Development of the heart 2 Flashcards
What is dextrocardia?
Dextrocardia is a rare heart condition in which your heart points toward the right side of your chest instead of the left side.
What is dextrocardia a result of?
• Dextrocardia may be a result of abnormal cardiac looping or may be induced during gastrulation (week 3) when laterality (left and right sides) is determined
What is isolated dextrocardia?
• Isolated dextrocardia is associated with other structural defects including abnormal connections with veins and arteries or abnormal septation of the heart
What normally happens to the ductus arteriosus shortly after birth?
The ductus arteriosus closes soon after birth due to increasing oxygen tension and a decrease in circulating prostaglandins.
What does a patent ductus arteriosus allow?
A patent ductus arteriosus after birth allows shunting of blood from the aorta to the pulmonary artery.
Oxygenated blood travels back to the lungs then returns to the heart to be pumped out again – increases workload of the heart
What does patent ductus arteriosus lead to in terms of conditions?
Can lead to pulmonary hypertension, ventricular hypertrophy and heart failure.
How is patent ductus arteriosus treated?
Normally- Ductus arteriosum has contractile cells begin to contract so opening gets smaller. In response to decreasing prostaglandins causes contractile cells to contact.
Patent ductus arteriosus doesn’t have a decrease in prostaglandins.
- Treated with prostaglandin inhibitors- help decrease prostaglandins so closes ductus arteriosus
- Patent ductus arteriosus may be an isolated defect or occur with other cardiac defects
- Note – in some cardiac defects a patent ductus arteriosus is essential to life
How do atrial septal defects occur?
secundum to fuse after birth – probe patent foramen ovale
Can be due to malformations in the septum primum or secundum such that they do not overlap and therefore leave a gap (most commonly due defects in septum secundum)
What is probe patent foramen ovale?
A “probe patent” foramen ovale is defined as a defect in the fossa ovalis that would be revealed with instrument probing.
How does the body react to have a probe patent foramen ovale?
- Usually asymptomatic, higher pressure in LA pushes septum primum against septum secundum and mechanically shuts valve
- However, if there is higher pressure in RA e.g. pulmonary hypertension this can push flimsy septum primum open and allow blood to shunt from right to left
What is a ostium secundum defect caused by?
- Can be caused by excessive apoptosis in septum primum or by inadequate development of the septum secundum such as the foramen ovale and foramen (ostium) secundum overlap
- Blood is shunted left to right – can cause enlargement of right atrium and ventricle
- Small defects (<5mm) may be asymptomatic, however, larger defects may require surgical repair
What is a common atrium defect? (cor triloculare biventriculare)
Cor= heart Triloculure= three chambers Biventricular= 2 ventricles
- Rare cardiac defect with complete absence of atrial septum
- Failure of development of the septum primum and septum secundum
- Reports of people undiagnosed until 20-30 years of life
What does premature closure of the foramen ovale result in?
- Closure of foramen ovale during prenatal life
- Results in hypertrophy of the right side of the heart and underdevelopment of the left side
- Death usually occurs shortly after birth
What are ventricular septal defects?
- Defects can affect the muscular or membranous part of the interventricular septum
- Defects affecting the muscular part of the interventricular septum often resolve themselves as the child grows- during development heart muscle grows and is repaired naturally. Heart muscle develops and covers ventricular septal defect
- Ventricular septal defects allow left to right shunting of blood – LHS greater pressure so shunts blood to RHS
- Can result in pulmonary hypertension and hypertrophy of right ventricle- when muscle of heart gets bigger
What is a trunks arteriosus?
Truncus arteriosus is a rare type of heart disease in which a single blood vessel (truncus arteriosus) comes out of the right and left ventricles, instead of the normal 2 vessels (pulmonary artery and aorta).
What is the Septation Defects of the Truncus Arteriosus?
- The conotruncal swellings that form the conotruncal septum rely in the migration of neural crest cells from the neural tube
- Abnormal neural crest cell development or migration can lead to a number of defects in septation of the truncus arteriosus into pulmonary trunk and aorta
- These include persistent truncus arteriosus (one common outflow tract), transposition of the great vessels (abnormal connections of chambers of heart) and Tetralogy of Fallot
What is persistent truncus arteriosus?
Conotruncal septum completely absent therefore cannot fuse with interventricular septum – ventricular septal defect
Undivided truncus is in communication with both ventricles – receives oxygenated and deoxygenated blood
What are symptoms of persistent truncus arteriosus?
- Symptoms include cyanosis (blue colour) at birth, lethargy, breathlessness, delayed growth
- Must be corrected surgically or will result in heart failure and death within 2 years
What is the transposition of the Great Vessels?
- Conotruncal septum does not form in a spiral but instead runs straight down
- Aorta arises from right ventricle and pulmonary artery from left ventricle
Are you able to live with transposition of the Great Vessels?
• Incompatible with life unless an accompanying shunt such as a VSD, patent foramen ovale or patent ductus arteriosus exists
What are the symptoms of transposition of the Great Vessels?
• Similar symptoms to persistent truncus arteriosus including cynaosis but can corrected surgically
How can we stay alive even if we have transposition of the Great Vessels?
Ductus arteriosus
What is the primary defect that causes Tetralogy of Fallot?
Unequal division of the truncus arteriosus caused by anterior displacement of the aorticopulmonary septum. Displacement of the septum produces four classic cardiac defects.
What are the four abnormalities of the Tetralogy of Fallot?
- pulmonary stenosis (narrowing)
- ventricular septal defect
- overriding aorta (rightward displacement of the aorta)
- right ventricular hypertrophy caused by higher pressure on the right side
What is coarctation of the aorta? What is the cause of this? How can it be classified?
- Narrowing of the aorta that occurs near the ductus arteriosus
- Cause is unknown but may be due to abnormal migration of cells from the ductus arteriosus
- Can be classifies as preductal or postductal in relation to ductus arteriosus
How can someone survive if they have preductal coarctation of the aorta?
- During development, the ductus arteriosus compensates for the narrowing
- After birth, the ductus arteriosus usually remains patent
What happens when someone that has preductal coarctation of the aorta but the ductus arteriosus is obliterated after birth? How can it be treated? What are the symptoms of this?
- Obliteration of the ductus arteriosus causes rapid decline of infant with hypoperfusion of the lower body
- Can be treated by administering prostaglandins to keep ductus arteriosus open
- Differential cyanosis – upper body and head well perfused, lower body cyanotic
How does post ductal coarctation of the aorta work?
- During development, a collateral circulation is established to bypass the narrowing
- Blood passes through the subclavian arteries to the internal thoracic arteries to intercostal arteries to the descending aorta
- Internal thoracic and intercostal arteries enlarge to carry greater blood flow
