Cardiology Flashcards

1
Q

Define preload

A

The force imposed on a resting muscle that stretches the muscle to a new length.

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2
Q

What principle is described in the definition

The force imposed on a resting muscle that stretches the muscle to a new length.

A

Preload

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3
Q

What determines preload in the heart

A

End diastolic ventricular volume

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4
Q

State the Frank-Starling relationship

A

In the normal heart, diastolic volume is the principle factor governing the strength of ventricular contraction

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5
Q

What surrogate measure is used in clincal practice to estimate right ventricular end-diastolic volume (and therefore preload)?

A

Central venous pressure

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6
Q

What surrogate marker is used to estimate left ventricular end-diastolic volume in clinical practice?

A

Pulmonary artery occlusion pressure

NB: pulmonary artery wedge pressure is a misnomer unless catheter is actually being wedged into capillaries

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7
Q

What equation describes ventricular compliance?

A

Compliance = ∆EDV / ∆EDP

Where EDV = end diastolic volume; EDP = end-diastolic pressure

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8
Q

How will decreased ventricular compliance affect the estimation of end-diastolic ventricular volume by measurement of end-diastolic pressure?

A

It will cause an overestimation of end-diastolic volume

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9
Q

Contrast heart failure with normal and reduced ejection fractions in terms of:

  • end diastolic pressure
  • end diastolic volume
A

Preserved ejection fraction:

  • high EDP
  • low EDV

Reduced ejection fraction:

  • high EDP
  • high EDV
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10
Q

Define afterload

A

The force equivalent to the peak tension developed across the walls of the ventricle during systole

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11
Q

State the Laplace equation.

A

Wall tension = (pressure x radius) / (2 x wall thickness)

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12
Q

What four factors contribute to ventricular afterload?

A
  1. Pleural pressure
  2. End diastolic volume
  3. Aortic impedance
  4. Systemic vascular resistance
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13
Q

What is vascular impedance?

A

The force that opposes the rate of change in pressure and flow; that is, the force that opposes pulsatile flow.

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14
Q

What vessels predominantly determine vascular impedance?

A

Proximal arteries (e.g., aorta, pulmonary arteries)

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15
Q

What vessels determine vascular resistance?

A

Arterioles, capillaries

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16
Q

What is vascular resistance?

A

The force opposing non-pulsatile flow.

17
Q

State the general equation describing resistance to flow in a hydraulic circuit

A

R = (PIN - POUT) / Q

Where R = resistance; Q = flow

18
Q

State the equation describing systemic vascular resistance

A

R = (MAP - CVP) / CO

19
Q

State the equation describing pulmonary vascular resistance

A

R = PAP - LAP / CO

20
Q

What equation describes the determinants of steady flow through small tubes

A

Hagen-Pouseuille equation

(Q = ∆P x (πr4/8µL)

21
Q

State the equation describing resistance to flow in small tubes

A

R = 8µL / πr4

Where R = resistance; µ = viscosity; L = tube lenght; r = tube radius

22
Q

What is the effect of positive pleural pressure on ventricular emptying?

A

Increased emptying

23
Q

What is the effect of negative pleural pressure on ventricular emptying?

A

Reduced ventricular emptying

24
Q

What component force affecting ventricular afterload cannot be measured?

A

Vascular impedance

25
At what phase of respiration should central venous pressure be transduced?
End expiration
26
When measuring CVP in ventillated patients, what ventillator setting must be accounted for?
positive end expiratory pressure (PEEP
27
What four factors cause a right shift in the oxyhaemoglobin dissociation curve? What is the consequence of this?
1. Acidaemia 2. High temperature 3. Decreased CO2 4. Increased 2,3 DPG Consequence: reduced oxygen-haemoglobin affinity for a given PO2
28
What five factors cause a left shift in the oxyhaemoglobin dissociation curve? What is the effect of left shift?
1. Alkalaemia 2. Low temperature 3. Decreased CO2 4. Decreased 2,3 DPG 5. Increased CO Effect: increased affinity betwen oxygen and haemoglobin for a given pO2
29
Define the Bohr effect
Haemoglobin oxygen-binding capacity is inversely related to the acidity and the partial pressure of COin the solution
30
State the equation describing haemoglobin-bound oxygen content in blood
HbO2 = 1.34 x [Hb] x SO2
31
State the equation describing dissolved oxygen content in blood
Dissolved O2 = 0.003 x pO2 (mL/dL)
32
State the equation describing arterial oxygen content
CaO2 = (1.34 x [Hb] x SaO2) + (0.003 x PaO2)
33
Define dysoxia
The state where nutrient metabolism is limited by the availability of oxygen
34
What are the two causes of dysoxia?
1. Hypoxia (inadequate supply to tissues) 2. Cytopathic hypoxia (defective oxygen utilization)
35
What adrenergic receptors predominate myocardium?
Beta 1
36
What are the diagnostic criteria for systemic inflammatory response syndrome (SIRS)
At least two of: * Resp. rate \>20 or PCO2 \<32mmHg * Pulse \>90 beats/min * Temperature \>38 or \<36 * WCC \>12x103/mm3, \<4x103/mm3; or \>10% immature neutrophils
37
Define sepsis
SIRS plus evidence of infection
38
Define is Wellens' syndrome?
Wellens’ syndrome is a pattern of **deeply inverted or biphasic T waves** in V2-3, which is highly specific for a critical stenosis of the left anterior descending artery (LAD)
39
What are the Brugada criteria? Describe them.
For differentiating SVT with aberrancy and VT