Cardiac Output

Question 1

What is cardiac output?

Answer 1

It is the volume of blood pumped out off the heart in 1 min.

Question 2

What is the equation for cardiac output?

Answer 2

Cardiac output (CO) = Stroke volume (SV) x Heart rate (HR)

Question 3

What it is the Stroke volume and which are its equations?

Answer 3

It is the mean of blood put out of the heart with each heart beat.
SV= CO/HR. SV= End-diastolic volume - End-systolic volume.

Question 4

What is the Fick principle or Fick Equation?

Answer 4

CO= Rate of O2 consumption / Arterial O2 content - Venous O2 content.

Question 5

What is the equation of Mean Arterial Pressure?

Answer 5

Mean Arterial Pressure (P) = Cardiac output (Q) x Peripheral Resistance (R). P=QxR

Question 6

What is the following equation belong?

2/3 of diastolic pressure + 1/3 of systolic pressure.

Answer 6

Mean arterial pressure.

Question 7

What is the equation for pulse pressure?

Answer 7

Pulse pressure = Systolic pressure - Diastolic pressure.

Normal: 40-60

Question 8

Which are the characteristics of the cardiac output during exercise?

Answer 8

Initially: high cardiac output to high stroke volume.

Sustained exercise: cardiac output maintained due to high heart rate.

Question 9

What situation cardiac output goes down?

Answer 9

Cardiac Output goes down if Heart rate is too high.

Atrial Fibrillation and Ventricular Tachycardia = decreased Cardiac Output.

Question 10

What is the preload and which are the measurement of the preload?

Answer 10

It is the pressure at End-Diastolic Volume.

Atrial pressure, End-diastolic pressure, central venous pressure.

Question 11

What is the afterload?

Answer 11

It is the Mean Arterial Pressure, total peripheral resistance (TPR).

Question 12

Which are the situation where preload can increase?

Answer 12

Exercise, increase blood volume ( over- transfusion, over- hydration, pregnancy)

Question 13

What drugs decrease preload?

Answer 13

Venodilators:

- Nitrates (nitroglycerin).

Question 14

What drugs decrease afterload?

Answer 14

Vasodilators:

- Hydralazine.

Question 15

What affects stroke volume?

Answer 15

Contractility, increasing preload (decrease Stroke volume), increasing afterload (increase stroke volume), ejection fraction.

Question 16

What increase contractility and stroke volume?

Answer 16

Catecholamines.
Beta 1 receptors: increase activity in the calcium pump (sarcoplasmic reticulum). Increase calcium that increase contractility.

Question 17

What decreased contractility?

Answer 17

Beta 1 blockade.
Heart failure.
Acidosis.
Hypoxia.
Hypercapnia.
Non-Dihydropyridine CCBs.

Question 18

Which substances increase the contractility?

Answer 18

Catecholamines and positive inotropes (e.g., digoxin).

Question 19

What cases decrease Contractility?

Answer 19

Loss of myocardium, B-blockers (acutely), non-Dihydropyridine Ca2+ channel blockers, dilated cardiomyopathy.

Question 20

What is the equation for Ejection Fraction and what is the normal percentage of EF?

Answer 20

EF= SV/EDV and over 55%

Question 21

What is the relation between viscosity and resistance?

Answer 21

Increase viscosity = increase resistance.

Ex. Polycythemia, hyperproteinemic state (multiple myeloma), Hereditary spherocytosis.

Question 22

What is the pulse pressure in a patient with systolic blood pressure an 150 and mean arterial pressure an 90?

Answer 22

Pulse pressure 90

Question 23

What is the base equation for cardiac output?

Answer 23

CO = SV x Heart rate.

Question 24

What is the Fick principle?

Answer 24

CO = Rate of O2 consumption / Arterial O2 content - Venous O2 content.

Question 25

How can the myocardial oxygen demand be decreased in circumstance where the heart is ischemic?

Answer 25

Decrease afterload (B-blockers), decrease contractility (B-blockers) and heart rate (B-blockers or CCB).

Question 26

What can make the stroke volume increase for a given preload?

Answer 26

Increase contractility or Intropy: Sympathetic stimulation, inotropic drugs (catecholamines, digoxin), increase intracellular calcium, decrease extracelular sodium.

Question 27

What factors affect stroke volume?

Answer 27

Afterload, preload, contractility.

Question 28

What is the heart ejection fraction (EF)?

Answer 28

EF = SV/EDV.

Question 29

Describe the function of sarcomere:

Answer 29

Contractile unit.

Question 30

Describe the function of intercalated disks:

Answer 30

Cell adhesion.

Question 31

Describe the function of Gap junction:

Answer 31

Electrochemical communication between myocardial fibers.

Question 32

Describe the function of Sarcoplasmic reticulum:

Answer 32

Storage and release of calcium.

Question 33

Which ion determines the magnitude of tension in a contracting myocardial cell?

Answer 33

Amount of intracellular calcium.

Question 34

Describe the effect of increased heart rate:

Answer 34

Increased contractility.

Question 35

Describe the effect of the catecholamines?

Answer 35

Increased contractility.

Question 36

Describe the effect of the Digoxin?

Answer 36

Increase contractility.

Question 37

Describe the effect of the Acetylcholine (ACh)?

Answer 37

Decreased contractility.

Question 38

What is the Frank-Starling relationship?

Answer 38

The greater the End-diastolic volume (preload), the greater is the stroke volume (SV).

Question 39

How does contractility affect cardiac output?

Answer 39

Cardiac output increases as contractility increases.

Question 40

Name the four factors that determine myocardial oxygen consumption?

Answer 40

1-Afterload. 2-Size of heart (wall tension). 3-Contractility. 4-Heart rate.