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Cardiology Exam 1 > Hemodynamics > Flashcards

Hemodynamics Flashcards

1
Q

Properties of Arteries (3)

A
  • Large fluctuations in pressure (higher pulse pressure)
  • Thickest walls to withstand high surface tension
    • Tension = Pressure * Radius of Vessel
  • Compliance of arteries DEC w/ age so inc pulse pressure for a given SV (more fluctuation)
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2
Q

Properties of Arterioles

A

Major resistance vessels; largest amount of smooth muscle for resistance SO BP drops substantially in arterioles

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3
Q

Properties of Capillaries

A
  • Single layer of endothelial cells + basement membrane
  • HUGE SA
    * Velocity = Q/A so low velocity b/c huge area; good for exchange
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4
Q

Properties of Veins (3)

A
  • Much lower pressure (around 0)
    • Less pressure needed b/c lower resistance
    • Means there must be local generation of pressure
  • Thinner walls but larger diameter than arteries
  • VERY compliant (blood pulling esp when standing b/c gravity)
    • Compliance of veins INC w/ age
    • However, venous compliance dec w/ higher pressures and volumes
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5
Q

Ohm’s Law

A

Q= deltaP/R or deltaP= Q*R or R=deltaP/Q

So… flow inc if greater difference in pressure but dec if greater resistance

  • DeltaP is change in pressure from one end of vessel to other
  • For systemic circulation… deltaP = Paorta - Pright atrium = Paorta b/c Pright atrium almost 0 mmHg
  • For pulmonary circulation… deltaP = MeanPulmPress - Pleft atrium
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6
Q

TPR

A

Total Peripheral Resistance

  • one major factor is diameter of vessel (inc diameter = less R)
  • 1/Rtotal = 1/R1 + 1/R2 + 1/R3 etc (if 1, 2, 3 parallel pathways)
  • TPR is less than resistance in any one given vascular bed/pathway
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7
Q

Poiselle’s Law

A

Q = pideltaPr^4 / 8nl

  • r- radius of vessel (so change by vasoconstriction/dilation causes huge change in flow); so flow through capillary depends on radius of arteriole right in front of it
  • n- viscosity (higher if polycythemia and lower if anemic)
  • l - length of vessel
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8
Q

Reynold’s Number

A

Re = dvD/n

  • d- density of fluid; D- diameter of tube; v-velocity; n - viscosity
  • So larger vessels more likely to have turbulent flow (arteries)
  • Re> 1000 leads to turbulent flow (concentric motion NOT forward motion; frictional resistance; vibrations heard as murmurs)
  • Re < 1000 leads to laminar flow (fluid on inside moves faster b/c fluid on outside adheres to vessel wall - more prominent in small vessels)
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9
Q

Pulse Pressure & Compliance

A
  • Pulse Pressure = Systolic - Diastolic
  • Affected by compliance (tendency to resist recoil); greater compliance means greater storage of blood as potential energy so less fluctuation

C = deltaV/deltaP (more compliant means less change in pressure for given increase in volume of blood - b/c pool blood)

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10
Q

Mean Arterial Pressure

A

MAP = 2/3diastolicP + 1/3 systolicP

MAP = CO * TPR and CO = HR * SV so MAP = HR * SV * TPR

*If you inc resistance in some capillary beds/pathways… inc pressure in vessels prior to this increased resistance so inc pressure in other capillary beds/pathways

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11
Q

Surface Tension

A

Tension = Pr

* P- pressure against vessel wall 
* r- radius of vessel
  • So smaller vessel can withstand more pressure w/o breaking due to tension; aorta and other arteries have larger radius so need thicker wall to withstand greater surface tension
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12
Q

3 Mechanisms of Venous Return

A

1- Venous Valves
*If veins stretch (varicose veins) but valves do not stretch to same extent then valves do no adequately close)

2- Skeletal Muscle Pumping

3- Venomotor Tone
* vasoconstriction dec vein compliance/inc rigidity

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13
Q

Frank Starling Law of the Heart

A
  • Heart will always pump out as much blood as is returned to heart
  • Greater venous return —> myocardial cells stretched to optimal length or contraction —> greater force of contraction/greater stroke volume
    * Tension of contraction inc
    * Normally shorter than optimal length
    * Stretch also inc sensitivity of troponin to Ca++
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14
Q

Orthostatic Hypotension Mechanism

A
  • Postural change —> dec venous return —> dec CO —> dec MAP (lower BP)
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15
Q

5 Steps of Cardiac Cycle

A

1- Atria & ventricles in diastole - passive blood flow (80% vent blood)

2- Atria contract (last 20% vent blood)

3- Ventricles contract - forces tricuspid/mitral closed & aortic/pulmonic still closed - ISOVOLUMETRIC ventricular contraction

4- Ventricle ejection - now ventricular pressure high enough to open aortic/pulmonic valves to ventricular contraction —> ejection

5- Ventricles relax —> lower ventricle pressure —> causes retrograde flow back from artery into ventricles; causes aortic/pulmonic to snap shut & tricuspid/mitral still closed - ISOVOLUMETRIC ventricular relaxation ``

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16
Q

ESV and EDV

A

EDV - fullest ventricular volume; at end of atrial contraction

ESV- lowest ventricular volume; blood left in ventricle after ejection

17
Q

Ejection Fraction

A

EF = SV/EDV

18
Q

Terms to Describe Atrial Pressure Curve

A
  • a wave - atrial contraction
  • c wave - ventricular contraction - higher pressure caused by small back flow from ventricles when tricuspid closes & bulging of valve into atria when ventricle pressure inc
  • x descent - aortic/pulmonic valve opens relieving pressure on tricuspid/mitral valve
  • v wave - blood flow from veins to atrium during ventricular contraction (cannot leave atrium b/c tricuspid closed)
  • y descent - tricuspid/mitral opens to relieve pressure
19
Q

Which cells fire APs fastest? Which cells propogate APs fastest?

A
  • Rate of AP initial firing: SA node cells > AV node cells >bundle/Purkinje
  • Rate of AP conduction: Purkinje > atria inter-nodal > AV node (hence delay through AV node)
20
Q

4 Steps in Electrical Conduction

A

1- Depolarization starts at the SA node (R atrium near superior vena cava)

2- Non-contractile conducting cells carry impulse from SA node —> AV node (floor of R atrium) via inter-nodal fibers WHILE slow wave of depolarization sweeps across atria —> atria contract

3- DELAY b/c SLOW conduction through AV node but eventually travels to bundle of His
* Ensures atria contract BEFORE ventricles

4- Pulse carried by bundle branches —> apex of ventricles along ventricular septum —> back up Purkinje fibers —> depolarization spreads up from apex —> ventricles contract
* Starting from apex/bottom ensures blood is squeezed out top of ventricles

21
Q

4 Basic Heart Sounds

A
  • First - tricuspid/mitral valves close (start of ventricular systole)
  • Second - aortic/pulmonic (semilunar) valves close - start of ventricular diastole (retrograde flow closes valves)
  • Third - turbulent flow into ventricle near beginning of filling (diastole)
  • Fourth - additional turbulent flow into ventricle during atrial contraction (atrial systol

Cardiology Exam 1 (9 decks)

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