Shunts and Obstructions: The Basic Principles - Feb 19

Question 1

Oxygen saturation in normal heart

Answer 1

Right side of heart 70%

Left side of heart (after pulmonary circulation) 98%

Question 2

Intra-cardiac shunts

Answer 2

1) Atrial septal defect
2) Ventrcular septal defect
3) Atrio-ventricular septal defect

Question 3

Extra-cardiac shunts

Answer 3

1) Patent ductus arteriosus

2) Aorto pulmonary window

Question 4

Types of atrial septal defects

Answer 4

1) Sinus venosus
2) Secundum
3) Primum
4) Coronary sinus

Question 5

Types of ventricular septal defect

Answer 5

1) Outlet
2) Muscular
3) Inlet
4) Membranous

Question 6

Patent ductus arteriosus

Answer 6

Shunt between pulmonary artery and aorta (to bypass the lungs as in fetus not oxygenated in lungs)

Question 7

Types of shunts based on flow direction

Answer 7

1) Left to right (acyanotic)
2) Right to left (cyanotic)
3) mixed (cyanotic)

Question 8

Shunts that cause left to right flow

Answer 8

1. Atrial septal defect
2. Ventricular septal defect
3. Atrio-ventricular septal defect
4. Patent ductus arteriosus

Question 9

Shunts that cause right to left flow

Answer 9

1. Eisenmenger syndrome

2. Tetralogy of fallot

Question 10

Shunts that cause mixed flow

Answer 10

1. Transposition of the great arteries

Question 11

What does degree/direction of shunting depend on

Answer 11

1. Pressure differences between chambers
2. Relative compliance between chambers
3. Size of defect

Question 12

Sequela of VSD left to right

Answer 12

Sequela = consequences of disease

1) Pulmonary over circulation
2) Pulmonary hypertension
3) Left sided chamber dilation
4) Left sided chamber dysfunction
5) Clinical heart failure
6) Arrhythmias

Question 13

Oxygen saturation changes with VSD

Answer 13

• RV and PA oxygenation increased

- rest the same

Question 14

Frank-Starlng curve

Answer 14

• As ventricular end-diastolic volume increases stroke volume increases
• sarcomere length is increasing with increasing end-diastolic volume up to optimal sarcomere length
• increases in end-diastolic volume passed this = LV dysfunction (overstretched)

Question 15

Sequela of PDA (left to right shunt)

Answer 15

1) Pulmonary over circulation
2) Pulmonary hypertension
3) Left sided chamber dilation
4) Left sided chamber dysfunction
5) Clinical heart failure
6) Arrhythmias

Question 16

Changes in oxygen saturation with PDA

Answer 16

-Increased oxygenation in PA

Question 17

Eisenmenger syndrome MOA

Answer 17

• ventricular septal defect with right to left shunting
• due to left to right shunting causing pulmonary over circulation
• leads to pulmonary hypertension
• pulmonary pressures exceed systemic pressure
• leads to right to left shunting

Question 18

When does right to left shunting occur

Answer 18

-due to severe right ventricular outflow tract obstruction

Question 19

Transposition of the great arteries

Answer 19

• aorta comes off the right ventricle
• pulmonary artery comes off the left ventricle
• results in 2 parallel circulations that require an anatomic connection to maintain mixing of pulmonary and systemic circulation (can be ventricular septal defect, atrial septal defect or patent ductus arteriosus)

Question 20

Changes in oxygen saturation with transposition of the great arteries

Answer 20

• SVC, RA, RV decreased O2 sat
• PA increased O2 sat
• LA/LV slightly decrease O2 sat
• Ao decreased O2 sat

Question 21

Anatomic obstruction locations

Answer 21

• obstruction to blood flow at the
  a) sub-valvular
  b) valvular
  c) supra-valvular

Question 22

Changes in O2 sat with anatomic obstruction

Answer 22

-O2 sat normal (no shunts)

Question 23

Physiologic implications of obstruction

Answer 23

• if severe = systemic hypoperfusion could result in increased oxygen extraction in the periphery –> results in low right sided oxygen saturation
• major issue = pressure gradients across the obstruction and the haemodynamic effect on the upstream chamber

Question 24

Aortic coarctation

Answer 24

-narrowing of aorta