Cardiac Cycle And Performance

Question 1

Atrial Systole is represented by what on the ECG?

Answer 1

P wave.

Question 2

Briefly describe the events of atrial systole.

Answer 2

Atria contracts, The mitral valves open, blood rushes from atrium into ventricles causing an increase in ventricular pressure.

Question 3

Relating to heart sound, what is S1?

Answer 3

S1 is the Lub of a normal heartbeat. It occurs during the closure of the mitral and tricuspid valves (AV valves).

Question 4

Relating to heart sound, what is S2?

Answer 4

S2 is the dub of the normal heartbeat. It is the closure of the aortic and pulmonary valves.

Question 5

Which part of am ECG is represented by the isovolumetric ventricular contraction?

Answer 5

QRS complex

Question 6

Briefly describe isovolumetric ventricular contraction (B)

Answer 6

Includes the left ventricle contracting and the mitral and tricuspid valve closing. Once closed, ventricular pressure increases drastically but the ventricle volume remains constant due to the valves being closed.

Question 7

Describe Part C of the cardiac cycle.

Answer 7

C is referred to as the Rapid ventricular ejection. This is where the ventricles continue to contract until maximum.
Once he ventricle pressure > aortic pressure, the aortic valves open and blood then rushes into the aorta.
Ventricle pressures decreases and aortic pressure increases. The atria pressure then slowly begins to increase.

Part C is represented as the end of the ST segment on a ECG.

Question 8

Describe part D of the cardiac cycle.

Answer 8

D refers to as the reduced ventricular ejection.
This is where the ventricles pushed blood into the arteries. Ventricle pressure and volume decreases

D represents the T wave on an ECG.

Question 9

Describe part E of the cardiac cycle.

Answer 9

E refers to as the Isometric volume relaxation. Once ventricle pressure is < aortic pressure, the aortic valve closes.
Once the aortic valve close is produces a dicrotic notch

Represents the end of the T wave

Question 10

Describe part F & G of the cardiac cycle.

Answer 10

F & G represents Rapid and Reduced ventricular fillings.
F- Rapid ventricular filling - ventricles is relaxed. Once left ventricle reaches slight below atria pressure, the mitral valve opens and the same process is repeated as Part A.
G- Reduced ventricular fillings- ventricles relaxed. Longest part of the cardiac cycle.

Question 11

When inotrophy is increased, what is the effect on the frank sterling curve?

Answer 11

When increased, the FS curve shifts up and to the left. There is an increase in SV and a decrease in LVEDP.

Question 12

When inotrophy is decreased, what is the effect on the frank sterling curve?

Answer 12

When there is a decreased, the FS curve shifts down resulting in an decrease in SV and a increase in LVEDP.

Question 13

Discuss how the preload, afterload and contractility affect cardiac output.

Answer 13

If Preload and contractility increases, SV increases therefore increase CO
If Afterload increases, SV decreases and CO decreases.

Question 14

Explain the stages of the ventricular volume- pressure loop.

Answer 14

(4-1) Ventricular filling -> mitral valves closes -> Isovolumetric contraction (1-2) -> Aortic valves open -> Ventricular ejection (2-3) -> Aortic valves closes -> Isovolumetric relaxation (3-4) -> Mitral valves open

Question 15

What effect does the afterload have on the stroke volume of the ventricular volume pressure loop?

Answer 15

Once the afterload increases, the stroke volume decreases, and aortic pressure increases.

Question 16

What effect does the preload have on the stroke volume of the ventricular volume pressure loop?

Answer 16

If the preload increases, SV increases.

Question 17

What effect does the contractility have on the stroke volume of the ventricular volume pressure loop?

Answer 17

In contractility increases, SV increases and ESV decreases

Question 18

What caused the spilling of the second heart (S4) sounds?

Answer 18

When the aortic valve closes before the pulmonary valve.

A delay in the closing of the pulmonary valve.

Question 19

State the significance/ effect of digitalis (Digoxin).

Answer 19

It inhibits the Na/K+-ATP — increases intercellular NA+ — decreases the NA+ gradient — increases the intercellular Ca2+ via the Na+-Ca++ exchanger.

Question 20

List positive intropic factors.

Answer 20

— NE
— HR
— Drugs ex. Digitalis (Digoxin)
— Epinephrine
— ECF Ca2+

Note: these factors increase contractility.

Question 21

List negative intropic factors.

Answer 21

— AcH and cholinergic agonists
— B- blockers (Propranolol, atenolol)
— Ca channel blockers
— Removal of Ca2+ from ECF
— Acidosis & hypoxia
— HF

Note: these factors decrease contractility.