Cardiology

Question 1

Define preload

Answer 1

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

Question 2

What principle is described in the definition

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

Answer 2

Preload

Question 3

What determines preload in the heart

Answer 3

End diastolic ventricular volume

Question 4

State the Frank-Starling relationship

Answer 4

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

Question 5

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

Answer 5

Central venous pressure

Question 6

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

Answer 6

Pulmonary artery occlusion pressure

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

Question 7

What equation describes ventricular compliance?

Answer 7

Compliance = ∆EDV / ∆EDP

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

Question 8

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

Answer 8

It will cause an overestimation of end-diastolic volume

Question 9

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

• end diastolic pressure
• end diastolic volume

Answer 9

Preserved ejection fraction:

• high EDP
• low EDV

Reduced ejection fraction:

• high EDP
• high EDV

Question 10

Define afterload

Answer 10

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

Question 11

State the Laplace equation.

Answer 11

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

Question 12

What four factors contribute to ventricular afterload?

Answer 12

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

Question 13

What is vascular impedance?

Answer 13

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

Question 14

What vessels predominantly determine vascular impedance?

Answer 14

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

Question 15

What vessels determine vascular resistance?

Answer 15

Arterioles, capillaries

Question 16

What is vascular resistance?

Answer 16

The force opposing non-pulsatile flow.

Question 17

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

Answer 17

R = (P_IN - P_OUT) / Q

Where R = resistance; Q = flow

Question 18

State the equation describing systemic vascular resistance

Answer 18

R = (MAP - CVP) / CO

Question 19

State the equation describing pulmonary vascular resistance

Answer 19

R = PAP - LAP / CO

Question 20

What equation describes the determinants of steady flow through small tubes

Answer 20

Hagen-Pouseuille equation

(Q = ∆P x (πr⁴/8µL)

Question 21

State the equation describing resistance to flow in small tubes

Answer 21

R = 8µL / πr⁴

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

Question 22

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

Answer 22

Increased emptying

Question 23

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

Answer 23

Reduced ventricular emptying

Question 24

What component force affecting ventricular afterload cannot be measured?

Answer 24

Vascular impedance

Question 25

At what phase of respiration should central venous pressure be transduced?

Answer 25

End expiration

Question 26

When measuring CVP in ventillated patients, what ventillator setting must be accounted for?

Answer 26

positive end expiratory pressure (PEEP

Question 27

What four factors cause a right shift in the oxyhaemoglobin dissociation curve? What is the consequence of this?

Answer 27

1. Acidaemia
2. High temperature
3. Decreased CO₂
4. Increased 2,3 DPG

Consequence: reduced oxygen-haemoglobin affinity for a given PO₂

Question 28

What five factors cause a left shift in the oxyhaemoglobin dissociation curve? What is the effect of left shift?

Answer 28

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

Question 29

Define the Bohr effect

Answer 29

Haemoglobin oxygen-binding capacity is inversely related to the acidity and the partial pressure of CO₂in the solution

Question 30

State the equation describing haemoglobin-bound oxygen content in blood

Answer 30

HbO₂ = 1.34 x [Hb] x SO₂

Question 31

State the equation describing dissolved oxygen content in blood

Answer 31

Dissolved O₂ = 0.003 x pO₂ (mL/dL)

Question 32

State the equation describing arterial oxygen content

Answer 32

CaO₂ = (1.34 x [Hb] x SaO₂) + (0.003 x PaO₂)

Question 33

Define dysoxia

Answer 33

The state where nutrient metabolism is limited by the availability of oxygen

Question 34

What are the two causes of dysoxia?

Answer 34

1. Hypoxia (inadequate supply to tissues)
2. Cytopathic hypoxia (defective oxygen utilization)

Question 35

What adrenergic receptors predominate myocardium?

Answer 35

Beta 1

Question 36

What are the diagnostic criteria for systemic inflammatory response syndrome (SIRS)

Answer 36

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

Question 37

Define sepsis

Answer 37

SIRS plus evidence of infection

Question 38

Define is Wellens’ syndrome?

Answer 38

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)

Question 39

What are the Brugada criteria? Describe them.

Answer 39

For differentiating SVT with aberrancy and VT