Hemodynamics, Cardiac Cycle and Heart Sounds

Question 1

what is flow? what are the factors that affect it?

pressure changes
resistance
radius
viscosity
length

Answer 1

Flow: the AMOUNT (quanitity) of blood that is passing through a specific spot at a given area of time

FLOW = change P/ R

where the change in pressure (bigger change) will increase flow
where more resistnace will decrease flow

as blood flows through a rigid tube– energy is lost to the interactions with the walls & pressure will decrease

longer length to travel: less flow
more viscous: less flow
bigger tube (radius): more flow

Question 2

what is viscosity? how does it play into blood and flow?

Answer 2

viscosity: thickness or slippyness of the fluid
think honey v water
flow is inversely related to viscosity – more viscous = less flow

BLOOD
suspended cells: hematocrit (45%) of the blood
plasma: the blood without cells (water and salts)clotting factors
serum: essentail the fluid left

increase hematocrit = increase viscosity & decrease flow
decrease veloscity of flow = increase viscosity & decrease flow
decrease temperature pf blood = increase viscosity

• comes into play with small and large vessels

Question 3

Laminar v Turbulment Blood Flow

factors that determine

Answer 3

Laminar: streamlined flow that is efficent (think the middle)

Turbulent: wacky mixing and flowing thats unefficient (outside)
- this occurs becuase increased interactions with the walls therefore increased resistance in the vessel
-* happens in atherosclerosis*

high velocity: laminar flow, stagnent flow = turbulent

Factors
- diameter (bigger = more room to hit the walls) = turbulent
- density: more dense = more tubulent
- more viscous: less turbulent

turbulence creates sound — why we hear murmurs fast (velocity = turbulence)
anemia = murmue with increase turbulence

Question 4

difference between velocity and flow

Answer 4

velocity = a SPEED
flow = an amount
Flow = v X area

big area — less fast flow
small area – faster flow

think thumb over garden hose

Question 5

explain the relationship between pressure, velocity, flow and kinetic energy of blood

how does aortic stenous affect this

Answer 5

total energy will remain constant

the kinetic energy (velocity) can be converted into potential energy (pressure) so that total energy is not completely lost

the speed will increase through the small vessel therefore decreasing the pressure on teh wall (since the KE and PE have to balance each other) if you icnrease KE the PE (pressure) will decrease)

aortic stenosis: the aortic valve narrows: faster speed (velocity) of the blood to flow through a smaller tube –> decreases the pressure and less force on the walls
less pressure –> less flow to the cornary arteries

Question 6

how does PE and KE play into the driving forces for blood flow

-gravity?

Answer 6

since the KE for the blood is small (its the same “speed” velocity – the changes are in the pressures (PE)

PE pressures are the DRIVING forced of blood flow through the body

flow determiend by the CHANGE in pressures

gravity (downward) will increase pressure (higher p in legs)

Question 7

describe (in headings) the phases of the cardiac cycle based on the pressures and what is going on

Answer 7

1. systole occurs - the point at which the blood is pumped by the heart (1/3 of total time)
   —> isovolumetric contraction : the mitral valve closes due to increased pressure in the ventricle over the atrium, but the pressure is not great enough for the aortic valve to open
   –> ejection phase of contraction : the blood is forced out
   ——— initally its a FAST force through the aortic valve = Rapid Ejection Phase
   —— then its a bit slower getting the last drops out = reduced ejection phase
2. Diastole occurs - the blood has been pumped out & now the relaxation of the heart occurs
   —> isovolumetric relation: aortic valve closts becuase the pressure is now higher in the aorta than the ventricle, but the mitral valve has not reopened yet
   —> Passive Filling Phase: the blood beging to fill in the ventricle from the atrium due to the “baseline” pressure differences from the atrium to the ventricle
   ——Rapid FIlling Phase: the mitral valve opens & blood begins to flow in due to the change in pressures now
   —– Reduced FIlling Phase: the rest of the blood flows in
   –> Atrial Systole: the atria contract and push the blood into the ventricle

atrial systole occurs during diastole!!

Question 8

what are the heart sounds?
S1, S2, S3, S4

Answer 8

S1: the AV valves (tricuspid and mitral) closing (after the blood has rushed into the ventricles) –early systole

S2: the pulmonary and aortic valves closing, after blood has rushed from the ventricles into these arteries and the high pressure forces these to close — late systole/early diastole

S3: mostly an abnormal heart sound – in early diastole when the blood is passively going from the atria to the ventricle – the sound of hte blood flowing into the ventricle — heard because of increased compliance of the ventricle — so complinat it opens way big and “hits” chest wall
- can be normal in kids, athletes
- but can be a sign of heart failure becuase the left ventrcile is so big

S4: late diastole –> when the ATRIA CONTRACT you hear the S4 because the ventricle is stiff –> so when the atria contract to push the last bits of blood in– the stiff wall creates turbulent flow heard right before S1

Question 9

when will you hear murmurs (patho. states)

Answer 9

• 1. flow across an obstruction (aortic stenosis)
• 2. increased flow across normal structures – more flow when less viscous (anemia) will flow faster –> more turbulence
• 3. flow into a dilated strcture (anyeurseum)
• 4. backwards flow with bad valve (aortic regurg)
• 5. shunting (AS defect in congential from high to low p)