Paediatrics Flashcards
What is the ductus venosus?
This shunt connects the umbilical vein to the inferior vena cava and allows blood to bypass the liver.
What is the foramen ovale?
This shunt connects the right atrium with the left atrium and allows blood to bypass the right ventricle and pulmonary circulation.
What is the ductus arteriosus?
This shunt connects the pulmonary artery with the aorta and allows blood to bypass the pulmonary circulation.
How does the foramen ovale close?
The first breaths the baby takes expands the alveoli, decreasing the pulmonary vascular resistance. The decrease in pulmonary vascular resistance causes a fall in pressure in the right atrium. At this point the left atrial pressure is greater than the right atrial pressure, which squashes the atrial septum to cause functional closure of the foramen ovale, similar to a closed valve with nothing flowing through it. This then gets sealed shut structurally after a few weeks and becomes the fossa ovalis.
How does ductus arteriosus close?
Prostaglandins are required to keep the ductus arteriosus open. Increased blood oxygenation causes a drop in circulating prostaglandins. This causes closure of the ductus arteriosus, which becomes the ligamentum arteriosum.
How does ductus venosus close?
Immediately after birth the ductus venosus stops functioning because the umbilical cord is clamped and there is no flow in the umbilical veins. The ductus venosus structurally closes a few days later and becomes the ligamentum venosum.
What are flow murmurs?
Innocent murmurs are also known as flow murmurs. They are very common in children. They are caused by fast blood flow through various areas of the heart during systole.
What are flow murmurs like?
Soft
Short
Systolic
Symptomless
Situation dependent, particularly if the murmur gets quieter with standing or only appears when the child is unwell or feverish
When might we refer a paediatric murmur?
Murmur louder than 2/6
Diastolic murmurs
Louder on standing
Other symptoms such as failure to thrive, feeding difficulty, cyanosis or shortness of breath
Give three causes of cyanotic heart disease
Heart defects that can cause a right-to-left shunt, and therefore cyanotic heart disease, are:
Ventricular septal defect (VSD)
Atrial septal defect (ASD)
Patent ductus arteriosus (PDA)
Transposition of the great arteries
What is Eisenmenger syndrome?
Patients with a VSD, ASD or PDA are usually not cyanotic. This is because the pressure in the left side of the heart is much greater than the right side, and blood will flow from the area of high pressure to the area of low pressure. This prevents a right-to-left shunt. If the pulmonary pressure increases beyond the systemic pressure blood will start to flow from right-to-left across the defect, causing cyanosis.
Will patients with transposition of the great arteries be cyanotic?
Patients with transposition of the great arteries will always have cyanosis because the right side of the heart pumps blood directly into the aorta and systemic circulation.
How does patent ductus arteriosus present OE?
More significant PDAs cause a normal first heart sound with a continuous crescendo-decrescendo “machinery” murmur that may continue during the second heart sound, making the second heart sound difficult to hear.
What is the pathophysiology in PDA?
The pressure in the aorta is higher than that in the pulmonary vessels, so blood flows from the aorta to the pulmonary artery. This creates a left to right shunt where blood from the left side of the heart crosses to the circulation from the right side. This increases the pressure in the pulmonary vessels causing pulmonary hypertension, leading to right sided heart strain as the right ventricle struggles to contract against the increased resistance. Pulmonary hypertension and right sided heart strain lead to right ventricular hypertrophy. The increased blood flowing through the pulmonary vessels and returning to the left side of the heart leads to left ventricular hypertrophy.
Give a complication of atrial septal defect
Stroke (clot moves from RA to LA)
May present with a DVT that develops a large stroke == small ASD
Give three causes of pan-systolic murmur
When you hear a pan-systolic murmur it is worth giving your top differential but also mention the other causes of this type of murmur. The causes of a pan-systolic murmur are ventricular septal defect, mitral regurgitation and tricuspid regurgitation.
How do we treat ASDs/VSDs?
Referral to paediatric cardiologist
VSDs can be corrected surgically using a transvenous catheter closure via the femoral vein or open heart surgery.
What is coarctation of the aorta? What usually causes it?
Coarctation of the aorta is a congenital condition where there is narrowing of the aortic arch, usually around the ductus arteriosus. The severity of the coarctation (or narrowing) can vary from mild to severe. It is often associated with an underlying genetic condition, particularly Turners syndrome.
How do we manage severe coarctation of the aorta?
In cases of critical coarctation where there is a risk of heart failure and death shortly after birth Prostaglandin E is used keep the ductus arteriosus open while waiting for surgery. This allows some blood flow flow through the ductus arteriosus into the systemic circulation distal to the coarctation. Surgery is then performed to correct the coarctation and to ligate the ductus arteriosus.
What is tetralogy of fallot?
Ventricular septal defect (VSD)
Overriding aorta
Pulmonary valve stenosis
Right ventricular hypertrophy
What might be seen on CXR in ToF?
A chest xray may show the characteristic “boot shaped” heart due to right ventricular thickening. This not particularly useful diagnostically except during medical exams.
What are tet spells?
“Tet Spells” are intermittent symptomatic periods where the right to left shunt becomes temporarily worsened, precipitating a cyanotic episode. This happens when the pulmonary vascular resistance increases or the systemic resistance decreases. For example, if the child is physically exerting themselves they are generating a lot of carbon dioxide. Carbon dioxide is a vasodilator that causes systemic vasodilation and therefore reduces the systemic vascular resistance. Blood flow will choose the path of least resistance, so blood will be pumped from the right ventricle to the aorta rather than the pulmonary vessels, bypassing the lungs.
How do we manage ToF?
In neonates, a prostaglandin infusion can be used to maintain the ductus arteriosus. This allows blood to flow from the aorta back to the pulmonary arteries.
Total surgical repair by open heart surgery is the definitive treatment, however mortality from surgery is around 5%.
Prognosis depends on the severity, however it is poor without treatment. With corrective surgery, 90% of patients will live into adulthood.
What is Ebstein’s anomaly?
Ebstein’s anomaly is a congenital heart condition where the tricuspid valve is set lower in the right side of the heart (towards the apex), causing a bigger right atrium and a smaller right ventricle. This leads to poor flow from the right atrium to the right ventricle, and therefore poor flow to the pulmonary vessels. It is often associated with a right to left shunt across the atria via an atrial septal defect. When this happens blood bypasses the lungs, leading to cyanosis. It is also associated with Wolff-Parkinson-White syndrome.