Cardiovascular Flashcards
When does the cardiovascular system begin to develop?
End of the 3rd week
When does the heart start to beat?
Beginning of the 4th week
What supplies the foetus with oxygen?
Umbilical vein which emerges from the placenta
This carries oxygen rich blood from the mother to the inferior vena cava via the ductus venosus to the fetal heart
What carries oxygen-depleted blood from fetus to the placenta?
Two umbilical arteries
There are remnants of the umbilical arteries in the adult
What are the three shunts in fetal circulation?
1) Foramen ovale
2) Ductus arteriosus
3) Ductus venosus
Which shunts are critical during fetal life when the lungs are compressed, filled with amniotic fluid and non functional, and gas exchange is provided by the placenta?
Foramen ovale
Ductus arteriosus
Close shortly after birth when the newborn begins to breathe
What is the foramen ovale? Which way is the shunt?
An opening in the interatrial septum that allows blood to flow from RA to LA, hence bypassing the pulmonary circulation
A valve associated with this opening prevents backflow of blood during the foetal period
When does the foramen ovale close?
When the newborn begins to breathe and blood pressure in the atria increases
There is an increase in pressure in left side because there is a decrease in pulmonary resistance when baby takes their first breath - also the cold and the clamping of the cord causes a decrease in systemic resistance leading to a reactionary increase in BP
What is the ductus arteriosus? Which way is the shunt?
A short, muscular vessel that connects the pulmonary artery to the aorta
Most of the blood pumped from RV to pulmonary trunk is thus diverted to the aorta
Therefore, only enough blood reaches the foetal lungs to maintain the developing lung tissue
What happens when the ductus arteriosus closes?
When the newborn takes the first breath, pressure within lungs drops dramatically, and both the lungs and pulmonary vessels expand
As the amount of oxygen increases, the smooth muscles in the wall of the ductus arteriosus constrct, sealing off the passage
Eventually the muscular and endothelial components of the ductus arteriosus degenerate, leaving only the connective tissue component of the ligamentum arteriosum
What is the ductus venosus?
A temporary blood vessel that branches from the umbilical vein allowing much of the freshly oxygenated blood to bypass the liver and go directly to the fetal heart
When does the ductus venosus close?
Closes slowly during the first few weeks of infancy and degenerates to become the ligamentum venosum
What are heart murmurs?
Caused by turbulence of blood flow and my be innocent or pathological
How are heart murmurs classified?
Graded 1-6
Grade 1:
- Murmur barely audible
- No thrill
Grade 2:
- Murmur soft and variable in nature
- No thrill
Grade 3:
- Murmur easily heard
- No thrill
Grade 4:
- Loud murmur
- Thrill present
Grade 5:
- Very loud murmur
- Thrill present
Grade 6:
- Murmur heart without stethoscope
- Thrill present
What should be included when examining the heart of a child with a suspected murmur?
Check for radiation over the axilla, carotid arteries and the back
Listen in inspiration and expiration
Listen with the child lying down and standing up
Turn the child on the left side
Which types of murmur (systolic or diastolic) are always pathological?
Diastolic
What causes a diastolic murmur? (3)
1) Increased blood flow through a normal atrioventricular valve
2) Stenosis of a AV valve
3) Incompetence of the pulmonary or aortic vessels
What can how can systolic murmurs be described? (2)
Ejection systolic - diamond shaped in intensity
Pansystolic
What characteristics should be used to describe a murmur (5)
1) Systolic or diastolic
2) Character = blowing or harsh
3) Grade
4) Site of maximum intensity
5) Radiation
What is an innocent murmur?
Has no clinical significance
May be more apparent at times of illness or fever
How does an innocent murmur sound?
Musical
When is an innocent murmur heard?
Systole
Is there radiation in an innocent murmur?
No
Is an innocent murmur variable?
Yes - varies with posture and position
When is a patholologic murmur heard?
Diastole
Pansystolic
Describe how a pathological murmur sounds
Harsh or long
Does a pathological murmur radiate or have a thrill?
Yes may do either
What else is often associated with pathological murmurs?
Cardiac signs / symptoms
In which direction are shunts more common?
Left to right shunt
What can occur if there is a large, considerable volume is shunted left to right?
Hypertrophy
Ventricular dilatation
Congestive cardiac failure
= child presents with breathlessness but is not cyanosed
What is the most common congenital heart defect?
VSD
32% of CHD
Can be membranous or muscular
How may a VSD present?
If small = child may be asymptomatic
If large = breathlessness on feeding and crying, poor growth and recurrent chest infections
May be signs of HF
What may be heard on auscultation of a heart with a VSD?
A harsh, rasping, pansystolic murmur
Heard over lower left sternal border
In large defects = thrill is present and murmur radiates over the whole of chest (parasternal thrill)
Is the loudness of a murmur proportional to the size of the shunt?
No
What can be seen in on a CXR and ECG of a large VSD?
CXR - cardiomegaly and large pulmonary arteries
ECG - biventricular hypertrophy
What is the management of VSD?
Prevention of endocarditis is important - prophylactic abx
Small muscular defects usually close spontaneously
Large membranous defects with cardiac failure are initially managed medically, but surgical treatment may be required
What can happen if VSD are not corrected?
Increased pulmonary blood flow can lead to pulmonary HTN which eventually leads to reversal of the shunt and intractable cyanosis. This is life-threatening
= Eisenmenger’s syndrome
When may an ASD be detected?
Later in childhood - the murmur is soft
Describe the murmur in an ASD and what causes it
Systolic murmur heard in the second left interspace
Due to the high flow across the normal pulmonary valve (not due to flow across the ASD itself)
Second heart sound is widely split and ‘fixed’ (does not wary with respiration)
How may a child with an ASD present?
Breathlessness
Tiredness on exertion
Recurrent chest infections
What is the management of an ASD?
If defect is moderate or large, closure is carried out either by open heart surgery or using a cardiac catheter
What is the prognosis of an ASD?
Usually good
If untreated, can develop cardiac arrhythmias in early adulthood
List 3 innocent murmurs
1) Systolic ejection murmur
2) Pulmonary flow murmur
3) Venous hum
What is a systolic ejection murmur?
Short systolic murmur occurring during ejection and heard along the left sternal edge at the apex
What does a systolic ejection murmur sound like? When is it heard?
Musical - sounds like a tuning fork
Varies in intensity when child changes from lying to sitting, and is intensified by fever, excitement or exercise
What is a pulmonary flow murmur?
Caused by rapid blood flow across a normal pulmonary valve
What does a pulmonary flow murmur sound like? How is it best heard?
A brief, high-pitched blowing murmur, best heard in the second left intercostal space with the child lying down
What is a venous hum?
Caused by flow through the systemic great veins
What does a venous hum sound like? When is it heard?
Blowing, continuous murmur heard at the base of the heart just below the clavicles
Sounds like a soft hum during both systole and diastole
Varies with positioning of the head and disappears when the child lies down
What CHD is associated with down syndrome?
Atrioventricular septal defect (AVSD)
40% of those with Down’s syndrome
Which CHD presents with a collapsing pulse and in is more common in premature infants?
Patent ductus arteriosus
How does a PDA murmur sound?
Pansystolic murmur in neonates
Continuous after 3 months of age
Where does coarctation of the aorta usually occur?
At the origin of the ductus ateriosus
Describe blood flow in coarctation of the aorta
Arteral blood flow bypasses the obstruction, reaching the lower half of the body through collateral vessels which enlarge
= LV hypertrophy - can lead to HF
How may severe coarctation of the aorta present?
Severe cases = baby may collapse at the end of the 1st week of life when ductus ateriosus (through which systemic BF has been maintained) closes
How does coarctation of aorta present?
Systolic murmur heard over left side of chest (esp back)
Disparity in pulses and blood pressure of arms and legs:
- Right brachial and radial pulses are normal, but femoral pulses are absent or weak and delaued
- HTN in right arm but not in legs
What investigations are done for coarctation of aorta?
CXR - LV may be prominent, and rib notching may be seen where enlarged intercostal arteries have eroded underside of rubs
ECG - LV hypertophy
What is the management of coarctation of the aorta?
Surgery to resect narrowed section of the aorta
What is transposition of the great vessels?
Aorta arises from the RV and the pulmonary artery from the LV
What happens to blood flow in transposition of the great vessels?
Mixing of venous and arterial blood occurs through the ductus arterosus and often through a septal defect which accompanies the condition
The less mixing of blood occurs between the two circulations, the more intense cyanosed the baby is
How does transposition of the great vessels present?
Cyanosis (may be hard to spot)
Difficulty establishing feeds
What investigations are done for transposition of the great vessels?
Pulse oximetry = cyanosis
CXR = narrow cardiac pedicle
ECG
What is the long term management of transposition of the great vessels?
Surgery to switch origins of pulmonary artery and aorta
What is the emergency management of a severely cyanosed child with poor systemic circulation in transposition of the great vessels?
Infusion of prostaglandin to maintain ductus arteriosus open
Emergency balloon septostomy to improve mixing of blood in the heart
What is Fallot’s tetralogy?
1) VSD
2) Overriding of the aorta
3) Pulmonary stenosis
4) RV hypertrophy
When does Fallot’s tetralogy present?
Rarely diagnosed in newborn
Presents with cyanosis at 3 months
What is the prognosis of Fallot’s tetralogy?
Good
Treated with surgery
What is a normal resting heart rate for:
1) Newborn
2) 2yrs
3) 4yrs
4) 6yrs+
1) Newborn: 110-150bpm
2) 2yrs: 85-125bpm
3) 4yrs: 75-115bpm
4) 6yrs+: 60-100bpm
What do P waves represent?
Atrial depolarisation
What does a P wave preceding a QRS complex represent?
Sinus rhythm
What does the PR interval represent?
Time taken for the electrical activity to move between the atria and ventricles
What does the QRS complex represent?
Depolarisation of the ventricles
What does the ST segment represent?
Isoelectric lines that represents the time between depolarisation and repolarisation of the ventricles (contraction)
What does the T wave represent?
Ventricular repolarisation
What does the QT interval represent?
Time taken for the ventricles to depolarise and then repolarise
Which chest leads give:
1) Septal view
2) Anterior view
3) Lateral view
4) Inferior
1) Septal view - V1, V2
2) Anterior view - V3, V4
3) Lateral view - I, aVL, V5, V6
4) Inferior view - II, III, aVF
What are some common indications for paediatric ECGs?
1) Syncope, seizures, funny turns
2) Cyanotic episodes
3) Chest pain / exertion symptoms
4) Diagnosis of rheumatic fever, Kawasaki’s disease, pericarditis, myocarditis
5) Arrhythmias
6) CHD
What may happen to the QRS axis in neonates?
Right axis deviation due to relative RVH in neonate
This regresses in first few months of life
Normal QRS varies with ages:
What may happen to T waves in children?
T wave inversion in V1-3 = Juvenile T wave pattern
What happens to the QRS axis with age?
Varies with age
1 week – 1 month: + 110° 1 month – 3 months: + 70° 3 months – 3 years: + 60° Over 3 years: + 60° Adult: + 50°
What ECG features may be normal in children?
1) Faster HR
2) Rightwards QRS axis
3) Marked sinus arrhythmia
4) Short PR and QRS
5) Slightly peaked P waves
6) Slightly long QTc
7) Q waves
Also:
- Dominant R wave in V1
- RSR pattern in V1
