4 - cardiac abnormalities

Question 1

at what stage does the heart develop?

Answer 1

heart development is during the foetal and neonatal stage, failure in transition can result in cardiac abnormality

Question 2

what causes ventricular septal defect (VSD)?

Answer 2

• the superior part of the ventricular septum fails to form causing blood to mix between ventricles
• more blood is shunted from the left to the right because the left ventricle is stronger

Question 3

what causes coarctation of the aorta?

Answer 3

• a part of the aorta is narrowed, increasing the workload of left ventricle
• occurs at birth
• can be pre or post ductal coaction
• it encourages collateral circulation

Question 4

what causes tetralogy of fallot?

Answer 4

multiple defects within the heart structure (4)

1. pulmonary trunk too narrow and pulmonary valve stenosed, resulting in
2. hypertrophied right ventricle
3. ventricular septal defect (hole between ventricles)
4. aorta opens from both ventricles (overriding aorta)

Question 5

circulation during the foetal stage?

Answer 5

• oxygen is supplied by placenta via the umbilical arteries
• lungs are fluid filled and there is a great resistance to blood flow
• oxygenated blood needs to enter the left side of the heart for systemic circulation
• the right side of the heart has higher pressure than the left

Question 6

circulation during the neonate stage?

Answer 6

• the various foetal openings and shunts need to be closed
• the left side of the heart has a higher pressure than the right
• failure to close or error in development may result in cardiac abnormality

Question 7

what are the developmental steps of the heart?

Answer 7

• heart develops from a single muscular tube at 22 days

- then develops into 4 chambers and needs to function as both foetal and neonatal heart

Question 8

what are the developmental steps of the atria?

Answer 8

1. the septum primum starts to grow and separates the single atrium into 2, blood flows through the ostium primum right to left
2. the septum primum joins to the endocardial cushion, the ostium secundum are made in septum primum to allow blood circulation
3. the septum secundum forms with foreman ovale to allow foetal circulation to continue

Question 9

what happens during the development of the ventricles?

Answer 9

• the single ventricle is divided into two by the growth of a septum
• if the septum fails to grow and join with the endocardial cushion or part of the septum is reabsorbed, then a hole will be present
• this hole is a ventricular septal defect (VSD)

Question 10

what is the difference between cyanotic and acyanotic abnormalities?

Answer 10

cyanotic - is when deoxygenated blood enters the systemic circulation

acyanotic - is when oxygenation of the systemic circulation is relatively normal (some oxygenated blood re-enter the pulmonary circulation)

Question 11

what are some examples of acyanotic abnormalities?

Answer 11

• ventricular septal defects (VSD’s)
• atrial septal defects (ASD’s)
• aortic stenosis
  coarctation of the aorta

Question 12

what are some examples of cyanotic abnormalities?

Answer 12

• tetralogy of fallot

- transpostiton of the great vessels

Question 13

what causes atrial septal defect (ASD)?

Answer 13

• the septum primum may be too short and unable to ver the foreman ovale
• the foreman ovale may be too large due to a failure of the septum secundum to grow down far enough

Question 14

what is Patent Ductus Arteriosus?

Answer 14

it is a condition where the ductus arteriosus fails to close after birth

• blood will flow from the higher pressure aorta to the lower pressure polmonary artery
• this will reduce blood flow via aorta and systemic circulation
• increasing blood flow to lungs causing polmonary oedema, resulting on right sided heart failure

Question 15

how does the formation of the aorta & pulmonary artery occur?

Answer 15

• the truncus arteriosus, needs to be divided into the aorta and pulmonary artery
• they must then line up with the correct ventricles
• the truncus ateriosus must spiral 180 degrees
• failure to spiral results in transposition of the great vessels
• failure to split equally results in a stenotic (narrowed) aorta or pulmonary artery

Question 16

what is transposition of the great vessels?

Answer 16

when the truncus ateriosus fails to spiral 180 degrees

• aorta arises from the right side and pulmonary artery from the left side of the heart
• survival requires some form of septal defect of patent ductus ateriosus
• surgery to “switch” vessels back

Question 17

what is unequal division of the truncus arterosus?

Answer 17

• is possible if the septum forms incorrectly, this may give a stenotic (narrow) aorta or pulmonary trunk

Question 18

what causes valve defects?

Answer 18

• can arise during development

- may not have an effect until later in life

Question 19

main function of the semilunar valves?

Answer 19

they prevent the aortic and pulmonary valves to change direction of their blood flow, causing ventricles to contract harder

Question 20

what is aortic valve stenosis?

Answer 20

• make it more difficult for blood to flow into aorta
• left ventricle responds by contracting harder
• causing increased pressure in LV
• resulting in hypertrophy due to increased contraction

Question 21

what is an aortic regurgitation murmur?

Answer 21

• during ventricular diastole, blood may flow back into ventricle
• blood flow through a leaky valve will cause a murmur

Question 22

what is mitral valve stenosis?

Answer 22

• it is a narrowing of the hearts mitral valve
• makes it more difficult for blood to flow to LV
• left atrium responds by contracting harder, increasing left atrial pressure LAP, resulting in hypertrophy of left atrium