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Small Animal Medicine II > Normal Cardiac Anatomy & Physiology > Flashcards

Normal Cardiac Anatomy & Physiology Flashcards

1
Q

What is the normal anatomy of the canine and feline heart?

A
  • 4 chambers: 2 atria, 2 ventricles
  • 2 great vessels: aorta, pulmonary artery
  • 4 valves: tricuspid, mitral, pulmonic, aortic
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2
Q

What is cardiac conduction and function like?

A

electrical —> fill ventricles during diastole and eject during systole

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3
Q

What is cardiac output?

A

volume in liters pumped by the left ventricle each minute

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4
Q

How do the atria and ventricles compare?

A

ATRIA = reservoirs for ventricular filling during systole and conduits during diastole with a normal pressure of 0-12 mmHg

VENTRICLES = develop pressure necessary to open semilunar valves and expel blood into the great arteries

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5
Q

How do the right and left ventricles compare?

A

R = act as a bellow to eject blood into the pulmonary circulation at a relatively low pressure (0-8/15-25 mmHg)

L = conical-shaped chamber that must generate pressure 5-6x higher than pulmonary circulation at 4-12/110-130 mmHg) —> thicker myocardium

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6
Q

What happens in the ventricles during diastole?

A

both have very low pressure (<12 mmHg) and usually close to 0 mmHg

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7
Q

Heart chambers, pressure:

A
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8
Q

How does blood flow through the cardiovascular system?

A

arteries —> small arteries —> arterioles —> capillaries —> venules —> veins

  • each circuit delivers the same volume of blood each minute to the opposite side of the heart
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9
Q

What part of the cardiovascular system represents the major storage compartment of blood in the body?

A

veins

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10
Q

What determines blood pressure?

A

BP = CO x SVR

  • arterial pressure and vascular resistance are much higher on the systemic side
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11
Q

How does pulmonary veins’ limited capacity to store blood matter clinically?

A

increasing blood or plasma volume elevates venous pressure more rapidly in the pulmonary circulation than in the systemic circulation —> when the left heart fails, pressure builds up in the pulmonary circulation and results in fluid leaking out of the capillaries and into the interstitium = PULMONARY EDEMA

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12
Q

What kind of pressure system is pulmonary circulation? Why?

A

LOW - 15-25 mmHg systolic, 8-12 mmHg diastolic

allows for flow equal to systemic flow

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13
Q

At what 3 levels does pulmonary vascular resistance occur?

A
  1. left atrium
  2. arterioles, precapillary
  3. capillaries
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14
Q

What are some pre-capillary, capillary, and post-capillary causes of pulmonary hypertension?

A

arterial thromboembolism, reactive vasoconstriction

pulmonary parenchymal disease

left heart disease

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15
Q

What kind of pressure system is systemic circulation? Why?

A

HIGH - 110-140 mmHg systolic, 70-80 mmHg diastolic

high diastolic pressure must be maintained in the aorta so regional circulations can be perfused (CO is the same as the right ventricle = high systemic vascular resistance)

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16
Q

What is the major level of systemic vascular resistance?

A

arterioles

17
Q

What does persistent hypertension indicate?

A

abnormally high SVR or CO

18
Q

What is the cross-sectional area of pulmonary capillaries like? How does blood flow?

A

larger

flows slow to allow for gas exchange

(total blood in capillaries is small, much larger in veins)

19
Q

What determines CO?

A

CO = HR x SV (stroke volume)

20
Q

What is Ohm’s law?

A

flow = pressure difference / resistance

21
Q

If cardiac output remains the same, how does HR affect the heart?

A

determines how much it can fill

22
Q

What is blood pressure maintenance important for?

A

provides constant flow to vital organs

23
Q

What 7 things happen during systole?

A
  1. AV valves close (S1)
  2. ventricular depolarization
  3. isovolumetric contraction
  4. aortic/pulmonic valves open
  5. maximal/rapid ejection
  6. ventricular pressures fall with repolarization
  7. aortic and pulmonary valves close (S2, end of T wave)

systole = LV contraction

24
Q

What 6 things happen during diastole?

A
  1. isovolumetric relaxation, ventricular pressures drops
  2. atria fill with blood
  3. mitral valve opens
  4. LV fills rapidly
  5. slow LV filling (diastasis)
  6. atrial systole (kick)

diastole = LV relaxation

25
Q

What is diastolic function? What 3 things determine diastolic ventricular volume (preload)?

A

ability of the LV to fill with blood during diastole

  1. venous pressure
  2. atrial contraction
  3. properties of the ventricle
26
Q

What 2 things can reduce cardiac filling and preload?

A
  1. heart rhythm - shortened interval shortened by high HR
  2. atrial fibrillation - loss of atrial contraction reducing cardiac filling
27
Q

What 2 things does diastolic function determine?

A
  1. preload - ventricles relax, reduce intraluminal pressure, and fill
  2. coronary perfusion
28
Q

What diseases commonly limit ventricular filling?

A
  • decreased myocardial distensibility = hypertrophy, chamber dilation, myocardial fibrosis, myocardial ischemia
  • external compression = pericardial disease
29
Q

What 7 factors affect diastolic function?

A
  1. HR and rhythm - influences filling time
  2. atrial function - must contract correctly to fill ventricles
  3. pericardial function - heart must be able to relax and fill
  4. sympathetic activity - beta stimulation improves active relaxation
  5. venoconstriction and venous return - filling and preload
  6. ventricular wall thickness and compliance - ease of ventricle distention
  7. coronary perfusion - oxygen and energy needed for active relaxation
30
Q

What does systolic function determine? What 3 things does it depend on?

A

ventricular stroke volume —> what the heart can pump out

  1. preload
  2. contractility
  3. afterload
31
Q

What is preload? When does it decrease? Increase?

A

volume of blood in ventricles at the end of diastole

  • DECREASE - plasma volume loss (dehydration, diarrhea) reduces venous pressure (decreased CO)
  • INCREASE - increased circulating volume (fluid overload, fluid retention, regurgitation/shunting of blood)
32
Q

What is afterload? What happens when it’s high? What is it a major component of?

A

resistance in the aorta that the left ventricle must overcome to eject blood

limits the velocity and magnitude of ventricular contraction and decreases stroke volume

myocardial oxygen demand

33
Q

Preload vs. afterload:

A
34
Q

What is contractility? How is it measured?

A

ability of the myocardium to contract independently of change in preload or afterload

  • cardiac catheterization
  • echocardiogram
35
Q

What 3 factors can increase contractility?

A
  1. exercise
  2. adrenergic stimulation
  3. medication - Pimobendan, digitalis
36
Q

What is the Frank-Sterling Law?

A

increasing myocyte stretch leads to increased force of contraction in the normal heart, where stretch is directly related to preload of the ventricle or end diastolic volume (EDV)

  • helps heart compensate under normal stressful circumstances, but eventually it will not work in a failing heart

Small Animal Medicine II (57 decks)

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