Chapter 4 Lilly

Question 1

What happens faster, repolarization or depolarization? what is the effect of this on the EKG signalling?

Answer 1

• Repolarization happens slower

- on EKG, we see that repolarization shows as wider and of a lower magnitude

Question 2

why does repolarization occur in the opposite direction of depolarization?

Answer 2

• inner endocardium myocytes have a prolonged action potential so they take longer to repolarize, compared to myocytes at the outer epicardium (shorter action potnetial duration) so they repolarize quicker

Question 3

What are AvF, AvR, and AvL

Answer 3

• Unipolar leads, each one representing a + pole, and their composite sums giving a reference (-)

AvF: Left leg electrode
AvR: Right Arm electrode
AvL: Left arm electrode

Question 4

What are the bipolar leads and what are their components?

Answer 4

I-III

I- Positive electorde is Left arm, negative electrode is rightarm

II - Positive electrode is left leg, negative electrode is right arm

III - positive electrode is left leg, negative electrode is left arm

Question 5

Draw the axial reference system using the six limb leads

Answer 5

See drawing

Question 6

The six standard lim leads examine electrical forces in the _________ plane of the body

Answer 6

frontal

Question 7

P wave represents ______________

Answer 7

depolarization of the atria

Question 8

QRS complex represents ______________

Answer 8

depolarization of the ventricular muscle cells

Question 9

T wave represents _______________

Answer 9

repolarization of the ventricular cells

Question 10

What is the first region of the ventricle to depolarize?

Answer 10

• midportion of the interventricular septum on the left side

Question 11

What is R wave progression?

Answer 11

As you go from V1 to V6, the R wave gets taller because of the leads’ orientation on the body in relation to the heart… going from downward at V1 to tall upward in V6

Question 12

What is the PR interval?

Answer 12

beginning of p to beginning of the qrs complex

Question 13

what is what is QT interval?

Answer 13

beginning of qrs complex to end of t

Question 14

define normal sinus rhythm

define sinus bradycardia

define sinus tachycardia

Answer 14

• 60-100 bpm
• less than 60 bpm
• greater than 100 bpm

Question 15

Define Left axis deviation

Define Right axis deviation

Answer 15

• mean QRS axis more negative than -30 degrees

- mean QRS axis greater than 90 degrees

Question 16

so what’s a normal range of values for mean QRS axis?

Answer 16

• between -30 and 90 degrees

Question 17

What is the effect of hypertrophy on EKG readings?

Answer 17

Hypertrophy is going to increase the electrical activity and increase the magnitude of the wave readings ( directionality depends on the lead and its orientation to the direction of the electric force)

Question 18

Among the most important abnormalities of the ST segments and T waves are those related to ____________ disease

Answer 18

coronary artery disease