Week 10 Heart murmur Flashcards
What type of fetal cells form the heart tube?
Mesodermal cells
How does the fetal heart form?
Mesodermal cells form two heart tubes connected by an arch.
The two tubes merge into one heart tube.
The heart tube folds and the internal structure separates into four chambers.
When do the cardiac precursor cells condense to form 2 endocardial tubes?
Day 19
When does the trilaminar embryo fold laterally, fusing the two endocardial tubes into a single heart tube?
Day 21
When does the heart tube begin to loop?
Days 23-28
When does the septum primum begin to grow and the atrioventricular septum begin to form?
Day 28
When does the aorticopulmonary septum begin to form?
Day 35
When is the atrioventricular septum complete?
Day 42
When is the foramen primum complete?
Day 46
When does the aorticopulmonary septum form?
Day 35-56
Which embryonic germ layer do the cardiac precursor cells form in?
Splanchnic mesoderm
What does the ectoderm give rise to?
CNS and neural tissues
Skin epidermis
Skeletal tissues
Teeth
What does the mesoderm give rise to?
Muscle, bones, cartilage
Blood cells and vessels
Skin dermis
Kidneys, ureters, genital system
Cardiac tissue
What does the endoderm give rise to?
GI tract lining
Liver, pancreas (except islets)
Respiratory tract lining
Bladder
What causes the positioning of the heart to bulge further into the future pericardial cavity?
Cephalocaudal folding
Day 19-21
When does the heart begin to beat?
Day 22
Discuss the aortic sac
Superior arms of the heart tube.
Gives rise to:
Ascending aorta
Brachiocephalic artery
Pharyngeal arch arteries
Discuss the bulbus cordis
Below the aortic sac.
Made up of:
Truncus Arteriosus which becomes the aorta and pulmonary trunk
Bulbus Cordis which becomes the right and left ventricle outflow
Discuss the primitive ventricle.
Middle area of the heart tube.
Becomes the right and left ventricles.
Discuss the primitive atrium.
Below the primitive ventricle.
Becomes:
Left auricle and atrium
Right auricle and atrium - rough part
Discuss the sinus venosus.
Bottom portion, including the arms of the heart tube.
Becomes:
Right atrium - smooth part
Coronary sinus
Part of SVC
When does the heart tube begin to loop and when is it complete?
Day 23-28
Discuss the process of heart looping.
Aortic sac: remains fixed during looping
Bulbus cordis: moves inferior, anterior, and to the right.
Primitive ventricle: moves to the left
Primitive atrium: moves posterior and superior
Sinus Venosus: moves posterior and superior
What are the 5 septa of the fetal heart?
- Atrioventricular septum
- Foramen ovale
- Interventricular septum (muscular portion)
- Aorticopulmonary septum
- Interventricular septum (membranous portion)
Endocardial cushions
Swellings/thickenings of migrated cells that will fuse to form septa and valves.
Located on all four sides of the heart, at the level of where the atrioventricular septum will be.
Invaginate to form the beginnings of atrioventricular septums, dividing the heart into atria and ventricles and right and left.
How is the atrioventricular septum formed?
Day 28-42
Dorsal and ventral endocardial cushions grow towards each other and fuse.
Discuss formation of the foramen ovale.
Day 28-46.
Day 28-35 Septum Primum forms from the dorsal part of the roof of the primitive atrium and grows towards the fusing endocardial cushions. Septum primum has holes to allow blood to pass from R to L
Foramen Secundum
Holes at the top of the septum primum that eventually coalesce to form the foramen secundum.
Septum Secundum & Foramen ovale
After the foramen secundum forms in the septum primum, the septum secundum grows down from the ventral part of the roof of the right atrium.
It does not fuse with the endocardial cushions.
This gap is the foramen ovale.
The pressures at birth force the septum secundum against the septum primum and closes the gap of the foramen ovale.
Which septum is movable allowing blood flow between the R and L atria?
The Septum primum is flexible.
The Septum secundum is sturdy, providing structural support.
Discuss the formation of the muscular interventricular septum.
Day 28-46
Grows upward from the floor of the primitive ventricle towards the atrioventricular septum.
Gap at the top is the interventricular foramen, allowing blood flow from R to L ventricle.
Discuss the formation of the aorta and pulmonary trunks.
Ridges form from the bulbus cordis and truncus arteriosus.
These ridges widen and fuse while creating a spiral separation.
One side is the aorta and the other is the pulmonary trunk.
List 5 unique aspects of the fetal circulatory system at term.
- Umbilical vein
- Ductus venosus
- Foramen ovale
- Ductus arteriosus
- Umbilical artery
Discuss the formation of the interventricular septum, membranous portion.
Day 42-56
The aorticopulmonary septum grows downward to the muscular interventricular septum and merges with the atrioventricular outgrowth.
What are the benefits of delayed cord clamping?
Increased iron, decreased anemia.
Increased blood volume.
Increased stem cells to newborn.
(Increased fine motor and social skills at age 4)
Decreases risk of newborn/birther separation.
Decreased risk of intraventricular hemorrhage in preemies.
Decreased risk of necrotising enterocolitis in preemies.
Discuss the closure of the foramen ovale.
- First breath, lungs expand.
- Capillary bed in lungs expands, decreasing vascular resistance in the lungs. More blood is enters the pulmonary trunk.
- Flow from lungs to L atria increases, pressure in L atria is greater then pressure in R and pushes against septum primum, closing foramen ovale.
Patent Foramen Ovale
Foramen ovale does not close.
In most people does not cause serious complications, but may need surgery if severity is high.
Discuss the closure of the Ductus Arteriosus.
1.Drop in prostaglandins from placenta. Protaglandins helped to keep the ductus open.
2. Increase in newborn pO2 initiates constriction of ductus arteriosus tissue.
Becomes ligamentum arteriosum.
With closure, output from R vent goes to lungs and output from L vent goes to systemic circ.
Discuss the closure of the umbilical vein and ductus venosus.
Cord is clamped and no blood enters umbilical vein.
Residual blood in vein clots.
Umbilical vein becomes round ligament of liver.
Ductus venosus loses blood flow and closes.
Ductus venosus becomes ligamentum venosum.
Discuss the obliteration of the umbilical arteries.
Arteries obliterate and can be seen as medial umbilical ligaments on the anterior abdominal wall.
What are the 3 main epicardial coronary arteries and their branches?
Right coronary artery - acute marginal & posterior descending artery.
Left main coronary artery:
Left anterior descending artery - diagonal branches.
Left circumflex artery - obtuse marginal branches.
What is the time interval between S1 and S2?
Ventricular systole
What results in abnormal heart sounds?
Abnormal valve movements.
Abnormal cardiac movements.
S1 heart sound
AV valves closing
S2 heart sound
Semilunar valves closing
Should be able to hear both
What is the time interval between S2 and S1?
Diastole
S3
Occurs in early diastole.
Occurs in the prescence of a volume overloaded ventricle.
Rapid cessation of blood flow in early diastole results in an abnormal heart sound.
S4
Occurs in late diastole.
Occurs in the presence of a pressure overloaded ventricle.
Extra pressure and volume from atrial contraction into a stiff ventricle results in an abnormal heart sound.
Ejection click
Abnormal opening of a semilunar valve.
Most commonly bicuspid aortic valve.
Opening snap
Rheumatic mitral valve stenosis
Which side of the heart has lower pressures?
Right.
The pulmonary circulation is a low resistance circulation. The pressure from the right side of the heart is lower even though the volumes are the same.
The right ventricle is thinner walled.
What are the 2 components of the S1 sound?
Mitral valve closure (M1)
Tricuspid valve closure (T1)
Timing is almost simultaneous. Won’t hear them separately in a healthy heart.
What are the 2 components of the S2 sound?
Aortic semilunar valve (A2)
Pulmonary semilunar valve (P2)
Can hear these separately, called S2 split.
Why do the valve closures on the left happen earlier than the right?
Because the right side is lower pressure than the left.
Discuss inspiration and cardiac blood flow
- Negative intrathoracic pressure - decreases pulmonary resistance - volume of blood returning to R hear increases - more blood stays in the pulmonary vasculature.
- R side pressure decreases.
- L side pressure also decreases d/t blood staying in the pulmonary vasculature.
- L heart valves close earlier d/t decreased pressure.
- Volume of blood through the R side of the heart increases d/t decreased pulmonary vascular resistance, resulting in later closure of valves.
RESULT: On inspiration, the S2 split increases.
Heart murmur
Increased or turbulent blood flow.
Flow must be dependent on a pressure gradient. No pressure, no flow, no murmur.
When are increased flow states seen in the heart?
Increased flow through normal structures:
Anemia, pregnancy, high metabolic states.
Turbulent flow through narrow orifices:
Narrowed valved, incompetent valve, shunt (septal defect).
Flow into a larger chamber:
Aortic aneurysm.
The higher the flow or turbulence = more prominent murmer.
P wave
Atrial contraction
Increases LA pressure - results in atrial A wave with subsequent X descent.
QRS complex
Ventricular contraction
Isovolumetric contraction time (IVCT)
Period of time during which the LV pressure increases but the LV volume stays the same (both valves are closed).
T wave
Ventricular relaxation.
Late systole.
Mitral valve closed but blood still flows into the LA, increasing LA pressure, contributing to the V wave.
Isovolumetric relaxation time (IVRT)
LV pressure decreases but the LV volume remains constant (aortic and mitral valves are closed).
How are aortic pressures reported?
Systolic/diastolic/(mean)
How are LV pressures reported?
Systolic/diastolic/(LVDEP)
How are LA pressures reported?
A/VI/(mean)
Which heart valves are septophilic?
Septophobic?
Septophilic: Tricuspid (RAV) - chordae can insert directly into the interventricular septum.
Septophobic: Mitral valve.
Situs ambiguous
An abnormal arrangement that can be quite variable
Situs solitus
Normal arrangement of the organs within the body
Situs inversus
A mirror image of the normal arrangement of organs within the body.
What chamber gives rise to an infundibulum?
R. ventricle
What is the most common ASD?
The secundum atrial septal defect.
What is the difference in the right atrium as compared to the left?
The right atrium is characterized by certain features including the broad based triangular shaped appendage with trabeculations that extend beyond the atrium.
Discuss the blood flow in an ASD.
Hole in the atrial septum allows for mixing of blue and pink blood.
Pressure in higher in the L atrium, forcing pink blood into the R atrium through the hole.
R atrium dilates to accommodate increased volume.
R ventricle and pulmonary artery also dilate.
Blood flow increased to the lungs.
Acyanotic.
How are ASDs repaired?
Surgical patch
Catheterization using a device.
Overtime the heart tissue grows over the patch.
What are the features of Tetralogy of Fallot
Cyanotic CHD.
4 features:
VSD
Overriding aorta
Pulmonary stenosis
RV hypertrophy.
**Anterior deviation of the infundibular septum.
Varying levels of cyanosis.
Prone to tet spells.
Blood flow patterns of Tetralogy of Fallot.
Pink blood enters L atrium and then into L ventricle.
Blood then goes in two directions; into aorta or through VSD into R ventricle.
Blood pumped from R vent through narrow RVOT and small PA.
Blue blood enters R atrium then into R vent.
Blue blood shunts to L ventricle through VSD and out the aorta.
Varying levels of cyanosis occur.
How is Tetralogy of Fallot managed?
Most common:
VSD patch so that hole is fixed and aorta arises from L vent at 6 months.
Open the RVOT with monocusp transannular patch - needs future surgeries.
Discuss TGA
Circulation is connected in parallel rather than series.
PA arises from L vent.
Aorta arises from R vent.
Mixing of blood occurs from ASD, VSD, ductus arteriosus.
Cyanotic.
Management of TGA
**PGE1 to keep ductus arteriosus open.
Arterial switch performed.
Coarctation of the aorta
Characteristic narrowing of the aorta the results in a decrease amount of pink blood to the the body.
Left-sided obstructive lesion that can present at different times in life.
Critical presents in neonatal period.
Non-critical presents later with hypertension and reduced femoral pulses.
BP above coarctation is higher than normal.
BP below coarctation is lower than normal.
Repair of coarctation of the aorta.
Critical: PGE1 to keep DA open.
Cardiac catheterization.
Surgical repair.
Truncus arteriosus
Single arterial vessel gives rise to systemic, pulmonary, and coronary circulations.
Single semilunar valve present.
Blood flow depends on valve structure; stenosis or regurgitation.
Blood flow also dependant on vascular resistance, will flow where decreased resistance.
Coronary perfusion compromised if truncal valve regurgitation in diastole.
Management of truncus arteriosus.
VSD closed with a patch allowing the truncal valve to originate in the L vent.
Valve repair may be needed.
Valved conduit created for R vent to PA.
Hypoplastic left heart syndrome
Most severe form of left sided obstructive lesions.
Critically underdeveloped L side of heart, only R ventricle is functional.
Cyanotic.
Discuss blood flow in HLHS
Blood returns to L atrium from PV.
Mitral valve stenosis d/n allow flow into LVent.
Patent foramen ovale allows for L to R atrial shunt.
Mixed blood passes into R vent.
Mixed blood goes to lungs or through ductus arteriosus to aorta.
