Hemodynamics

Question 1

Five steps of the cardiac cycle

Answer 1

• Systole:
  
  • Isovolumic contraction
  • Ejection
• Diastole
  
  • Isovolumic relaxation
  • Passive filling
  • Active filling

Question 2

What happens at each of the steps?

• Systole:
  
  • Isovolumic contraction
  • Ejection
• Diastole
  
  • Isovolumic relaxation
  • Passive filling
  • Active filling

Answer 2

• Systole:
  
  • Isovolumic contraction
    
    • volume doesnt change, walls squeeze - increase Pressure
  • Ejection
    
    • Pressure > Paorta/Ppulmonary = valves open
• Diastole
  
  • Isovolumic relaxation
    
    • all valves closed
    • pressure drops
    • AV valves open
  • Passive filling - no contraction
  • Active filling
    
    • atria contract to send remaining blood into ventricle to fill completely

Question 3

How to calculate cardiac output?

Answer 3

C.O. = SV x HR

Question 4

What are the lub dub sounds of the heart

Answer 4

1st sound - when AV valves close at beginning of systole (isovolumetric contraction)

2nd sound - when Semilunar valves close; beginning of ventricular diastole

Question 5

How to calculate stroke volume?

Answer 5

Stroke volume = EDV - ESV

Question 6

What is ESPVR?

Answer 6

the relation between pressure and volume in the left or right ventricle when the myocardium reaches its maximum state of activation near end-systole

• contractility of the heart

Shift left on Pressure volume loop = increase contraction

Question 7

What is EDPVR?

Answer 7

End Diastolic Pressure Volume Relationship (EDPVR) relates to the passive filling curve of the left ventricle during diastole and is a measure of passive chamber stiffness. The slope of EDPVR is the reciprocal of compliance and is used to measure ventricular stiffness.

Question 8

Effect of a inotropic agent (pos or neg) on ESPVR

Answer 8

Pos inotropy - increase contractility = increase SV = shift left

Neg inotropy - decrease SV = shift right

Question 9

What limits the length - dependent increase in force of contraction?

Answer 9

Favourable sarcomere length

• too much stretch = actin/myosin slippage

Question 10

What happens to EDPVR when heart stiffens?

Answer 10

Pressure increases overall -> Loop moves right -> pos increase so slope increases

ie MOVES UP on Pressure-volume loop