Cardiac cycle Flashcards
What is an arterial line?
- Cannula straight into artery - hand or groin - monitors pressure
- Only used in intensive care
- Mean arterial = 80-90 mmHg
How to calculate MAP
Diastolic pressure + 1/3 of pulse pressure
How to perform cardiac catheterisation
- Find distal artery - cubital fossa or femoral and insert tube to heart
- Has pressure monitor and/or stent
Why is it beneficial that LV is thick walled and circular?
Generates greater pressure
What can increased pulmonary artery wedge pressure indicate?
Vasoconstriction, fluid overload, right to left shunt VSD, left ventricular failure, mitral valve failure, pulmonary hypertension
What can decreased pulmonary artery wedge pressure indicate?
Vasodilation and hypovolaemia
Right atrial pressure
- Fluid coming back into heart - lower pressure, less than 5/6 mmHg
- Equivalent to central venous pressure
- Seen clinically in jugular venous pulse
What do A, C, X, V and Y stand for in central venous pressure waveforms?
- 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
How to calculate cardiac output
Stroke volume x heart rate
What is ejection fraction?
Proportion of LVEDV that is ejected
How to calculate BP
Cardiac output x systemic vascular resistance
Coronary blood flow
- 250 mL/min (5% of cardiac output)
- O2 extraction rate - 55-60% at rest
- Autoregulates between MAP of 50-120 mm
What does the first sound indicate?
Closure of mitral and tricuspid valves
What does second sound indicate?
Closure of aortic and pulmonary valves
Does L or R valve close sooner?
L
