congenital cardiac disease

Question 1

What are the remnants of the following embryological structures?
Ductus arteriosus?
Ductus venosus?
Umbillical arteries?
Umbillical veins?
Urachus?

Answer 1

ligamentum arteriosum
ligamentum venosum
medial umbillical liagemts
round ligament of the liver
medial umbillical ligaments

Question 2

Describe the fate of each of the embryological aortic arches:

Answer 2

The six embryological aortic arches form the great arteries of the neck and head:
- The third, fourth, and sixth aortic arches become adult vessels.
- The first two arches degenerate
- the fifth arch is rudimentary or absent.

Third aortic arch becomes the carotid arteries.
Left fourth aortic arch becomes the adult arch of the aorta.(The right fourth aortic arch becomes the right subclavian artery.)
The sixth aortic arch becomes a pulmonary artery.

Question 3

how does the atrial septae form

Answer 3

• Left and Right atria separated by septum primum - grows towards AV cushions
• O1 (gap connecting two atria) (opening 1) - Foramen primum - R to L blood flow
• Holes start to form in the septum primum and the second primum forms
• To maintain R to L flow - second septum develops - septum secundum
• Forms a second foramen - which occurs before closure of foramen primum - series of fenestrations

Question 4

What is the functional role of the foramen ovale in the fetus?

Answer 4

• Shunts oxygenated blood straight through RA to LA, doesn’t need to be sent to the lungs
• Pressure difference across FO keeps it open in fetus
• Patency maintained by high blood flow

Question 5

What types of atrial septal defects occur in animals? What are their impacts of oxygen delivery and cardiac function?

Answer 5

• PFO (persistent foramen ovale) common in people and cattle
• Other types of atrial septal defect (ASD), not usually clinically important

Question 6

What do the endocardial cushions form?

Answer 6

Within the atrio-ventricular (A-V) canal, left and right A-V endocardial cushions form chordae tendinae (thin strands of connective tissue that anchor the leaflets of each AV valve so that they cannot open into the atrium).

Question 7

What is the cardiac anomaly that results from endocardial cushion developmental failure?

Answer 7

Mitral/tricuspid dysplasia and ventral septum defects (VSD)

Question 8

What is Eisenmenger’s syndrome?

Answer 8

Reversal of shunt movement- incredibly rare. Left to right shunt (left pressure higher than right) remains as a result of atrial septal defect, ventricular septal defect or patent ductus arteriosus. More blood to pulmonary circulation than normal
- walls of pulmonary arteries become thicker walled and more muscular- pressure in right side increases- pulmonary hypertension, may exceed left side pressure- deoxygenated blood moves from right to left- deoxygenated blood into systemic system- lethargic animal.

Question 9

Identify the four defects of Tetralogy of Fallot
this condition results from what single error?

Answer 9

1. Pulmonic stenosis- pulmonary valve is too small, narrow or stiff
2. Large ventricular septal defect
3. Right ventricular hypertrophy- an increase and growth of muscle cells
4. Dextropositioning (overriding) of the aorta

This condition results from a single error: the cranial end of the bulbus cordis develops too far anteriorly giving rise to two unequally proportioned vessels- a large aorta and a smaller stenotic pulmonary trunk. The ventricular septal defect occurs because the septum is displaced too far anteriorly to contribute to the septum closure. Due to the shunting of blood from left to right, the pressure in the right ventricle is increased causing the walls of the right ventricle to expand- hypertrophy.

Question 10

Briefly consider the effects of the following on cardiac function (oxygenation and cardiac output)-Transposition of the great vessels

Answer 10

The aorta arises from the right ventricle and the pulmonary trunk from the left- deoxygenated blood is being transported around the body. Cardiac output will be reduced because the pulmonary trunk is not elastic enough to support high volume and high pressure blood.

Question 11

Briefly consider the effects of the following on cardiac function (oxygenation and cardiac output)-Aortic stenosis

Answer 11

Aortic valve is too small, narrow or stiff- oxygenation is unchanged
but cardiac output is reduced as less blood can leave the heart.

Question 12

Briefly consider the effects of the following on cardiac function (oxygenation and cardiac output)- Pulmonic stenosis

Answer 12

Pulmonary valve is too small, narrow or stiff- oxygenation is reduced as is cardiac output as less blood goes to the lungs.

Question 13

In what direction will blood flow across the following structures in an adult?
ventricular septal defect, patent ductus arteriosus, persistent foramen ovale

Answer 13

1. Ventricular septal defect, left ventricle to right ventricle
2. Patent ductus arteriosus, aorta into pulmonary artery
3. Persistent foramen ovale , right atrium to left atrium