Cardio Flashcards
How does the fetal circulation work?
Fetus receives oxygen and nutrients and disposes of waste via the placenta, bypassing the lungs
How does the fetal circulation bypass the lungs?
3 fetal shunts
What are the 3 fetal shunts?
Ductus venosus
Foramen ovale
Ductus arteriosus
What does the ductus venosus allow blood to bypass in the fetus?
The liver
What does the ductus venosus connect?
The umbilical vein and inferior vena cava
What does the foramen ovale allow the fetal blood to bypass?
The right ventricle and pulmonary circulation
What does the foramen ovale connect?
The right and left atria
What does the ductus arteriosus allow the fetal circulation to bypass?
The pulmonary circulation
What does the ductus arteriosus connect?
The pulmonary artery and aorta
From the umbilical vein, outline the passage of blood in the fetal circulation:
Placenta–> Umbilical vein–> Ductus venosus–> IVC–> RA–> (Foramen ovale–> Left atrium–> Left ventricle)/ (Right ventricle–> Pulmonary artery–> Ductus arteriosus)–> Aorta–> Internal iliac arteries–> Umbilical arteries–> Placenta
What happens to the pulmonary vascular resistance with the first breath and why?
The first breath expands the alveoli, decreasing the pulmonary vascular resistance
What does the decrease in pulmonary vascular resistance do to the pressure in the right atrium?
Causes it to fall
What does the fall in RA pressure on the first breath result in?
The left atrial pressure becomes greater than the RA, squashing the atrial septum and causing functional closure of the foramen ovale.
Outline the physiology of the closure of the foramen ovale?
On the first breath, the alveoli expand, reducing the pulmonary vascular resistance. This in turn reduces the RA pressure, meaning the LA pressure is greater, squeezing the septum and causing the foramen to close
What does the foramen ovale become after birth and how long does it take to reach this point?
It gets sealed shut after a few weeks to become the fossa ovalis
What causes the closure of the ductus arteriosus at birth?
Increased blood oxygenation causes a drop in circulating prostaglandins which are needed to keep the ductus arteriosus open. This causes its closure.
What does the ductus arteriosus become at birth?
The ligamentum arteriosum
Why does the ductus venosus stop functioning immediately after birth?
Because the umbilical cord is clamped and there is no flow in the umbilical veins
What does the ductus venosum become?
Ligamentum venosum
What are the most common kind of heart murmurs in children?
Innocent murmurs
What are innocent murmurs also known as?
Flow murmurs
What causes flow murmurs?
Fast blood flow through the heart during systole
What are the typical features of innocent murmurs?
Soft Short Systolic Symptomless Situation dependent
How might a situation dependent murmur change?
Quieter on standing
Only appear when the child is unwell/ feverish
What features of a murmur would prompt further investigations and referral to paediatric cardiologist?
Murmur louder than 2/6
Diastolic murmurs
Louder on standing
Other symptoms (e.g. failure to thrice, feeding difficulty, cyanosis, SOB)
What are the key investigations to establish the cause of a murmur and rule out abnormalities?
ECG
CXR
Echo
What is S1?
The first heart sound
What causes S1?
The closing of the atrioventricular valces and the start of ventricular contraction
What are the atrioventricular valves?
Mitral and tricuspid
What is S2?
The second heart sound
What causes S2?
The closing of the semilunar valves
What are the semilunar valves?
Pulmonary and aortic valves
Are S3 and S4 normal?
Always pathological
What are the differentials of a pan-systolic murmur in children?
Mitral regurgitation
Tricuspid regurgitation
Ventricular septal defect
Where would a ventricular septal defect be heard?
Left lower sternal border
What are the differentials of an ejection-systolic murmur in children?
Aortic stenosis
Pulmonary stenosis
Hypertrophic obstructive cardiomyopathy
Where would hypertrophic obstructive cardiomyopathy be heard?
Fourth intercostal space, left sternal border
Where do you listen for the aortic valve?
2nd intercostal space, right sternal border
Where do you listen for the pulmonary valve?
2nd intercostal space, left sternal border
Where do you listen for the tricuspid valve?
5th IC space, left sternal border
Where do you listen for the mitral valve?
5th IC space, midclavicular line
Why is the second heart sound split into two?
Due to the negative intra-thoracic pressure on inspiration, the right side of the heart fills up faster than the left. This increased volume means it takes longer for the right ventricle to empty during systole, causing a delay in the pulmonary valve closing compared to the aortic valve.
What is PDA?
Patent ductus arteriosus
What is the action of the ductus arteriosus?
Shunts blood from the pulmonary artery straight to the aorta, bypassing the lungs
How long after birth should the ductus arteriosus stop functioning and after how long will it close completely?
Stops functioning within 1-3 days
Closes completely in first 2-3 weeks
What are the potential causes of PDA?
Unknown-
Genetic, maternal infections
What is a key risk factor for developing PDA?
Prematurity
Are PDA’s always symptomatic?
No, may be asymptomatic and cause no functional problems and close spontaneously
If patients with PDA are asymptomatic throughout childhood, how may they present in adulthood?
With signs of heart failure
What kind of shunt is created in PDA and why?
Pressure in aorta is higher than pulmonary vessels, so blood flows from left to right side of circulation.
What does the increased pressure in the pulmonary vessels cause?
Pulmonary hypertension, leading to right sided heart strain.
Why do you get right ventricular hypertrophy in PDA?
Due to the pulmonary hypertension causing right sided heart strain
Why do you also get left ventricular hypertrophy in PDA?
Due to the increased blood flowing through the pulmonary vessels and returning to the left side of the heart
How might PDA present?
Murmur at newborn examination SOB Difficulty feeding Poor weight gain LRTI
What kind of murmur might you hear with more severe PDA?
Normal first heart sound, with continuous crescendo-decrescendo ‘machinery’ murmur that may continue during second heart sound
How is a PDA diagnosis confirmed?
Echocardiogram
Doppler flow studies
How is PDA managed?
Patients monitored until 1 year using echo’s.
If not closed, trans-catheter or surgical closure can be performed
Why are patients with PDA monitored for the first year of life?
Because it may spontaneously close itself
What is an atrial septal defect?
Hole in the septum allowing blood to flow between the two atria
What happens to the atria, septum during development of the fetus?
Atria begin connected, then septum primum and septum secondum grow downwards and fuse with endocardial cushion to separate them.
Where is the foramen ovale?
In the second secondum between the atria
What happens to the heart circulation in atrial septal defects?
Blood shunts from the left to right atrium due to the higher pressure in the LA
Does the patient become cyanotic with atrial septal defects?
No, the blood continues to flow to the pulmonary vessels and lungs to get oxygenated
What does the increased flow to the right side of the heart in ASD’s lead to?
Right sided overload
Right heart strain
Can lead to right heart failure and pulmonary hyptersion
What can pulmonary hypertension eventually lead to?
Eisenmenger syndrome
What is Eisenmenger syndrome?
Where the pulmonary pressure is greater than the systemic pressure, so the shunt reverses and forms a right to left shunt across the ASD
What are the different types of atrial septal defect?
Ostium secondum
Patent foramen ovale
Ostium primum
What is the most common ASD?
Ostium secondum
What is ostium secondum
Where the septum secondum fails to close, leaving a hole in the wall
What is ostium primum?
Where the septum primum fails to fully close, leaving a hole in the wall
What does ostium primum usually lead to?
Atrioventricular valve defects
What are the key complications of ASD?
VTE–> Stroke
AF
Pulmonary hypertension–> Right sided heart failure
Eisenmenger syndrome
Why is ASD a cause of stroke in patients with a DVT?
In ASD the clot is able to travel from the right to the left atrium and up to the brain, whereas it would usually cause a pulmonary embolism
What does a murmur sound like in ASD?
Mid-systolic, crescendo-decrescendo murmur, loudest at upper left sternal border, with fixed split second heart sound
What is a fixed split heart sound?
When the split between the aortic and pulmonary valves closing doesn’t change with inspiration or expiration
Why do you get a fixed split heart sound in ASD?
Because blood is flowing from the left atrium to the right atrium, increasing the volume of blood that the right ventricle has to empty before the pulmonary valve can close
When are ASD’s usually picked up?
On antenatal scans or newborn examinations
How may ASD present in childhood?
SOB
Difficulty feeding
Poor weight gain
Lower respiratory tract infections