Week 4 Pre-Learning: Perfusion Properties

Question 1

What are the 5 mechanical properties affecting cardiac output?

Answer 1

1. Cardiac contractility
2. Heart rate
3. Preload (stretch)
4. Afterload (squeeze)
5. Blood volume

Question 2

What is the formula for cardiac output? What is the normal CO in an adult?

Answer 2

CO = (HR)(SV)

3-6L/min in adults

Question 3

What is cardiac output?

Answer 3

• amount of blood pumped out of the left ventricle each minute

Question 4

What is preload? (2)

Answer 4

• volume of blood in ventricles at the end of diastole
• aka end diastolic pressure (pre-systole, amount of blood returning to heart)

Question 5

Preload is increased in what instances? (3)

Answer 5

• Hypervolemia
• Regurgitation of cardiac valves
• Heart failure

Question 6

What is afterload?

Answer 6

• Resistance that the left ventricle must overcome to circulate blood

Question 7

What is afterload affected by? (3)

Answer 7

• arteriole BP
• diameter of blood vessels
• pressure in ventricles must be greater than systemic and pulmonic pressures to open aortic + pulmonary valves

Question 8

When would afterload be increased? (2)

Answer 8

• Hypertension
• vasoconstriction

Question 9

An increase in afterload means an increase in _____ _____.

Answer 9

cardiac workload

Question 10

What do electrical properties of the heart regulate? (2)

Answer 10

• HR and rhythm

Question 11

What properties do cardiac muscle cells have? (4)

Answer 11

• excitability
• Conductivity
• Contractility
• Refractoriness

Question 12

What are the important electrolytes for the electrical properties of the heart? (3)

Answer 12

• Na+
• K+
• Ca2+

Question 13

Coronary circulation involves what 3 coronary arteries?

Answer 13

• Right coronary artery (RCA)
• Left anterior descending (LAD)
• Circumflex

Question 14

The right coronary artery supplies blood to what structures? (6)

Answer 14

• Right atrium
• Right ventricle
• part of left ventricle (inferior)
• SA node (50%)
• AV node
• Bundle of His

Question 15

What can occur if the RCA is blocked? (2)

Answer 15

• RV failure
• bradycardia heart block

Question 16

Where does the left anterior descending artery supply blood to? (2)

Answer 16

• Anterior wall of LV
• Heart valves

Question 17

What may occur with blockage of LAD? (3)

Answer 17

• LV failure (main powerhouse perfusion)
• Dysrhythmias (life-threatening)
• Highest mortality rate (most lethal)

Question 18

Where does the circumflex artery supply blood to? (3)

Answer 18

• Left atrium
• Lateral and posterior walls of left ventricle
• SA node (50%)

Question 19

What may occur with blockage of the circumflex artery? (2)

Answer 19

• Left ventricle failure
• Dysrhythmias

Question 20

What is collateral circulation?

Answer 20

• Additional arterial connections found around areas of increasing occlusion

think of it as arteries are highways, and construction develops

Question 21

Why does collateral circulation occur?

Answer 21

• Body’s response to chronic, long-standing ischemia

Question 22

Does collateral circulation always occur with occlusion?

Answer 22

• When arterial occlusion is rapid, there is no time for collateral circulation

Question 23

What are factors that determine collateral circulation?

Answer 23

• Genetic predisposition
• Chronic ischemia

if Hx of hypercholesterolemia, it does not allow collaterals to develop