Congenital Heart Defects Flashcards
What is a congenital defect?
People born with abnormality
What is dextrocardia?
Rare condition where heart points to right side of chest instead of left
What could dextrocardia be a result of?
- Abnormal cardiac looping 2. Induced during gastrulation (week 3) when laterality (right and left side) is determined
What other structural defects could isolated dextrocardia be associated with?
Abnormal connections with veins and arteries or abnormal septation of the heart
In a foetus, what is purpose of ductus arteriosus?
Connection between aorta and pulmonary artery (2 vessels leaving heart), allowing blood to bypass lungs as baby receives O2 from mother’s circulation
What causes ductus arteriosus to close after birth? What is purpose of it closing?
Increasing O2 tension and decrease in circulating prostaglandins Blood can then bypass heart and go straight to lungs
What happens if ductus arteriosus fails to close?
Causes too much blood to circulate to baby’s lungs and heart. Oxygenated blood travels back to the lungs, then returns to the heart to be pumped out again. Increase workload of heart.
What can patent ductus arteriosus lead to?
- Pulmonary hypertension 2. Heart failure 3. Ventricular hypertrophy
How can patent ductus arteriosus lead to pulmonary hypertension?
Too much blood circulating through the heart’s main arteries through a patent ductus arteriosus can lead to pulmonary hypertension, which can cause permanent lung damage
How can patent ductus arteriosus lead to heart failure?
A patent ductus arteriosus can eventually cause the heart to enlarge and weaken
What is a patent ductus arteriosus treated with?
Prostaglandin inhibitors (e.g. ibuprofen)
What can atrial septal defects be caused by?
Failure of septum primum and secundum to fuse after birth
What can cause failure of septum primum and secundum to fuse?
Malformations in the septum primum or secundum (most common) such that they don’t overlap. Leaves gap so blood can flow between atria.
What is a patent foramen ovale?
Foramen ovale (small, flap-like opening present in wall between right and left atria) fails to close during infancy
How common is a patent foramen ovale?
1 in 4 people
Why is a patent foramen ovale usually asymptomatic?
Higher pressure in LA pushes septum primum against septum secundum and mechanically shuts valve
When can a patent foramen ovale cause problems?
If there is higher pressure in RA this can push the flimsy septum primum open and allow blood to shunt from right to left
What is the ostium/foramen secundum?
A foramen in the septum primum (not the same as the foramen ovale which is an opening in the septum secundum)
What is an ostium secundum defect? What is it caused by?
Caused by excessive apoptosis in septum primum causing abnormally large opening. Or by inadequate development of the septum secundum – such as when the foramen ovale and foramen secundum overlap.
What is result of ostium secundum defect?
Blood is shunted left to right - Can cause enlargement of right atrium and ventricle - Small defects are asymptomatic (<5mm)
What is a ‘common atrium’?
Complete absence of atrial septum
What is ‘common atrium’ caused by?
Failure of development of septum primum and secundum
What is result of premature closing of foramen ovale?
Results in hypertrophy of the right side of the heart and underdevelopment of the left side - No blood passing into left side so it doesn’t develop - Death usually occurs shortly after birth
When does premature closing of foramen ovale occur?
During prenatal life
What is the most common congenital defect?
Ventricular septal defect
What do ventricular septal defects often affect?
Can affect the muscular or membranous part of the interventricular septum (Muscular defects often resolve themselves as child grows)
What do ventricular septal defects result in?
Shunting of blood from left to right –> resulting in pulmonary hypertension and hypertrophy of right ventricle
What do the conotruncal swellings that form the conotruncal septum rely on?
The migration of neural crest cells from the neural tube
What can lead to defects in septation of truncus arteriosus into pulmonary trunk and aorta?
Abnormal crest cell development/migration
What is result of truncus arteriosus?
- Oxygen-poor blood and oxygen-rich blood are mixed together as blood flows to the lungs and the rest of the body - Too much blood goes to the lungs and the heart works harder to pump blood to the rest of the body
In truncus arteriosus, what valve is present?
Instead of having both an aortic valve and a pulmonary valve, babies with truncus arteriosus have a single common valve (truncal valve)
What is persistent truncus arteriosus?
Conotruncal septum completely absent so cannot fuse with inter ventricular septum (ventricular septal defects)
What is result of persistent truncus arteriosus?
Undivided truncus is in communication with both ventricles and receives oxygenated and deoxygenated blood Must be surgically corrected or causes heart failure
What is the transposition of great vessels?
Conotruncal septum runs straight down instead of forming in a spiral. Aorta arises from right ventricle and pulmonary artery arises from left ventricle.
What needs to exist to survive with the transposition of great vessels?
An accompanying shunt such as a VSD, patent foramen ovale or patent ductus arteriosus
What is ‘Tetralogy of Fallot’?
Collection of 4 abnormalities caused by the same primary defect. 1. Pulmonary stenosis 2. Ventricular septal defect 3. Overriding aorta 4. Right ventricular hypertrophy (caused by higher pressure on right side) All cause poor oxygenation of body (cyanosis)
What is Tetralogy of Fallot’ caused by?
Unequal division of the truncus arteriosus caused by anterior displacement of the aorticopulmonary septum.
What is coarction of the aorta?
Narrowing of the aorta that occurs near the ductus arteriosus
What are the 2 classifications of coarction?
- Preductal 2. Post ductal
What is preductal coarction of aorta?
During development, the ductus arteriosus compensates for narrowing –> ductus arteriosus usually remains patent after birth
What can obliteration of the ductus arteriosus in infants result in? What is it treated by?
Rapid decline of infant with hypo perfusion of lower body. Treated by administering prostaglandins to keep ductus arteriosus open
What is differential cyanosis?
Upper body and head well perfused, lower body cyanotic
What is post ductal coarction of aorta?
More common During development a collateral circulation is established to bypass the narrowing
What is this collateral circulation in post ductal coarction?
Blood passes through the subclavian arteries to the internal thoracic arteries to intercostal arteries to the descending aorta
What is result of post ductal coarction and this collateral circulation?
Internal thoracic and intercostal arteries enlarge to carry greater blood flow
