Lec 26 Congenital Heart DIsease Flow Dynamics Flashcards

1
Q

What determines the driving force for systemic flow? what about the pulmonary circulation?

A

systemic = pressure difference between aorta and central venous pressure pushing blood through the heart

pulmonary = pressure difference between pulm artery and LA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is Ohm’s law for flow?

A

delta P = Q * R

pressure drop = mean flow * mean resistance

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Why do we measure average rather than instantaneous flow?

A
  • easier to conceptualize and measure

limitation: instantaneous behavior of circulation can be obfuscated by these models

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the equation for systemic resistance?

A

Rs = (Pao - Pra) / CI

[R = delta P/flow]

Rs = systemic resistance
Pao = aortic P
Pra = right atrium P
CI = cardiac index
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is cardiac index?

A

CI = cardiac output indexed to body surface area

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What happens to PVR after birth?

A

starts out really high and declines to adult level

means there is a rapid decline in pulm/systemic resistance ratio

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is normal mature level of PVR [pulm ascular resistance]?

A

2 woods units

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What 3 factors alter resistance to blood flow?

A
  1. blood viscosity
  2. . vessel length
  3. vessel radius [most important]
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What determines blood viscosity?

A
  • high hematocrit [Hct] and protein conc –> high viscosity –> increase resistance
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is poiseulle’s equation?

A

R = 8 * Ln/pi*r^4

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is relationship relative flow through parallel outlets from single reservoir?

A

relative flow rate proportional to relative resistances

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What happens to resistance when resistors are added in parallel?

A

resistance lowered!

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What do we assume if non-restrictive “large” VSD when we are calculations flows/pressures?

A
  • systolic RV and LV pressures equalize thus aortic and pulmonary artery pressure equal in systole
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

How do you determine Qp/Qs the pulmonary to systemic flow ratio?

A

Qp/Qs is inversely proportional to resistance ratio Rp/Rs

–> the ratio of resistances determines the amount of shunting through VSD

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How to model smaller/restrictive VSD?

A

from point of view of LV: “pulmonary resistance” part of the equation = combo of VSD resistance and pulm vascular resistance in series

–> increased resistance of small VSD affects Qp/Qs ratio by lowering pulm artery:aortic P ratio

How well did you know this?
1
Not at all
2
3
4
5
Perfectly