Exercise: Pathophysiology and Testing

Question 1

T or F?

During exercise, systole decreases more than diastole (in terms of time)

Answer 1

False.

During exercise, the duration of diastole decreases significantly, whereas systole only decreases a little bit.

Question 2

What is the effect of exercise on Left Ventricular Ejection Fraction?

Answer 2

At rest the ejection fraction is around 60%.

During exercise this can increase by up to 20%. Thus, more blood is ejected, helping to fulfill the increased oxygen demand throughout the body.

Question 3

What is the anticipatory response?

Answer 3

This is when the heart starts beating faster prior to exercise in anticipation of the increased oxygen demand that it’s about to experience.

Question 4

Describe the mechanism whereby the heart rate increases in response to exercise.

Answer 4

At first, the heart rate increases due to parasympathetic withdrawal (up to 100 bpm).

Once it has crossed 100 bpm, the heart rate continues to increase due to sympathetic activity.

Question 5

Other than increased heart rate, how does the heart rate fulfill the demands of increased oxygen during exercise?

Answer 5

The stroke volume increases through:

1) peripheral vasodilation
2) increase in venous return
3) venoconstriction

Question 6

What is the major mechanism for venous return during upright exercise?

How about for dynamic exercise?

Answer 6

Upright exercise: The respiratory pump

Dynamic exercise: the muscle pump

*venoconstriction of vascular smooth muscle occurs in both.

Question 7

Michael Phelp’s Frank-Starling Curve is most likely shifted in which direction?

Answer 7

To the left. This means that at any given EDV, his stroke volume will be greater than the average shmuck.

The opposite is true for someone with LV dysfunction or heart failure.

Question 8

What are the 2 mechanisms whereby contractility and thus stroke volume are increased?

Answer 8

1) Increased sympathetic firing
2) The Frank Starling effect

Question 9

In average people at what point of exercise does stroke volume plateau?

Answer 9

At 40-60% of maximal exercise.

Question 10

T or F?

The EDV is greater in the supine position than in the standing position

Answer 10

True.

For this reason the stoke volume only increases 20-40% in supine exercise.

Question 11

Peyton Manning decides he doesn’t actually want to retire. His doctor advises him to be careful since he’s 40 and should take note that his maximal heart rate will be lower than it was last season. What will be his approximate maximal heart rate?

Answer 11

180 (do 220-age).

Question 12

Average Joe goes from sitting down watching TV to running on the treadmill. What changes should be observed in his cardiac output?

Answer 12

At rest: 5 ml/min (4.5 in females)

On the treadmill: 22 l/min (18 in females)

Normal people: a 4-5 fold increase.

Athletes: a 6-7 fold increase.

Question 13

T or F?

Trained athletes have a same maximal heart rate as untrained people

Answer 13

True.

The cardiac output is much higher in athletes though because their stroke volume is much greater

Question 14

Double question:

What is the average drop in pressure across the entire body?

Where does the greatest drop occur?

Answer 14

Average drop is between 95-115 mmHg (120 aortic pressure, <5 in the veins and RA).

The greatest drop occurs in the arterioles.

Question 15

How is resistance involved in increasing the amount of blood flow during exercise?

Answer 15

There is a decrease in vascular resistance during exercise which allows for increased blood flow.

Question 16

Describe the difference between the response to exercise seen in systolic and diastolic pressure

Answer 16

Systolic: It increases linearly with exercise.

Diastolic: It remains pretty steady, even during exercise.

As a result, the Mean Arterial Pressure and Pulse Pressure (SBP-DBP) both increase during exercise

Question 17

You’re working out hard in the gym. How is your blood flow distribution different right now compared to how it is at rest?

Answer 17

At rest blood flow to skeletal muscle is only about 15%. During exercise, there is vasodilation in skeletal muscle and vasoconstriction in the other organs. As a result, there is a shift and blood flow to skeletal muscle is about 80-85%.

Question 18

T or F?

The percentage of cardiac output that goes to the brain during exercise is less than at rest

Answer 18

True.

The absolute amount of blood that goes to the brain during exercise is greater than what it is at rest. However, since there is so much more cardiac output during exercise, the percentage of blood to the brain compared to other parts of the body is less (3-4% of CO) than at rest (15% of CO).

(I hope that wording makes sense)

Question 19

How does artificially increasing heart rate differ from exercise to increase the heart rate?

Answer 19

You won’t see as much increase in stroke volume if you do it artificially as you would see from someone exercising to increase heart rate.

Question 20

What’s the difference in capillary recruitment in exercise compared to rest?

Answer 20

At rest only 5% are recruited. In exercise, 100% of capillaries are recruited.

Question 21

How do you calculate the arterial oxygen content?

Answer 21

Arterial oxygen content=Hgb*1.34*O₂ saturation

Question 22

What is the Fick equation?

Does cardiac output or oxygen extraction influence the oxygen consumption in exercise more?

Answer 22

Fick Equation: VO₂=CO*a-vO₂

Cardiac output has a greater influence on oxygen consumption in exercise.

*Something key to note: arterial oxygen doesn’t change much during exercise (about 20ml/100ml blood). However, venous oxygen changes by a factor of about 3 (from 15 to 5ml/100 ml blood). This is because more oxygen is being taken up.

Question 23

T or F?

The O₂ levels in the coronary veins are much lower than those of systemic veins at rest.

Answer 23

True.

Systemic veins have about 65% oxygen saturation.

The coronary veins are at 25%. During exercise this drops to 10%.

Question 24

What percentage stenosis of coronary vessels is needed to decrease coronary blood flow at rest?

How about in exercise?

Answer 24

At rest: 90% stenosis

In exercise: 70% stenosis

Question 25

What is the key EKG finding for myocardial ischemia?

Answer 25

ST depression.

Often times you look for this on stress tests.

Question 26

T or F?

RPP is most influenced by heart rate

Answer 26

True.

Question 27

How do you calculate the RPP?

Answer 27

You multiply the SBP by the HR. You can find the values for rest and for exercise. You’ll find a greater range in the values for younger people.

Question 28

What can RPP help to determine?

Answer 28

RPP can determine the extent of coronary disease, the effect of therapy (such as beta blockers), and the effect of exercise.