly toward the endocardial cushions closing the foramen primum
- a perforation appears int eh upper portion of the septum primum becoming the foramen secundum
stage three of atrial septum formation: secundum septum: where is the origin of the secundum septum and what does it form
- grows inferiorly to eh right of the septum primum
- this partially overlaps the foramen secundum
- forms the foramen ovale
what pressure keeps the flap of the foramen ovale open
- increased right atrial pressure in the fetus
stage four of atrial septum formation: foramen ovale valve - how is the valve formed
- upper septum primum disappears
- lower part of septum primum becomes the valve for the foramen ovale
- the septum secundum starts growing superiorly from AV cushions
stage five of atrial septum formation: at birth - how is the foramen ovale shut
- increased systemic vascular resistance + decreased RA pressure
- the increase in pressure pushes the valve against the septum secundum closing the hole
- eventually they fuse
what are the 4 locations of interatrial septal defects
- ostium primum ASD
- ostium secundum ASD
- patent foramen ovale (fossa ovalis)
- sinus venosus ASD
- superior (SVC), inferior (IVC)
what is the most common type of ASD
- ostium secundum
what are the 4 stages to ventricular septal formation
stage one = trabecular IVS
stage two = TO and MO formation
stage three = truncus formation
stage four = membranous septum
stage one of ventricular septal formation : trabecular IVS - how are the RV and LV formed
- the bulbus Cordis becomes the RV
- he Primitive Ventricle becomes the LV
stage one of ventricular septal formation : trabecular IVS - where is the origin of the trabecular IVS (muscular) and are does it travel
- grows from apex to base
- stops part way between the ventricles
- this allows blood flow from other ventricles to exit the truncus arteriosus through the inter ventricular foramen
stage two of ventricular septal formation: TO and MO formation - how is the TO and MO formed
- truncus arteriosus and AV cancan move more centrally
- tricuspid and mitral orifices form
stage two of ventricular septal formation: TO and MO formation - how is the rest of the IVS formed
- growth of the inlet portion of the inter ventricular septum
- fusion of the inlet and trabecular IVS form the IVS
stage three of ventricular septal formation: truncus formation - how are the two great vessels formed from the truncus arteriosis
- truncus arteriosus divides with formation of conotruncal septum to form the proximal aorta and pulmonary artery
- septum then forms in spiral fashion
hoe is the aortic and pulmonary root form
- conus cordis divides outflow tract into right and left
- ## two swelling in the truncus arteriosus begin to grow which form a septum
Step four of ventricular septum formation: membraneous septum
- once truncus arteriosus divides, the membranous IVS forms to complete the right heart and left heart separation sequence
what are the 4 typical locations of VSD and which is most common
- membraneous MOST COMMON
- inlet VSD
- muscular VSD
- outlet VSD
what are the 2 sub locations of outlet VSDs and what is there location
- supracristal = above crista supraventricularis ridge (seen close to PV in SAX)
- infracristal = below crista supraventricularis ridge (seen directly anterior to AO valve in SAX)
what type of CHD is a VSD
- acyanotic
- not bad enough to cause serious hypoxia
which way is the blood shunted with a VSD
- left heart to right heart
what is the tool used to assess any shunt
- Qp/Qs
where and what views would we see a perimembraneous VSD
- PLAX,
- PSAX at AO valve 9-12 O’clock
- AP 5
- subcostal 5
where and what views would we see a muscular/trabecular VSD
- PLAX
- PSAX (LV-pap level & apex)
- AP 4 &5
- subcostal 4 & 5
- SAX views
where and what views would we see a outlet VSD
- PLAX
- PSAX (ao valve 12-3 o’clock)
- subcostal 5
- SAX of AO
where and what views would we see an inlet VSD
- PSAX (MV and LV at pap level)
- AP 4
- subcostal 4
what is Qp
- volume of blood going to lungs
what si Qs
- volume of blood going to aorta
how is Qp calculated
- from pulmonary arterial stoke volume
- RVOT diameter and VTI of RVOT flow
how is Qs calculated
- LVOT diameter and VTI of LVOT
what is the normal Qp/Qs
1:1
what Qp/Qs indicated a hemodynamically significant shunt
- ratio greater than 1.5:1
what Qp/Qs corresponds to a small shunt and what is the treatment
- 1 - 1.5: 1
- none or septal occlude device
what Qp/Qs corresponds to a moderate shunt and what is the treatment
- 1.5-2.0: 1
- septal occluder device or septal patch
what Qp/Qs corresponds to a large shunt and what is the treatment
- > 2.0:1
- foetal patch
what is the flow through the heart with an ASD
- flow enters RA from the LA through the ASD
- flow to the lungs through the TV and RVOT flow in increased
- flow entering the LA through the pulmonary veins is increased
what is flow through the heart with a VSD
- flow from the LV enters the RV through the VSD
- RVOT flow in increased
- flow to the lungs is increased
- flow to the pulmonary veins and MV is increased
- may lead to the dilation of RV and LA
how to calculate Qp
- measure RVOT diameter \+ during systole, <5mm from pulmonary annulus, inner to inner - CSA = 0.785 x d^2 - trace RVOT VTI - Qp = CSA x VTI
how to calculate Qs
- measure LVOT diameter \+ during systole \+ < 5mm from annulus - CSA = 0.785 x d^2 - trave LVOT VTI - Qs = CSA x VTI
what rules is changed when obtaining a Qp and Qs with a PDA
- Qp derived from LVOT
- Qs derived from RVOT
what is the flow through the heart with PDA flow
- flow shunts from descending ao to the pulmonary artery
- flow to the lungs is increased
- flow the pulmonary veins, LA, MV, LV, LVOT increased
- entire left heart has increased volume
how to calculate RVSP in presence of VSD
RVSP = BP systolic - 4 x (Vmax VSD)^2
what is eisenmengers syndrome
- shunt direction is switched to right to left
- caused by large shunt with high volume to lungs causing lung damage increasing pulmonary resisitncae
what are 6 complications of eisenmengers syndrome
- CHF
- early death
- brain abscess
- SBE
- pulmonary infarction
- pregnancy contraindicated
how do we report intracardiac shunts
- segmental approach to describe VSD
what are the 2 function of the endocardial cushions
- divide AV canal into 2 atrioventricular orifices
- assist in closure of ostium primum portion of IAS and membranous portion of IVS
what are the different endocardial cushions
- 2 medial
- 2 lateral
what do the 2 medial endocardial cushions form
- septal leaflet of tricuspid valve
- anterior leaflet of mitral valve and portion of inflow perimembranous IVS
what do the 2 lateral endocardial cushions form
- anterior and posterior TV leaflets
- posterior leaflet of mitral valve
how many sets of aortic arches are formed in the fetus
6
which aortic arch develops into the adult aorta
4th
what two structures are the other aortic arches formed
- carotid artery
- ductus arteriosus
how are the AV valves formed
- from portion of the AV canal
- connective tissue
- endocardial lateral cushions
how are the semilunar valves formed
- from truncus arteriosus
- swelling of tissue forms vessels/valves
what is the normal route of oxygenated blood to the fetal heart
- umbilical vein > DV > IVC > RA
- eustacian valve directs most of the blood through foramen ovale
what ar ether 2 possible paths of oxygenated flow one blood reaches the fetal heart
1) RA > LA > … LA > LV > AO
2) RA > TV > RV > PA > ductus arteriosus > AO
what six events happen at birth in the fetal heart
- umbilical vein closes
- ducts arteriosus closes - becomes ligamnetum arteriosum
- foramen ovale closes - become fossa ovalis
- RV and pulmonary artery walls decrease in thickness (pressure decreases)
- LV walls increase in thickness (pressure increase)
- ductus venosus closes - becomes ligamentum venosum
