Cardiac Mechanical

Question 1

Timing of Systole and diastole

Answer 1

1. Atrial systole- squeezes the last bit of blood into the ventricle
2. Atrial diastole begins
3. Ventricular systole first phase
   
   1. contraction force pushes AV valves closed but not enough force to open semilunar valves
4. Ventricular systole second phase
   
   1. pressure rises to exceed pressure of the arteries and semilunar valves open and blood is ejected
5. Ventricular diastole, early
   
   1. ventricles relax, pressure drops, blood flows back agains semilunar valves, closing them.
   2. blood flows into the relaxed atria
6. Ventricular diastole, late
   
   1. all chambers are relaxed, ventricles fill passively

Question 2

What are the three major events of ventricular diastole?

Answer 2

1. Early diastole: pressure dropping and semilunar valves closing. Pressure less than arteries but more than atria.
2. Late diastole: Pressure drops below atri, AV valve opens. Rapid ventricular filling passively
3. Atrial systole: atrial contraction tops off the last bit of blood into ventricle

Question 3

What is the approximate End Diastolic Volume?

Answer 3

about 120 ml in ventricles

Question 4

What are the two major events of systole?

Answer 4

1. First phase
   
   1. isovolumetric contraction, pressure increase, valves closed.
   2. pressure rises until ventricular pressure exceeds aortic pressure and valve opens
2. Second phase
   
   1. Semilunar valves open
   2. rapid ejection followed by reduced ejection as ventricular pressure falls

Question 5

Normal intracardiac pressures of PA

Answer 5

Systolic: 15-30 mmHg

Diastolic: 3-12 mmHg

Question 6

Normal intracardiac pressure RA

Answer 6

0-8 mmHg

nickel

Question 7

Normal intracardiac pressures RV

Answer 7

Systolic: 15-28 mmHg

End-Diastolic: 0-8 mmHg

Quarter/nickel

Question 8

Normal Intracardiac pressures Aorta

Answer 8

Systolic: 96-140 mmHg

Diastolic: 60-90 mmHg

Question 9

Normal intracardiac pressure LA

Answer 9

4-12 mmHg

dime

Question 10

Normal intracardiac pressures LV

Answer 10

Systole: 90-140 mmHg

Diastole: 4-12 mmHg

1.25/dime

Question 11

Normal intracardiac pressure in Pulmonary Vein

Answer 11

about 9 mmHg

dime

Question 12

Heart Sounds

S1

Answer 12

“Lubb”

closure of AV valves

Question 13

Heart Sounds

S2

Answer 13

“dubb”

closure of semilunar valves

Question 14

Heart Sounds

S3

Answer 14

rapid passive filling

*not normally heard in adults; may be heard in small children or endurance athletes

Question 15

Heart Sounds

S4

Answer 15

atrial systole

normally not heard in adults

Question 16

Murmur

Answer 16

gurgling sound as blood moves through damaged valves

Question 17

bruit

Answer 17

abnormal sound as blood runs past and obstruction through arteries

Question 18

Factors that affect cardiac output

Answer 18

CO = SV x HR

Heart rate

Stroke volume: Preload, contractility, afterload

Question 19

inotropic

Answer 19

related to strength of contraction

Question 20

chronotropic

Answer 20

related to speed of contractions

Question 21

How does the Autonomic nervous system alter HR?

Answer 21

• Sympathetic:
  
  • NE/Epi
  • Beta 1 receptors
  • positive chronotropic effect
• Parasympathetic:
  
  • Acetylcholine
  • M2 receptor
  • negative chronotropic effect

Question 22

What are the two main mechanisms for altering stroke volume?

Answer 22

Intrinsic regulation

Autonomic regulation

Question 23

Intrinsic regulation of stroke volume

Answer 23

• Frank-Starling law of the heart
  
  • increased stretch of myocytes increases strength of contraction
  • by more optimally lining up the myosin and actin so more can “grab” hold
  • increased stretch created by increase in venous return and EDV

Question 24

Autonomic regulation of stroke volume

Answer 24

• Contractility
  
  • increased strength of contraction due to increased amount of cytosolic calcium (primarily SNS)
  • NE increases Ca++

Question 25

positive inotropes

Answer 25

increase contractility

epi/NE

Question 26

negative inotropes

Answer 26

decrease contractility

drugs: beta blockers, Calcium channel blockers

Question 27

Ejection fraction equation

Answer 27

EF = SV/EDV