Cardiac Cycle and Pressures Flashcards

1
Q

Steps of Cardiac Cycle

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

S1

A

Closure of AV valves, beginning of systole

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3
Q

S2

A

Passive closure of aortic, pulmonic valves

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4
Q

S3

A

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

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5
Q

S4

A

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

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6
Q

RA Pressures

A

0-2

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7
Q

RV Pressures

A

SAP 15-30, Diastolic 2-8

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8
Q

PAP

A

15mm Hg MAP

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9
Q

Pulmonary Capillaries

A

10mm Hg

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10
Q

Pulmonary Venous pressure

A

8mm Hg

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11
Q

LA P

A

2-5mm Hg

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12
Q

LV pressures

A

100-140 SAP
DAP 3-12

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13
Q

Aorta, large arteries

A

100mm Hg

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14
Q

Arterioles

A

50mm Hg

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15
Q

Capillaries

A

20mm Hg

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16
Q

Vena Cava

A

4mm Hg

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17
Q

Critical DO2

A

5-7mL/kg/min

18
Q

Critical HGB

A

4g/dL
Cyanosis at 5

19
Q

Critical O2ER

A

0.6(60%)

20
Q

CO - kidney

A

20-25%

21
Q

CO-liver

A

20-25%

22
Q

CO brain

A

10-15%

23
Q

CO heart (coronary BF)

A

5%

24
Q

CO - GIT

A

25%

25
Q

CO - skin

A

5%

26
Q

O2 ER: heart

A

10-12%

27
Q

O2 ER: SkM

A

2-5%

28
Q

O2ER kidney

A

2-3%

29
Q

O2ER:

A

GIT 4-6%

30
Q

Myocardial Oxygen Extraction

A

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

31
Q

L anterior descending coronary artery + branches

A

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

32
Q

Circumflex coronary artery

A

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

33
Q

Thebesian veins

A

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

34
Q

What determines BF to myocardium

A

extravascular compression of intramural coronary vessels (30-40% of total resistance), contractile state of myocardium, HR

Coronary blood flow determined by oxygen demand

35
Q

Cerebral Perfusion

A

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

36
Q

Bronchial Circulation

A

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

37
Q

Pulmonary Circulation

A

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

38
Q

HPV

A

 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

39
Q

Splanchnic Circulation

A

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

40
Q

Spleen

A

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

41
Q

Role of Axs in Splanchnic Circulation

A

blunt/abolish ability of splanchnic circulation to mobilize blood

42
Q

How Splanchnic vasculature mobilizes volume

A

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