CVT 100 #8 Physics PP Pathology

Question 1

The usual complication of atherosclerotic obstruction of coronary arteries:

Answer 1

myocardial infarction(heart attack)

Question 2

Infarct:

Answer 2

tissue death due to ischemia

Question 3

The usual complication of plaque in carotid arteries:

Answer 3

CVA (stroke)—cerebrovascular infarctiondue to flow restriction and/orembolic activity(brain infarction)

Question 4

1 killer in the U.S is

Answer 4

M.I. is the #1 killer in the U.S

Question 5

3 killer in the U.S. is

Answer 5

Stroke is the #3 killer.

Question 6

Another complication:Aneurysm

Answer 6

Weakening and bulging of the cardiac or arterial wall.

Can be due to infarcted tissue, atherosclerotic degeneration, infection, or congenital weakness.

Question 7

Aneurysm results when

Answer 7

the wall can no longer provide the tensile strength—the tension— to withstand pressure.

Question 8

Law of LaPlace:

Answer 8

variables that influence wall tension
T oc P x d
Wall tension oc pressure x diameter

Question 9

The larger the diameter,

Answer 9

the more tension is required to sustain a given pressure.

Cancel units
dynes x cm —> dynes
——— ——-
cm^2 cm

Question 10

In the vascular system:
Aorta ____cm
Pressure:____mmHg
Wall tension: _______ dynes/cm

Answer 10

Aorta (2 cm)
Pressure: 100 mmHg
Wall tension: 170,000 dynes/cm

Question 11

In the vascular system:
Capillary ____ cm
Pressure: ___ mmHg
Wall tension: ____ dynes/cm

Answer 11

Capillary (.0008 cm)
Pressure: 30 mmHg
Wall tension: 16 dynes/cm

Question 12

Pressure in aorta:_______ times that of capillary

Answer 12

3 or 4 times

Question 13

Diameter of aorta:_______ times that of capillary

Answer 13

2500 times

Question 14

Wall tension of aorta:________ times that of capillary

Answer 14

10,000 times

Question 15

In the body, the mean pressure doesn’t change much—it’s the diameter that changes as the wall weakens, requiring more…

Answer 15

wall tensionto hold things together.(Of course, a hypertensive episode could trigger aneurysm rupture as well…)

Question 16

T = P * r
100 = 50 x 2
Double the radius:
200 = 50 x 4
Twice as much wall tension needed

Answer 16

Twice as much wall tension needed

Question 17

Vicious circle:More radius —> more weaknessMore weakness —>

Answer 17

more bulging —> more weakness…etc.(Besides, the more complete form of LaPlace’s equation includes wall thickness, which is reduced with aneurysmal changes.Worse yet.)

Question 18

Venous side of the circulation has two basic functions:

Answer 18

1. Return blood to heart
2. Act as reservoir of blood

2/3 to 3/4 of body’s blood is in the venous reservoir at rest

Question 19

Two functions of the venous reservoir:

Answer 19

1. Provide increased flow during exercise

2. Provide volume to the core circulation in the event of severe hemorrhage

Question 20

Two venous pools:

Answer 20

1. Peripheral venous pool

2. Central venous pool(thoracic veins, vena cavae, and RA)

Question 21

Compliance:

Compliance = ∆ volume
—————-
∆ internal pressure

Answer 21

Ability to expand and contain more volumewith little pressure increase.

Question 22

Veins are compliant because

Answer 22

of normally semi-collapsed state, not because of elasticity.

Question 23

Veins can hold much more volume before

Answer 23

pressure increases significantly

Volume up 250% with only0 – 15 mmHg increase in pressure

Question 24

Veins:

Answer 24

Thin-walled

Less elastin and smooth muscle in the media compared to arteries

Easily collapsed by extrinsic pressure

Question 25

Work muscles:

Answer 25

Collapse veins, sending bloodback to heart

This increases C.O., sending more nutrients to working muscles

Question 26

Venous return:

Answer 26

Only about 15 mmHg pressure gradient to move blood back.

Need other sources of energy to get blood back to RA.

Question 27

Also, must overcome HYDROSTATIC PRESSURE(fluid not moving):

Answer 27

gravity pulling on column of fluid

Potentially about 90 mmHg in standing person

Question 28

Five mechanisms to aid venous return:

Answer 28

1. Venous valve
2. Skeletal muscle pump
   3. Respiratory pump
3. Cardiac suction effect
4. Vasomotor tone

Question 29

One-way valves ensure that

Answer 29

blood can move only to heart

Closed by pressure gradient to prevent backflow

Presence of valves breaks upcolumn of fluid

Question 30

Valves are sparse in femoral/popliteal veins,numerous in calf veins—why?

Answer 30

a

Question 31

Muscle pump:“Peripheral heart”

Answer 31

Contraction squeezes veins, sending blood toward heart

Relaxation “pulls” blood from muscular veins and superficial veins

Question 32

Respiratory pump

Inspiration:

Expiration:

Answer 32

Inspiration: lower pressure in thoracic cavity,higher pressure in abdominal cavity

Expiration: higher pressure in thoracic cavity,lower pressure in abdomen

Question 33

Low intrathoracic pressure on inspiration increases flow from

Answer 33

brachiocephalic and abdominal veins

Question 34

Lower intra-abdominal pressure on expiration allows flow from

Answer 34

lower extremities to resume

Question 35

Valsalva maneuver:

Answer 35

Big breath in,hold breath,bear down.

Increases pressure in both thoracic and abdominal cavities, so venous return is slowed or stopped everywhere.

Question 36

Cardiac suction effect:

Answer 36

Atrioventricular ring pulls down during systole, lowering intra-atrial pressure and encouraging inflow from venae cavae and pulmonary veins

Question 37

Vasomotor tone:

Answer 37

Physical or emotional stress causes sympathetic nerve changes that cause tensing of venous walls, promoting flow toward heart.

Question 38

Lower-extremity venous anatomy:

Answer 38

Deep veins (femoral, popliteal, calf)

Superficial veins (greater and lesser saphenous, tributaries)

Perforating veins

Question 39

LE deep veins:

out of order

Answer 39

Common femoral
Superficial femoral
Deep femoral (profunda femoris)Popliteal
Tibioperoneal trunk
Anterior tibial
Posterior tibial
Peroneal

Question 40

LE superficial veins:

Answer 40

Great saphenous
Small saphenous

These communicate with deep veins via PERFORATING VEINS, which allow flow only from superficial to deep (see muscle pump)

Question 41

Venous diseaseAcute vs. chronic

Answer 41

Deep vein thrombosis—important because it can lead to pulmonary embolus(PE)

Question 42

Virchow’s triad:

Answer 42

1. Stasis
2. Hypercoagulability
3. Vessel wall injury

Question 43

Stasis:

Answer 43

Blood not moving tends to clot(higher concentration of platelets)

Question 44

Hypercoagulability:

Answer 44

Some conditions make the blood more likely to clot.(Blood is in continual balance ofclotting vs. not clotting)

Question 45

Vessel wall injury:

Answer 45

Intima is smooth, tends to repel platelets.Interruption of intimal surface causes platelets to aggregate, which can lead to thrombosis.

Question 46

DVT is thought to originate often in two places:

Answer 46

1. Muscular veins in calf (stasis)

2. Behind valve leaflets(stasis)

Question 47

Once thrombus gets started, it tends to Typical DVT fills major veinsall the way up to femoral or even iliac veins.

Answer 47

propagate—grow to fill vein lumen,extend along the vein.

Question 48

Typical DVT fills

Answer 48

major veinsall the way up to femoral or even iliac veins.

Question 49

Fresh thrombus is more

Answer 49

fragile, poorly adherent to vein wall, more likely to break off and embolize to pulmonary arteries.

Question 50

DVT symptoms:

Answer 50

SwellingPainAchingWarmth of limbSometimes no symptoms…

Question 51

Single condition causingchronic venous symptoms:venous hypertensiondue to

Answer 51

1. Venous valvular insufficiencyand/or

2. Chronic venous obstruction

Question 52

Diagnosis of DVT

Answer 52

Now we do venous imagingwith ultrasound

Old way: venous outflow plethysmography(along with CW venous Doppler)

Question 53

Venous imaging:

Answer 53

Scan in short axis.
Push with probe every 2-3 cm to make walls meet (coapt).
This demonstrates absence of thrombus.
SFA and SFV

Question 54

Acute thrombus:

Answer 54

Dark intraluminal echoes
Homogeneous echoes
Distension of vein
Poor wall attachment (“tail”)

Question 55

Chronic thrombus:

Answer 55

Bright intraluminal echoes
Heterogeneous echoes
Possibly retracted, small lumen
Well attached to wall
May see recanalization, collaterals
Vein may be invisible

Question 56

Doppler is also part of the venous duplex exam—assess for

Answer 56

normal or abnormal venous flow character.

Question 57

Doppler is also used to evaluate for

Answer 57

valvular insufficiency:

Try to provoke backflow (reflux)with proximal and distal compression maneuvers.

Question 58

Plethysmography: recording oflimb volume changes
Three types:
1. Pneumoplethysmography
2. Strain gauge 
3. Impedance plethysmography

Answer 58

With all three types:Inflate thigh cuff to 50 mmHg to pool blood in the calf veins.Monitor calf blood volume for increase,then for rapid decrease when thigh cuff is deflated.(Capacitance/outflow)

1. Pneumo (air cuff):Calf cuff connected to pressure transducerResponds to increase of calf circumference due to pooling of blood
2. Strain gauge:Elastic tube with mercury(conductive fluid)Calf circumference increase stretches the strain gauge and increases electrical resistance.
3. Impedance:Two electrode bands on calfTiny current runs between the electrodesBlood is a good conductor,so more blood means less impedance(electrical resistance)