Fewell - Electrocardiogram - 2021

Question 1

Why can we record electrical activity on the surface of the body

Answer 1

the body is made of water and ions (Na+, K+, Cl- … etc) which conduct electricity
-not recording action potentials but the resulting electrical current

Question 2

first electrocardiogram done by

Answer 2

Augustus Waller

-subject was jimmy the bull dog (put paws in saline and measured current)

Question 3

First practical electrocardiogram was invented by

Answer 3

Willem Einthoven

Question 4

Cardiac monitoring systems

Answer 4

• 3 lead system (can be 5 or 12)
  -looks at the electrical activation of the heart can be picked up using skin electrodes are placed on body
  >one on the right leg to eliminate extraneous info
  >recording ones are on left leg, right arm and left arm

Question 5

3 leads locations and measurements

Answer 5

• lead 1: records activity between right and left arm
• lead 2: right arm and left leg
• lead 3: left arm and left leg

Question 6

bipolar leads

Answer 6

name “bipolar” refers to the fact that one electrode is defined as positive whereas a second electrode is defined as negative

Question 7

what do you get out of an electrocardiogram?
>size of _
>distubrances in_
>extend and localization of \_\_
>effect of _ and _

Answer 7

Anatomical orientation of the heart
• The relative size of the chambers
• Various disturbances in rhythm/conduction
• The extend and localization of ischemia (restricted O2)
• Effect of altered electrolyte concentrations
• Influence of certain drugs

Question 8

Lead II

Answer 8

-right arm is negative and left leg is positive
-good view of what is going on from
the base to the apex of the heart (i.e., up or down)
but a poor view of events moving left to right
(i.e., perpendicular to the Lead II axis)

Question 9

what does ECG measure?

>_potentials

Answer 9

extracellular potentials
-(In the resting, polarized state, no potential difference is measured between the negative and positive electrodes (i.e., isoelectric – flat red line))

Question 10

ECG Rules

Answer 10

1. • A depolarization current wave flowing
     toward the left leg (+ electrode) produces a positive deflection on the ECG
2. A repolarization wave
   flowing toward the left leg (+ electrode) produces a
   negative deflection on the ECG

Question 11

Electrocardiogram - Interpretation

>wave of depolarization traveling TOWARDS vs AWAY from a positive electrode

Answer 11

• TOWARDS causes a positive deflection on ECG trace

- AWAY from causes a negative deflection on the ECG trace

Question 12

Electrocardiogram - Interpretation

>wave of repolarization traveling toward a positive electrode

Answer 12

negative deflection in the ECG trace

Question 13

120/80 vs 25/8

Answer 13

120/8
-systemic circulation
25/8
-pulmonary circulation
(ratios are sastolic over diastolic)

Question 14

why is the venous pressure in the head a negative value?

Answer 14

at recumbent its 5mmHg at the head when upright blood is being pushed up hill than take away 37mmHg when upright (5-37 = -32)

Question 15

Depolarisation wave

Answer 15

positive complex goes from negative to positive (hill)

Question 16

repolarization wave

Answer 16

negative complex goes from positive to negative (valley)

Question 17

Vector of waves

Answer 17

magnitude and direction of depolarization/repolarization at that time

Question 18

P-wave

Answer 18

The electrical activity of the heart originates in the SA node. The impulse then rapidly
spreads through the right atrium to the AV node. It also spreads through the atrial
muscle directly from the right atrium to the left atrium.
It is generated by electrical activation (depolarization) of the muscle of both atria

Question 19

Q-wave

Answer 19

The impulse travels very slowly through the AV node, then very quickly through the
bundle of His, the bundle branches, the Purkinje network, and finally the ventricular
muscle. The first area of the ventricular muscle to be activated is the interventricular septum which activates from left to right

Question 20

R-wave

Answer 20

the left and right ventricular free walls, which form the bulk of the muscle of both
ventricles, are activated; the endocardial surface being activated before the epicardial
surface.

Question 21

S-wave

Answer 21

A few small areas of the ventricles are activated at a rather late stage.

Question 22

T-wave

Answer 22

ventricular muscle repolarizes

Question 23

Order of electrocardiogram waves

Answer 23

P -> Q -> R -> S -> T

Question 24

Why do you NOT see any deflection on the ECG for SA node, AV node and His-Purkinje system undergo depolarization

Answer 24

Because signal is so small it is not transmitted to the surface of the body

Question 25

Why is the P-wave (QRS complex) NOT generated by the contraction of atria (ventricles)?

Answer 25

it is generated by electrical activity (more

specifically depolarization or activation) of the muscle

Question 26

Why does The SA node, AV node, bundle of His, bundle branches and Purkinje
fibre cells are NOT nerve cells.

Answer 26

they are specialized cardiac

muscle cells

Question 27

Repolarization of the atria is overshadowed by _____

Answer 27

the QRS complex on the

ECG

Question 28

Arrhythmia condition

Answer 28

A condition in which the heart beats

with an irregular or abnormal rhythm

Question 29

Arrhythmia common causes
>abnormal _ of the \_\_
>shift of \_\_\_ from \_\_ to \_\_\_
>\_\_ at different points along \_\_
> abnormal \_\_\_
>spontaneous \_\_-

Answer 29

• Abnormal rhythmicity of the pacemaker
• Shift of pacemaker from SA node to another
site in the heart
• Blocks at different points in the spread of
electrical impulse through the heart
• Abnormal pathways of impulse transmission
through the heart
• Spontaneous generation of spurious impulses
in almost any part of the heart

Question 30

Sinus Rhythms condition

Answer 30

Any cardiac rhythm where depolarization of the

cardiac muscle begins at the SA node

Question 31

sinus tachycardia

Answer 31

• QRS complex occurs more often ->increased heart rate
• otherwise complex is normal
• causes: sympathetic stimulation

Question 32

sinus bradycardia

Answer 32

• heart rate is too slow
• cause: parasympathetic stimulation
• still normal QRS complex

Question 33

2nd degree heart block

Answer 33

• first complex is normal but there is a p wave but no QRS complex that follows it
• than a normal QRS complex
• cause: conduction block between the atria & ventricles

Question 34

1st degree heart block

Answer 34

very prolonged gap between atria and ventricle signals

-could be determined by examining PQ or PR

Question 35

complete heart block

Answer 35

atria depolarizes normally and some QRS complexes but no connection between those and P wave

Question 36

Premature contraction (atrial)

Answer 36

• atria is firing an action potential outside of SA node
• produces premature beat arising from an ectopic focus within the atria
• complex is intact but closure together

Question 37

premature AV nodal contraction

Answer 37

-QRS complex is missing P wave
-a premature beat arising from an ectopic focus
within AV node or AV bundle
-smaller irregular amplitude therefore less tissue is depolarizing

Question 38

premature ventricular contraction

Answer 38

• a premature beat arising from an ectopic focus within the ventricle
• larger irregular amplitude (QRS without preceding P wave)

Question 39

ectopic focus

Answer 39

an abnormal place or position

Question 40

atrial fibrillation

Answer 40

-random pattern of electrical pattern uncoordinated contraction
-decreases heart efficiency
>causes: blood clots and stroke

Question 41

Ventricular Tachycardia

Answer 41

• QRS complex is prolonged and high voltage
• smaller amplitudes everywhere
• very random ventricular contraction

Question 42

Ventricular Fibrillation

Answer 42

• fatal

- decreased amplitudes