Cardiac Cycle

Question 1

What are the 5 stages in the heart cycle?

Answer 1

1. Late diastole: both sets of chambers are relaxed and ventricles fill passively
2. Atrial Systole: atrial contraction forces a small amount of additional blood into the ventricles.
3. Isovolumic Ventricular Contraction: first phase of ventricular contraction, pushes AV valves closed but does not create enough pressure to open the semilunar valves. the volume in the ventricle remains constant.
4. Ventricular Ejection: as ventricular pressure rises and exceeds pressure in arteries, semilunar valves open and blood is ejected.
5. Isovolumic ventricular relaxation: as ventricles relax pressure in ventricles fall, blood flows back into cups of semilunar valves and snaps them closed.

Question 2

How much of the cardiac cycle is ventricular diastole? ventricular systole? Atrial systole/diastole?

Answer 2

Ventricular systole: 1/3
Ventricular diastole: 2/3
Atrial systole: 1/4
Atrial diastole: 3/4

Question 3

Describe the electrical conduction of the heart.

Answer 3

1. SA node depolarization and rapid spread to AV node, depolarization throughout the atria is slower.
2. Conduction slows through the AV node and then rapidly through the HIS bundle, right and left bundle branches to/through the perkinje fibers at the apex of the heart.
3. depolarization wave spreads upward from the apex

Question 4

What is the cause of each of the following heart sounds…

• S1
• S2
• S2 split
• S3
• S4

Answer 4

• S1: AV valve closure/tensing, two components T1 and M1. M1 preceeds T1 slightly.
• S2: semilunar valves, two components: A2 and P2. A2 is louder and preceeds P2.

S2 Split: during inspiration this may be heard d/t increased venous return to the right side of the heart, greater volume of blood needing to be pumped out which takes longer leading to the pulmonic valve closing slightly after the aortic. This delay widens the time between A2 and P2.

• S3: results from rapid ventricular filling. “lub-dup-ta”
• S4: atrial contraction in the presence of a non-compliant ventricle. “ta-lub-dub”

Question 5

What populations might you hear S3?

Answer 5

S3 can be heard in children and young adults, typically those in great fitness, they possess a compliant ventricle.

S3 is also heard in adults(greater than 25yrs) with overload/heart failure, non-compliant ventricle.

Question 6

What popultaions migh you hear S4?

Answer 6

-common in elderly, this is never a normal sound.

Question 7

What position can S3 and S4 most commonly be heard?

Answer 7

Left lateral decubitus

Question 8

Which side of the stethoscope do we use to listen to high/low frequency?

Answer 8

High frequency: diaphragm

Low frequency: bell

Question 9

In a-fib you will never hear what heart sound?

Answer 9

S4

Question 10

What type of sound would you expect to hear with mitral stenosis? mitral prolapse?

Answer 10

stenosis: valve is stiff and hardly moves so S1 is softer.

Prolapse: valve is large and produces greater tension, louder S1

Question 11

What is the SInus of Valsalva?

Answer 11

located near the aortic root where blood pools in an eddie current during systole, in diastole the accumulated blood can flow into the coronary arteries.