Cardiac Cycle and Pressures

Question 1

Steps of Cardiac Cycle

Answer 1

1. Atrial Contraction
2. Isovolumetric contraction
3. Rapid ejection
4. Reduced ejection
5. Isovolumetric relaxation
6. rapid filling
7. Reduced filling

Question 2

S1

Answer 2

Closure of AV valves, beginning of systole

Question 3

S2

Answer 3

Passive closure of aortic, pulmonic valves

Question 4

S3

Answer 4

Rapid passive ventricular filling, ventricular gallop rhythm in LV heart failure

Can be normal finding in LA, may also be normal in some cats with gallop rhythm

Question 5

S4

Answer 5

atrial contraction vibrates stiff walls of ventricles during filling: atrial gallop rhythm indicative of cardiac dz

Question 6

RA Pressures

Answer 6

0-2

Question 7

RV Pressures

Answer 7

SAP 15-30, Diastolic 2-8

Question 8

PAP

Answer 8

15mm Hg MAP

Question 9

Pulmonary Capillaries

Answer 9

10mm Hg

Question 10

Pulmonary Venous pressure

Answer 10

8mm Hg

Question 11

LA P

Answer 11

2-5mm Hg

Question 12

LV pressures

Answer 12

100-140 SAP
DAP 3-12

Question 13

Aorta, large arteries

Answer 13

100mm Hg

Question 14

Arterioles

Answer 14

50mm Hg

Question 15

Capillaries

Answer 15

20mm Hg

Question 16

Vena Cava

Answer 16

4mm Hg

Question 17

Critical DO2

Answer 17

5-7mL/kg/min

Question 18

Critical HGB

Answer 18

4g/dL
Cyanosis at 5

Question 19

Critical O2ER

Answer 19

0.6(60%)

Question 20

CO - kidney

Answer 20

20-25%

Question 21

CO-liver

Answer 21

20-25%

Question 22

CO brain

Answer 22

10-15%

Question 23

CO heart (coronary BF)

Answer 23

5%

Question 24

CO - GIT

Answer 24

25%

Question 25

CO - skin

Answer 25

5%

Question 26

O2 ER: heart

Answer 26

10-12%

Question 27

O2 ER: SkM

Answer 27

2-5%

Question 28

O2ER kidney

Answer 28

2-3%

Question 29

O2ER:

Answer 29

GIT 4-6%

Question 30

Myocardial Oxygen Extraction

Answer 30

70-80% Why first thing to get upset with anemic patient or hypoxemic patients

Question 31

L anterior descending coronary artery + branches

Answer 31

largest mass in humans, swine, rats, non-human primates

Question 32

Circumflex coronary artery

Answer 32

largest mass in dogs, cats, horses, cattle  Dogs = extensive collateral circulation ***pigs, primates do not***

Question 33

Thebesian veins

Answer 33

present t/o heart, drain directly to cardiac chambers (4% venous return)

Question 34

What determines BF to myocardium

Answer 34

extravascular compression of intramural coronary vessels (30-40% of total resistance), contractile state of myocardium, HR Coronary blood flow determined by oxygen demand

Question 35

Cerebral Perfusion

Answer 35

autoregulation (50mL/100g/min) btw 60-150 mmHg CPP o Most important VD = CO2

Question 36

Bronchial Circulation

Answer 36

o Bronchial arteries  carry oxygenated blood to lungs  pulmonary capillaries (exchange occurs here)  bronchial veins (minimal)  pulmonary veins (majority)

Question 37

Pulmonary Circulation

Answer 37

Enter CO from RV: 10-15% blood vol (reservoir to stabilize LV ESV, systemic blood volume)  low-pressure system has limited ability to control regional distribution of BF --> pulm capillaries can collapse if significant decrease in BP

Question 38

HPV

Answer 38

 Alveolar hypoxia = most important stimulus for HPV  Site of action = extra-alveolar vessels Hypoxic conditions: pulm vessels constrict: increase pulmonary artery pressure --> distends, recruits under-perfused pulmonary vessels ==> shunting of blood to better ventilated alveoli = improvement in VQ ratio

Question 39

Splanchnic Circulation

Answer 39

o 25% CO, contains 20% blood vol o Splanchnic arteries = all arterial walls of preportal organs o Splanchnic veins = highly compliant, lrg vol reservoir, high population of a1/a2 R

Question 40

Spleen

Answer 40

Also has high population of a1/a2 receptors  Highly sensitive to adrenergic stimulation or blockade, spleen can hold significant reservoir of blood

Question 41

Role of Axs in Splanchnic Circulation

Answer 41

blunt/abolish ability of splanchnic circulation to mobilize blood

Question 42

How Splanchnic vasculature mobilizes volume

Answer 42

Volume mobilization = result of active VC, passive elastic recoil of splanchnic veins secondary to decrease arterial inflow Can compensate for up to 50-60% blood loss after moderate hemorrhage Active mobilization of splanchnic blood vessels = b2, a R activation --> act in concert to shift blood from splanchnic vasculature into systemic circulation via VC, decreased splanchnic vascular capacitance, decreased intrahepatic vascular resistance