Exam 1/ Lecture 6: Basic Electrocardiography

Question 1

1/30/24

What does the P wave represent, its duration, and which leads is it positive?

Answer 1

* Represents atrial depolarization

• Duration < 0.12 seconds
• Positive: I,II,aVF,V4-V6

Slide 13

Question 2

1/30/24

What does the PR interval represent and its duration?

Answer 2

• Represents AV conduction
• Duration 0.10-0.20

slide 14

Question 3

1/30/24

What does the QRS complex represent, its duration, and the different morphologies?

Answer 3

• Represents ventricular depolarization
• Duration: <0.12 seconds

Morphologies:
* Q physiologic
* R and R prime
* S

Slide 15

Question 4

1/30/24

What does the ST segment represent and when is it significant?

Answer 4

• Early stages of ventricular repolarization
• Elevation/depression > 1mm significant

Slide 16

Question 5

1/30/24

What does the T wave represent and when is it positive?

Answer 5

Ventricular repolarization

Positive in I, II, V3-V6

Slide 17`

Question 6

1/30/24
How does halothane/enflurane cause periop dysrhythmias?

Answer 6

sensitizes myocardium
(slide 37)

Question 7

1/30/24
Which norepi reuptake inhibitors mess with our general anesthetics and cause periop dysrhythmias?

Answer 7

cocaine and ketamine
(slide 37)

Question 8

1/30/24
What dysrhythmia does Sevoflurane cause in infants?

Answer 8

bradycardia

(slide 37)

Question 9

1/30/24

What dysrhythmia does Desflurane cause? and when?

Answer 9

Prolonged QT during induction

(slide 37)

Question 10

1/30/24

What dysrhythmias can Local anesthetics cause?

Answer 10

Severe bradycardia b/c of sympathetic block

• if intravascular, ASYSTOLE!!
• give a lipid rescue!

(slide 37)

Question 11

1/30/24

What is the Most common cause for periop dysrhythmias? (or at least hemodynamic disturbances)

Answer 11

Endotracheal intubation

(slide 38)

Question 12

1/30/24

What Autonomic reflexes during case can cause a periop dysrhythmia?

Answer 12

Vagal stimuli - thru messing w carotid, peritoneum and cervix

(slide 38)

Question 13

1/30/24

What abnormal lyte can cause periop dysrhythmia r/t ventilation?

Answer 13

Hyperkalemia with hypoventilation

(slide 38)

Question 14

1/30/24
What other things specific to surgery cause periop dysrhythmias?

Answer 14

• CVP cannulation
• Surgical manipulation of cardiac structures
• Oculo-cardiac reflex

(slide 39)

Question 15

1/30/24
What 3 things can cause periop dysrhythmias, not surgery specific?

Answer 15

• Hypoxemia
• Cardiac ischemia
• Catecholamine excess

(slide 40)

Question 16

When is atrial repolarization?

Answer 16

during QRS interval

Question 17

What are inherent pacemakers?

Answer 17

SA node

AV node

Ventricular tissue

Question 18

Identify rhythm

Answer 18

Sinus Bradycardia

Question 19

Identify rhythm

Answer 19

Sinus rhythm

Question 20

Answer 20

Sinus tachycardia

Question 21

Lecture 1/30/24

• What are the two cell types within the myocardium?

Answer 21

Pacemaker cells
Contractile cells

Slide 2

Question 22

Lecture 1/30/24

The heart’s ability to generate its spontaneous action potentials without any external stimuli, a phenomenon known as

Answer 22

Automaticity

Slide 2

Question 23

Lecture 1/30/24

What is the name of the specialized cardiac myocytes (muscle cells) within the myocardium that has the capability of generating spontaneous action potentials?

Answer 23

Pacemaker cell

Slide 2

Question 24

Lecture 1/30/24

Where are the pacemaker cells located

Answer 24

SA node,
AV node,
bundle of His,
right and left bundle branches,
Purkinje fibers

Slide 2

Question 25

Lecture 1/30/24

What percentage of the myocardium does the contractile cell make up?

Answer 25

99%

Slide 2

Question 26

Lecture 1/30/24

The contractile cells rely on what system to become depolarized

Answer 26

Conduction system

Slide 2

Question 27

What are the two electrolytes that have a significant effect on the heart if they are nolonger within normal levels?

Answer 27

Potassium
Magnesium

Slide 3

Question 28

Lecture 1/30/24

What type of channel causes cell-to-cell conduction (depolarization) of the myocyte?

Answer 28

Sodium channels

Slide 3

Question 29

Lecture 1/30/24

What happens to the heart after the calcium is released inside the myocyte

Answer 29

Contraction

Slide 3

Question 30

Lecture 1/30/24

What ion outflow causes repolarization

Answer 30

Potassium

Slide 3

Question 31

Lecture 1/30/24

Where is the primary pacemaker located in the heart?

Answer 31

back of the right atrium near the superior vena cava entry

Slide 3

Question 32

Lecture 1/30/24

Which two nerve systems influence the conduction system of the heart?

Answer 32

• sympathetic nervous system to speed up the heart rate by activating cardiac beta receptors.
• Parasympathetic nervous system can facilitate slowing the heart rate down.

Slide 4

Question 33

Lecture 1/30/24

After the SA node generates an action potential, it will travel through the right atrium via what pathway

Answer 33

Internodal pathway

Slide 5

Question 34

Lecture 1/30/24

• What is the muscular bundle composed of parallel muscle strands connecting the left and right atria and serving as the primary electrical connection between the right and left atria

Answer 34

Bachman bundled

Slide 6

Question 35

Lecture 1/30/24

Where is the AV node located?

Answer 35

at the base of the right atrium near the interventricular septum

Slide 6

Question 36

Lecture 1/30/24

• What is the difference between the pacemaker cells in the SA node vs the AV node?

Answer 36

Generate a slower rate (40-60)

Slide 6

Question 37

Lecture 1/30/24

What is an essential factor regarding what happens to the conduction velocity of the action potential in the AV node? How does that affect the atria?

Answer 37

AV node slows down the conduction velocity of the action potential to allow time for the atria to contract before depolarizing the ventricles

Slide 6