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

Fewell - Electrocardiogram - 2021 Flashcards by Elsa Reisenhofer

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

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

How well did you know this?

Not at all

Perfectly

first electrocardiogram done by

Augustus Waller

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

How well did you know this?

Not at all

Perfectly

First practical electrocardiogram was invented by

Willem Einthoven

How well did you know this?

Not at all

Perfectly

Cardiac monitoring systems

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

How well did you know this?

Not at all

Perfectly

3 leads locations and measurements

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

How well did you know this?

Not at all

Perfectly

bipolar leads

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

How well did you know this?

Not at all

Perfectly

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

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

How well did you know this?

Not at all

Perfectly

Lead II

-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)

How well did you know this?

Not at all

Perfectly

what does ECG measure?

>_potentials

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

How well did you know this?

Not at all

Perfectly

ECG Rules

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

How well did you know this?

Not at all

Perfectly

Electrocardiogram - Interpretation

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

TOWARDS causes a positive deflection on ECG trace

- AWAY from causes a negative deflection on the ECG trace

How well did you know this?

Not at all

Perfectly

Electrocardiogram - Interpretation

>wave of repolarization traveling toward a positive electrode

negative deflection in the ECG trace

How well did you know this?

Not at all

Perfectly

120/80 vs 25/8

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

How well did you know this?

Not at all

Perfectly

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

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

How well did you know this?

Not at all

Perfectly

Depolarisation wave

positive complex goes from negative to positive (hill)

How well did you know this?

Not at all

Perfectly

repolarization wave

negative complex goes from positive to negative (valley)

How well did you know this?

Not at all

Perfectly

Vector of waves

magnitude and direction of depolarization/repolarization at that time

P-wave

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

Q-wave

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

R-wave

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.

S-wave

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

T-wave

ventricular muscle repolarizes

Order of electrocardiogram waves

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

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

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

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

it is generated by electrical activity (more | specifically depolarization or activation) of the muscle

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

they are specialized cardiac | muscle cells

Repolarization of the atria is overshadowed by _____

the QRS complex on the | ECG

Arrhythmia condition

A condition in which the heart beats | with an irregular or abnormal rhythm

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

• 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

Sinus Rhythms condition

Any cardiac rhythm where depolarization of the | cardiac muscle begins at the SA node

sinus tachycardia

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

sinus bradycardia

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

2nd degree heart block

- 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

1st degree heart block

very prolonged gap between atria and ventricle signals | -could be determined by examining PQ or PR

complete heart block

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

Premature contraction (atrial)

- 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

premature AV nodal contraction

-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

premature ventricular contraction

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

ectopic focus

an abnormal place or position

atrial fibrillation

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

Ventricular Tachycardia

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

Ventricular Fibrillation

- fatal | - decreased amplitudes