Basic Heart Sounds and Cardiac Cycle

Question 1

Define Systole and Diastole

Answer 1

Diastole: period of ventricular filling, “relaxation”
Systole: period of ventricular emptying, “contraction”

Question 2

Atrial systole:

Answer 2

small kick provided to ventricle at end of ventricular diastole

Question 3

Isovolumetric contraction:

Answer 3

marks start of ventricular systole
0.02-0.03 seconds
abrupt rise in ventricular pressure
no emptying (no change in volume)

Question 4

Period of rapid ejection

Answer 4

begins when pressure within ventricle > great artery (aorta or PA)
approximately first 1/3 of ejection time approx 70% of blood exits ventricle

Question 5

Period of reduced ejection

Answer 5

approximately 30% of emptying in last 2/3 of systole
ventricular pressure begins to fall to slightly < arterial pressure
ends in closure of aortic/pulm valves

Question 6

Isovolumetric relaxation

Answer 6

rapid relaxation and decrease in ventricular pressure
0.03-0.06 seconds
ends when ventricular pressure falls to less than corresponding atrium

Question 7

Rapid ventricular filling

Answer 7

atrial volumes and pressures increased
AV valves open
ventricles easily relax
most filling is early in diastole (first 1/3)

Question 8

Diastasis

Answer 8

reduced ventricular filling
blood that continues to empty into atria from veins - passes directly into ventricles
Relative inactivity
ends with atrial systole

Question 9

Discuss the relationship between ECG, ventricular pressure, and the generation of arterial blood pressure.

Answer 9

• Pventricle > Partery
  
  • aortic and pulmonary valves open
  • entry of blood into arteries causes increase in pressure and increase in arterial wall tension
  • Pressure increases in arteries
  • After QRS complez
• Elastic recoil
  
  • Partery > Pventricle
  • kinetic energy of blood’s momentum converted into pressure in the aorta
  • Ventricles continue to empty while pressure falls
  • Ventricles repolarize: T wave
• Dicrotic notch (incisura)
  
  • notch in aortic pressure curve
  • short period of blood backflow followed by sudden cessation with aortic valve closure
  • end of T wave

Question 10

Describe left atrial pressure during each phase of the cardiac cycle.

Answer 10

• a wave:
  
  • Immediately follows the p wave of ECG
  • Caused by atrial contraction
  • RAP 4-6 mmHg
  • LAP 7-8 mmHg
• c Wave
  
  • After QRS
  • onset of ventricular contraction
  • backward bulge of AV valves
• x descent
  
  • with ventricular emptying, thoracic volume and pressure fall
  • rapid fall in atrial pressure
• v wave
  
  • near end of ventricular systole
  • flow of blood into atria from veins
  • AV valves are closed
• y descent
  
  • atria drain rapidly into ventricles
  • rapid fall in atrial pressure

Question 11

Identify each of the four major heart sounds and associate them with a functional cause for the sound.

Answer 11

• Valves opening usually are quiet. Valves closing cause vibrations (noise)
• Always heard: S1 and S2
• Sometimes heard: S3 and S4
• S1: Slow low pitched vibration
  
  • Closing of A-V valve
• S2: rapid, high frequency “snap”
  
  • closure of aortic and pulmonary valves
• S3: Vibrations caused by rapid ventricular filling
• S4: infrequently heard
  
  • atrial contraction

Question 12

Assess the development of venous pulse waves.

Answer 12

• transducer over the jugular vein records changes in venous pressures
• Atrial contraction generates increase in venous pressure
  
  • the “a” wave
  • following the ECG P wave
• initial ventricular contraction
  
  • the “c” wave is generated
  • corresponds to bulging of the AV valves back into the atria.
• atria and vein filling while the AV valve is still closed (systole)
  
  • the “v” wave.

Question 13

Volume-Flow Relationship

Answer 13

• end diastolic volume (EDV)
  
  • The ventricular volume at the end of filling
  • 110-120mmHg in the adult during normal conditions.
• end systolic volume (ESV)
  
  • end of systole, the ventricle achieves its smallest volume
  • 40-50 ml in the adult.
• stroke volume (SV)
  
  • the amount ejected during systole
  • (SV) = EDV - ESV
• ejection fraction (EF)
  
  • amount of blood ejected, when designated as a percent of the end diastolic volume

Question 14

Function of Cardiac valves

Answer 14

• four cardiac valves function passively
• dictated by the pressure differences across the valves.
• work to prevent the backflow of blood when the backward pressure gradient pushes blood backwards.
• open when a forward pressure gradient forces blood in the forward direction

Question 15

Atrioventricular Valves

Answer 15

• Tricuspid and mitral valves
• attached to papillary muscles on the inner surface of the ventricular muscle by fibrous tissue called chordae tendinae
• papillary muscles contract during systole
  
  • prevent the AV valves from bulging backward into the atria
• Injury to the papillary muscles or chordae tendinae may result in severe leakage (insufficiency) of the AV valves
  
  • can lead to severe cardiac dysfunction.

Question 16

The semilunar valves

Answer 16

• three thin concave cusps which coapt centrally.
• semilunar valve diameter is much smaller than AV valves.
  
  • results in a higher velocity of bloodflow across the valve
  • higher mechanical abrasion.
• Because of relatively high arterial pressures, the semilunar valves close more abruptly (“snap”) than the atrioventricular valves.

Question 17

List the sequence of valve opening and closing in the right and left heart.

Answer 17

• first heart sound due to vibrations from the closing AV valves
• mitral valve closes slightly earlier than the tricuspid valve
  
  • the human ear usually cannot distinguish any difference.
  • because AV valve closure is low pitched and occurs slowly
• semilunar valve closure is higher pitched and more “snappy”
• Aortic valve closure typically occurs before pulmonary valve.
• This difference is readily apparent on physical examination and results in “splitting” of the second heart sound.