Cardiac cycle

Question 1

What is an arterial line?

Answer 1

• Cannula straight into artery - hand or groin - monitors pressure
• Only used in intensive care
• Mean arterial = 80-90 mmHg

Question 2

How to calculate MAP

Answer 2

Diastolic pressure + 1/3 of pulse pressure

Question 3

How to perform cardiac catheterisation

Answer 3

• Find distal artery - cubital fossa or femoral and insert tube to heart
• Has pressure monitor and/or stent

Question 4

Why is it beneficial that LV is thick walled and circular?

Answer 4

Generates greater pressure

Question 5

What can increased pulmonary artery wedge pressure indicate?

Answer 5

Vasoconstriction, fluid overload, right to left shunt VSD, left ventricular failure, mitral valve failure, pulmonary hypertension

Question 6

What can decreased pulmonary artery wedge pressure indicate?

Answer 6

Vasodilation and hypovolaemia

Question 7

Right atrial pressure

Answer 7

• Fluid coming back into heart - lower pressure, less than 5/6 mmHg
• Equivalent to central venous pressure
• Seen clinically in jugular venous pulse

Question 8

What do A, C, X, V and Y stand for in central venous pressure waveforms?

Answer 8

• A: atrial contraction
• C: tricuspid valve bulging back into RA
• X: atrial relaxation
• V: atrial filling with closed tricuspid valve
• Y: atria empties into ventricle

Question 9

How to calculate cardiac output

Answer 9

Stroke volume x heart rate

Question 10

What is ejection fraction?

Answer 10

Proportion of LVEDV that is ejected

Question 11

How to calculate BP

Answer 11

Cardiac output x systemic vascular resistance

Question 12

Coronary blood flow

Answer 12

• 250 mL/min (5% of cardiac output)
• O2 extraction rate - 55-60% at rest
• Autoregulates between MAP of 50-120 mm

Question 13

What does the first sound indicate?

Answer 13

Closure of mitral and tricuspid valves

Question 14

What does second sound indicate?

Answer 14

Closure of aortic and pulmonary valves

Question 15

Does L or R valve close sooner?

Answer 15

L

Question 16

What are heart murmurs?

Answer 16

• 250 mL/min (5% of cardiac output)
• O2 extraction rate - 55-60% at rest
• Autoregulates between MAP of 50-120 mm

Question 17

What are valvular murmurs?

Answer 17

• Stenotic valve: stiff or narrowed valve that doesn’t open completely - blood forced through narrowed opening (ejection murmur)
• Regurgitant (incompetent) valve: valve edges are scarred - don’t close completely - backflow of blood, lower frequency