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Cardiovascular system > Lecture 8- Aetiology of congenital heart disease > Flashcards

Lecture 8- Aetiology of congenital heart disease Flashcards

1
Q

pathophysiology basics

A
  1. Right ventricle pumps deoxygenated bloods to lungs
  2. Pulmonary circulation has low resistance
  3. Left ventricle pumps oxygenated blood at systemic blood pressure to aorta
  4. Each ventricle is morphologically adapted for its task
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2
Q
  1. Right ventricle pumps deoxygenated bloods to lungs
A
  • pO2 is 67%
  • Venous pressure in atrium 4mmHg
  • Pressure 25/4 mmHg in the ventricle
  • Blood moves from the atria to ventricle due to ventricle diastole and atria systole (contraction)
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3
Q
  1. Pulmonary circulation has low resistance
A
  • pressure is 25/10mmg in pulmonary trunk
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4
Q
  1. Left ventricle pumps oxygenated blood at systemic blood pressure to aorta
A
  • pO2 is 99-100%
  • left atria- slightly higher pressure than in right atria- 8-10mmHg
  • Left ventricle – 120/10 mmHg
  • 120 is the pressure needed to pump around the whole body
  • aorta pressure- 120/80mmHg
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5
Q
  1. Each ventricle is morphologically adapted for its task
A

Left ventricle has much more muscle

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6
Q

pressure in right atria

A

0-4 mmHg

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7
Q

pressure in right ventricle

A
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8
Q

pressure in pulmonary artery

A

25/10

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9
Q

pressure in left atrium

A

8-10 mmHg

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10
Q

pressure in left ventricle

A

120/10 mmHg

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11
Q

pressure in aorta

A

120/80

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12
Q

there is ……. between either sides of the heart

A

no mixing

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13
Q

How is blood pumped back to the heart?

A
  • Residual pressure
  • Muscle movement
  • Valves
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14
Q

Aetiology of congenital HD

A
  • Genetic
    • Downs, Turners, Marfan’s
    • Polygenic
  • Environmental
    • Teratogenicity from drugs, alcohol etc
  • Maternal infections
    • Rubella, toxoplasmosis
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15
Q

Shunts

A
  • Atrial
  • Ventricular
  • Atrioventricular
  • Aorto-pulmonary (ductal)
    • Present in foetal life- should close after birth
    • Bypass channel from the lungs
    • Resistant in the lungs would be too high and damage lungs
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16
Q
A
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17
Q

Ductus venosus

A

- by-pass the liver (highly metabolic)

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18
Q

Foramen ovale-

A

by-pass the right ventricle and lungs

19
Q

Ductus arteriosus

A

- by-pass the lungs

20
Q

classification of congenital heart disease

A

acyanotic, cyanotic, respiratory cyanosis

21
Q

Acyanotic (not blue blood)- red

A
  • Left to right shunt (ASD, VSD, PDA)
  • Obstructive lesions: aortic stenosis (hypoplasia)
  • Pulmonary stenosis (valve, outflow branch)
  • Coarctation of the aorta (narrowing) and mitral stenosis
22
Q

Cyanotic

*

A
  • blue
  • Circulating systemic oxygen levels are lower (complex, right to left shunts)
    • Tetralogy of fallow (VSD/pulm stenosis)
    • Transposition of the great arteries
    • Total anomalous pulmonary venous drainage
    • Univentricular heart
23
Q

Respiratory cyanosis

A
  • Asphyxiation
  • Pneumonia ​
24
Q

Central vs peripheral cynosis

A

Central cyanosis occurs when the partial pressure of oxygen (pO2) in the systemic circulation is low.

–> Babies have a blue discolouration to their face, mouth and tongue.

Peripheral cyanosis is blue discolouration of the peripheries due to reduced perfusion, e.g. in cold weather, arteries to the fingers and toes constrict

25
Q

acyantoic defects

A
  • Left to right shunts
    • Atrial septal defects (ASD)
    • Ventricular septal defect (VSD)
    • Patient ductus arteriosus (PDA)
  • Obstructive lesions
    • Aortic stenosis (hypoplasia)
    • Pulmonary stenosis (valve, outflow, branch)
    • Mitral stenosis
    • Coarctation of the aorta
26
Q

outline the aetiology of Atrial septal defect (ASD)

A
  • Caused by underdevelopment of the septum primum or secundum, resulting in a hole in the atrial septum
    • Allows blood in the left atrium to flow into the right atrium
  • Increased volume in the right atrium leads to a higher volume of blood being pumped around the pulmonary circulation
    • If left untreated, this will cause damage to the vasculature and fibrosis of the arteries in the lungs
    • Making arteries less distensible which increases resistance to blood flow and results in pulmonary hypertension:
      • Meaning right side of the heart must work against the increased AFTERLOAD
      • Can cause right heart enlargement (hypertrophy)à leading to heart failure
      • Can also cause pulmonary oedema as blood under high pressure forces fluid out of the capillaries into the lungs
27
Q

patent foramen ovale (PFO)

A

is not classed as an ASD. PFO is caused by the failure of the foramen ovale to shut after birth. It is not an ASD because it is a unidirectional shunt (right atrium to left atrium) and there is no defect in the septum of the atria. In adults it generally doesn’t cause symptoms. This is because the pressure in the left ventricle is higher than that in the right, so the shunt does not allow blood to move down this gradient.

28
Q

Serious ASD

A
  • If pressure in the pulmonary circulation becomes high enough due to increased resistance, the pressure in the right atrium will exceed that in the left
  • This will cause the flow of blood to reverse and deoxygenated blood will mix with oxygenated blood in the left atrium
    • Patient will become cyanotic due to reduce pO2 in systemic circulation- Eisenmenger syndrome
29
Q

Ventricular septal defect (VSD)

A
  • During development of the interventricular septum, the membranous portion of the septum fails to develop properly
    • Primary interventricular foramen remains open
  • Blood in the left ventricle will flow into the right ventricle
  • The pressure difference between the ventricles is greater than that between he atria, so more blood movement in VSD than ASD
  • By the same mechanism as ASD, VSD if left untreated will cause pulmonary hypertension, right sided hypertrophy –>heart failure
30
Q

Atrioventricular septal defect

A
  • Caused by failure of the endocardial cushions to develop properly
  • Results in a hole in the middle of the heart with one common atrioventricular valve, instead of a mitral and pulmonary valve
  • Common in Down’s syndrome
31
Q

Patent ductus arteriosus (PDA)

A
  • Ductus arteriosus connecting the right pulmonary artery to the arch of the aorta normally shunts after the baby takes its first breath, however in PDA it remains open
  • This patient connection allows blood under high pressure in the aorta to flow into the pulmonary artery
  • This result in a higher volume of blood in the pulmonary artery, leading to a high AFTERLOAD for the right ventricle, which can eventually causes right-sided heart failure)
  • This is acyanotic heart defect because the blood reaching the systemic circulation is fully saturated with oxygen from, the lungs
32
Q

Aortic/pulmonary stenosis

A
  • One or both semilunar valves don’t develop properly and are narrow when the baby is born
  • e.g. in the aortic valve – only has 2 leaflets
    • Results in left/right ventricular hypertrophy as the heart is having to generate more force to push blood through the stenosed valve
      • Hypertrophy can lead to heart failure
33
Q

Coarctation of the aorta

A
  • Congenital narrowing of part of the aorta- commonly around the ductus arteriosus area
  • Upstream of the coarctation (towards the heart), blood pressure is high because it struggles to flow past the coarctation

Increases risk of aneurysms of the aortic arch, and aortic root dilation which can lead to aortic valve regurgitation

34
Q

signs of coarctation of the aorta

A
  • Downstream of the coarctation (towards the body), patients will have weak pulses and claudication (cramping in the legs due to reduced perfusion)
    • If narrowing is after the 3 branches of the arch of the aorta, there will be a delay between feeling the radial and femoral pulses (radio-femoral delay)
    • If narrowing is between the brachiocephalic trunk and the left subclavian, then there will be a delay between feeling the radial pulses in both wrists- radial-radial delay
35
Q

presentation of of coarctation of the aorta

A
36
Q

Cyanotic defects

A

A group of heart defects that present with central cyanosis- blood in the systemic circulation is not saturated with oxygen so pO2 is low.

  1. Tetralogy of Fallot
  2. Transposition of the great arteries
  3. Total anomalous pulmonary venous drainage
  4. Univentricular heart
37
Q

Tricuspid atresia

A
  • The tricuspid valve fails to form
  • Blood cannot flow from the right atrium to the right ventricle
  • In these babies, there is ASD and VSD which allows blood to flow into the pulmonary circulation
  • Deoxygenated blood mixes with oxygenated blood in the left side of the heart as it can only move through the ASD as the valve is fused
  • This mixing means that blood being pumped into the aorta and to the body will have a low pO2 resulting in central cyanosis
38
Q
A
39
Q

Pulmonary atresia

A
  • The pulmonary valve fails to form
  • The only way the blood can leave the right hand side of the heart is via a septal defect
  • A ventricular septal effect allows deoxygenated blood to move from the right ventricle to the left ventricle where it mixes with oxygenated blood
  • Newborns can have a patent ductus arteriosus to allow blood into pulmonary circulation
40
Q

Transposition of the great arteries

A
  • The aorticopulmonary septum forms, but does not spiral, therefore when the baby is born the aorta arises from the right ventricle, and the pulmonary trunk arises from the left ventricle
  • The pulmonary and systemic circulation are almost separates, with only an ASD and PDA allowing some oxygenated blood to enter the systemic circulation
  • This is a neonatal emergency and prostaglandins must be given to the baby quickly in order to maintain the PDA and allow some oxygenated blood into the systemic circulation until surgery can be performed
41
Q

Tetralogy of fallot

A

Characterised by 4 defects that present together:

  1. Pulmonary stenosis- the pulmonary artery or valve is narrowed, so less blood can enter
  2. Overriding aorta- aorta is large and situated right next to the VSD so most of the blood in the heart flows through it
  3. Ventricular septal defect- allows blood from the right ventricle which cannot be pumped through the stenosed pulmonary artery/valve to move into the left ventricle and be pumped around the body via the aorta
  4. Hypertrophy of the right ventricle- in an attempt to generate more force to pump blood through the stenosis in the pulmonary artery
42
Q

Univentricular heart

A
  • The ventricular septum doesn’t form, so oxygenated and deoxygenated blood mixes in the ventricle, and gets pumped into both the aorta and pulmonary trunk
43
Q

Hypoplastic left heart

A
  • Mitral or aortic valve are stenosed in utero which means that less blood flows into the left ventricle- results in left ventricle being underdeveloped
  • ASD allows blood to flow into the right side of the heart and be pumped to the pulmonary artery and a PDA allows this blood to enter the aorta from the left pulmonary artery

Cardiovascular system (30 decks)

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