EKG BASICS

Question 1

definition: cardiac cells; electrically polarized at rest

Answer 1

myocytes

Question 2

what charge do inside of myocytes have?

Answer 2

electro-negatively charged compared to outside

Question 3

how is polarity maintained in myocytes?

Answer 3

sodium-potassium membrane pumps

Question 4

how is relative electro-positive extracellular state maintained?

Answer 4

3 Na pumped out for every 2 K pumped in (requires ATP)

Question 5

definition: electrical power source of the heart; depolarize spontaneously

Answer 5

pacemaker cells

Question 6

definition: hard-wiring of the heart

Answer 6

electrical conducting cells

Question 7

definition: the contractile machinery of the heart

Answer 7

myocardial cells

Question 8

how is rate of depolarization of pacemaker cells determined?

Answer 8

determined by the innate electrical characteristics of that cell and the external neurohormonal input

Question 9

what is the normal intrinsic pacing rate of the SA node?

Answer 9

60-100bpm, but can vary with ANS stimulation

Question 10

definition: all heart cells possess ability to behave as a pacemaker. suppressed unless SA node fails

Answer 10

automaticity

Question 11

what is the normal intrinsic pacing rate of the atrial foci?

Answer 11

60-75bpm

Question 12

what is the normal intrinsic pacing rate of the junctional foci (AV node)?

Answer 12

40-60bpm

Question 13

what is the normal intrinsic pacing rate of the ventricular foci?

Answer 13

25-40bpm

Question 14

definition: ventricular conducting cells

Answer 14

purkinje fibers

Question 15

definition: atrial conducting pathways that travel through the intra-atrial septum; allows for rapid activation of the LA from the RA

Answer 15

bachman’s bundle

Question 16

definition: when a wave of depolarization reaches a myocardial cell, calcium is released within the cell allowing actin and myosin to interact, causing the cell to contract

Answer 16

excitation-contraction coupling

Question 17

how is the duration of a wave measured?

Answer 17

fractions of a second

Question 18

how is the amplitude of a wave measured?

Answer 18

millivolts

Question 19

definition: shape and appearance of a wave

Answer 19

configuration

Question 20

horizontal axis of EKG measures what?

Answer 20

time

Question 21

vertical axis of EKG measures what?

Answer 21

voltage

Question 22

small/large square horizontal distance =

Answer 22

0.04/0.2sec

Question 23

small/large square vertical distance =

Answer 23

0.1/0.5mV

Question 24

the P wave is a recording of what?

Answer 24

atrial depolarization

Question 25

define what the 1st and 2nd part of the P wave represent

Answer 25

1st part: RA depolarization | 2nd part: LA depolarization

Question 26

definition: AV node delays conduction from the atria to the ventricles to allow atria to finish contracting/emptying their volume completely into the ventricles before the ventricles contract

Answer 26

AV nodal delay

Question 27

name the three components of ventricular conduction

Answer 27

1. bundle of his 2. bundle branches 3. terminal purkinje fibers

Question 28

definition: marks the beginning of ventricular depolarization and contraction

Answer 28

QRS complex

Question 29

definition: restoration of electronegative state so that myocardial cells can be restimulated

Answer 29

repolarization

Question 30

represents the wave of ventricular repolarization

Answer 30

t wave

Question 31

why do we not see the wave of atrial repolarization?

Answer 31

it is obscured by the QRS complex

Question 32

definition: measures time from start of atrial depolarization to start of ventricular depolarization

Answer 32

PR interval

Question 33

definition: measures time from end of ventricular depolarization to the start of ventricular repolarization

Answer 33

ST segment

Question 34

definition: measures time from beginning of ventricular depolarization to the end of ventricular repolarization

Answer 34

QT interval

Question 35

definition: a wave of depolarization towards a positive electrode

Answer 35

positive deflection

Question 36

definition: a wave of depolarization away from a positive electrode

Answer 36

negative deflection

Question 37

definition: a depolarizing wave moving perpendicular to a positive electrode

Answer 37

biphasic wave

Question 38

a wave of repolarization moving toward a positive electrode gives a ________ ___________ and vice versa

Answer 38

negative deflection

Question 39

a 12-lead EKG includes what leads?

Answer 39

six limb leads (2 electrodes on arms, 2 on legs = 3 standard leads + 3 augmented leads six precordial leads (six electrodes placed across the chest)

Question 40

position of V1 lead

Answer 40

4th intercostal (right)

Question 41

position of v2 lead

Answer 41

4th intercostal (left)

Question 42

position of v3 lead

Answer 42

between v2 and v4

Question 43

position of v4 lead

Answer 43

5th intercostal space midclavicular

Question 44

position of v5 lead

Answer 44

5th intercostal space anterior axillary line

Question 45

position of v6 lead

Answer 45

5th intercostal space midaxillary line

Question 46

describe where the positive and negative terminals of the precordial leads are

Answer 46

all electrodes are + | central - terminal is created by connecting all 3 extremity leads

Question 47

which leads make up the anterior view of the heart?

Answer 47

v2, v3, v4

Question 48

which leads make up the left lateral view of the heart?

Answer 48

I, aVL, v5, v6

Question 49

which leads make up the inferior view of the heart?

Answer 49

II, III, aVF

Question 50

which leads make up the right ventricular view of the heart?

Answer 50

aVR, v1

Question 51

how long does the PR interval last on EKG?

Answer 51

0.12-0.2sec

Question 52

what is the normal amplitude of the Q wave?

Answer 52

-0.1mV

Question 53

a large negative deflection of the Q wave in leads II, III, and aVF denote what pathology?

Answer 53

inferior MI

Question 54

the R wave is smallest/largest in which leads?

Answer 54

v1/v5

Question 55

how long does a normal QRS complex last?

Answer 55

0.06-0.1sec

Question 56

the QT interval composes ___% of the normal cardiac cycle (R-R)

Answer 56

40%