CPR 23 - Cardiac Cycle

Question 1

Draw out the complete cardiac cycle graph with pressure and volume changes for the left atrium & ventricle, and aorta. Also include when the heart sounds appear and an ECG. Indicate when valves open and close.

Answer 1

Question 2

What is the dicrotic notch?

Answer 2

A sharp dip in aortic pressure followed by an increase in pressure as a result of the aortic valve closing.

Question 3

What is an “A” wave on a cardiac cycle graph?

Answer 3

The increase in atrial pressure seen just before the AV valves close due to atrial contraction

Question 4

What is the “C” wave on a cardiac cycle graph?

Answer 4

The increase in atrial pressure seen during ventricular contraction caused by an increase in ventricular wall tension that causes the mitral leaflets to bulge into the atrium

Question 5

What is a “X descent” on a cardiac cycle graph?

Answer 5

A decrease in atrial pressure seen after the “A” & “C” waves caused by ventricular ejection propeling the ventricles towards the apex away from the atria and pulling them open.

Question 6

What is a “V” wave on cardiac cycle graph?

Answer 6

A steady rise in atrial pressure during ventricular ejection due to blood filling up the atria.

Question 7

What is a “Y” descent on a cardiac cycle graph?

Answer 7

A sudden drop in atrial pressure after the mitral valve opens due to blood leaving the atrium.

Question 8

What is central venous pressure (CVP)?

Answer 8

Pressure in Vena Cava where it enters the RA

Question 9

List these pressures from largest to smallest: CVP, RA, peripheral venous pressure

Answer 9

Peripheral Venous Pressure > CVP > RA

Question 10

Answer 10

Question 11

How do systole and diastole change with increased HR?

Answer 11

Diastole time shortens significantly and Systole time shortens moderately.

Question 12

Answer 12

Question 13

What is the minimum type the heart requires to refill the ventricles adequately?

Answer 13

0.13s

Question 14

What do each of these sympathetic effects do: chronotropy, inotropy, lusitropy, dromotropy?

Answer 14

Question 15

Describe S1 and S2 and their causes.

Answer 15

S1 (lubb) - caused by closure of the AV valves which occurs at essentially the same time

S2 (dupp) - Closure of aortic and pulmonic valves. Upon inspiration the aortic valve closes BEFORE the pulmonic valve causing a S2 split.

Question 16

What does the S2 split indicate about heart blood flow?

Answer 16

That upon inspiration there is a transient drop in blood to the LA and increase in blood to the RA

Question 17

Why does inspiration cause an S2 split?

Answer 17

Inspiration causes a drop in intrathoracic pressure which increases venous return to the RA and RV which will delay valve closure. Inspiration also causes increased cross sectional area in the pulmonary system leading to a drop in blood return to the LA and LV causing the pulmonic valve to close early.

Question 18

What is the primary pathological reason that there is a split S1 or S2?

Answer 18

Conduction defects on one side of the heart

Question 19

What causes S3 and S4 and when do they normally occur?

Answer 19

S3 is caused by vibration of the ventricular walls which is caused by the rush of blood flow into the ventricles at the beginning of diastole, just after S2. It is common in young people and can indicate heart failure in the elderly.

S4 is also thought to be caused by vibration of the ventricular walls and AV valves but caused by atrial contraction at the end of diastole, just before S1. Often caused by disorders that cause resistance to ventricular filling

Question 20

What usually causes a heart murmur?

Answer 20

faulty valves

Question 21

What signs are indicative of aortic stenosis?

Answer 21

A crescendo-decresendo murmur from S1 to S2

Ventricular pressure is much higher than aortic

Question 22

What signs indicate aortic regurgitation?

Answer 22

A decrescendo murmur heard from S2 to S1.

A quick and sustained drop in aortic pressure during diastole leading to a water hammer pulse (Corrigan’s pulse, collapsing pulse) and an increased pulse pressure

Question 23

What signs indicate mitral stenosis?

Answer 23

An early diastolic opening snap heard followed by a rumble with a pre-systolic kick heard just before S1 (caused by atrial contraction).

LA pressure is always elevated above normal

Ventricular filling is reduced

Question 24

What signs indicate mitral regurgitation?

Answer 24

A pan systolic murmur (consistent intensity) between S1 and S2

A very tall “V” wave seen on cardiac cycle graph

Question 25

Answer 25