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ECG > Chapter 1 Basic Principle, Rapid Interpretation of EKG's > Flashcards

Chapter 1 Basic Principle, Rapid Interpretation of EKG's Flashcards

1
Q

Scientific establishment of pumping of heart and electrical phenomena

A
  • Kollicker and Mueller (1855)
  • lay motor nerve to frogs leg over isolated beating heart
  • leg would kick with each heartbeat
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2
Q

Capillary electrometer

A
  • created by Ludwig and Waller (1880’s)
  • hearts rhythmic electrical stimuli can be monitored from a person’s skin
  • capillary tube in a electric field that can detect faint electrical activity - find that fluid level in capillary tube moved with the rhythm of the subjects heart beat
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3
Q

Invention of the 1st EKG machine

A
  • Einthoven (1901)
  • attaches two electrodes to a person skin
  • ends of electrodes connect to ends of a silver wire passing through poles of a magnet
  • projects a light bean through holes in the magnets poles across the silver wire which twitches to the rhythm of the subjects heartbeat
  • creates shadow of distinct waves in repeating ycles
  • names waves P, QRS, T
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4
Q

Function of the EKG

A

Records the electrical activity of contraction of the heart muscle

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5
Q

Charge Myocardial cells in resting state

A
  • polarized

- interior of every cell is negatively charged (negative interior and positively charged outside surface)

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6
Q

Charge myocardial cells during contraction

A
  • depolarized

- interior become positive

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7
Q

Depolarization of the myocardium

A
  • an advancing wave of positive charges within the heart’s myocytes
  • due to movement of Na+ through fast-moving Na+ chanels
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8
Q

Upward deflection on EKG - meaning

A

Represents a depolarization wave moving toward a positive electrode

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9
Q

Hearts dominant pacemaker

A

SA node

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10
Q

Sinus rhythm

A

Normal pacing activity of SA node

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11
Q

Automaticity

A

The generation of pacemaking stimuli

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12
Q

Automaticity foci

A

Other focal areas of the heart that have automaticity

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13
Q

Atrial depolarization (and contraction)

A

Spreading wave of positive charges within the atrial myocardial cells

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14
Q

P wave

A

Upward deflection produced by depolarization of atria on EKG

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15
Q

Function of atrio-ventricular valves - electrical conduction

A

Insulate the atria from the ventricles (making AV node the only conducting path between the atria and the ventricles)

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16
Q

Timelapse at AV node

A

When wave of atrial depolarization enters the AV node depolarization slows producing a brief pause and allowing time for the blood in the atria to enter the ventricles (due to slow conducting Ca2+ ions)

Allows time for the blood to pass into the ventricles (takes time for blood to flow through the valves into the ventricles after the atria contract)

Produces flat baseline after each P wave

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17
Q

Reason why depolarization conducts slowly through the AV node

A

Due to current being carried by slow-moving Ca2+ ions

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18
Q

Ventricular conduction system

A

1) Bundle of His (penetrates the AV valves)
2) Bundle bifurcates in the interventricular septum into right and left bundle branches
3) Terminate in network of tiny filaments of purkinje fibers

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19
Q

Purkinje fibers

A
  • rapidly conducting fibers that form the right and left bundle branches and the bundle of His
  • use fast-moving Na+ ions for the conduction of depolaization
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20
Q

QRS complex

A

Corresponds to the depolarization of the ventricular myocardium on EKG

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21
Q

Terminal filaments of the Purkinje fibers - location + what this means for direction depolarization of ventricles

A

Spread out just beneath the endocardium that lines both ventricular cavities
Ventricles epolarize from the lining towards the outside surface (epicardium)

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22
Q

Relationship QRS to ventricular contraction

A

QRS complex represents only the beginning of ventricular contraction (a recording of ventricular depolarization which causes ventricular contraction)
Physical event of ventricular contraction lasts longer than the QRS complex

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23
Q

Q wave

A

The first downward wave of the QRS complex

Often absent

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24
Q

R wave

A

The first upward deflection of the QRS complex

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25
Q

S wave

A

Any downward wave preceded by an upward wave

26
Q

QS wave

A

When there is only a downward deflection (no R wave)

Can’t tell whether the deflection is a Q or S wave therefore is called a QS wave

27
Q

ST segment

A

The horizontal segment of baseline that follows the QRS complex
Normally should be level with other ares of baseline (if it is elevated or depressed beyond the normal baseline level is sign of problem!)

28
Q

ST segment - what does represent

A

The plateau phase of ventricular repolarization (when K+ exit and Ca2+ entry are balanced)
Ventricular repolarization is rather minimal during this segment

29
Q

What does the T wave represent

A

Represents the rapid phase of ventricular repolarization

Accomplished by K+ leading the myocytes

30
Q

Stages of EKG that ventricular systole corresponds to

A

Spans depolarization and repolarization of ventricles so from QRS to end of T wave
I.e. the QT interval

31
Q

Why QT interval is a good indicator of repolarization

A

Snce repolarization comprises the most of the QT interval

32
Q

Long QT interval syndrome

A
  • hereditary syndromes

- make people more vulnerable to rapid ventricular rhythms (why it is important to detect a prolonged QT interval)

33
Q

How does the QT interval vary

A

Varies with heart rate - with rapid heart rate both depolarization and repolarization occur faster

Therefore precise QT interval measurements are corrected for rate (QTc values)

34
Q

What is considered a normal QT interval

A

-when it is less than half of the R-R interval at normal rates

35
Q

Smallest divisions on EKG strip

A

-one millimeter by one millimeter

36
Q

Large boxes

A
  • denoted by heavy black lines on each side

- each side is 5 mm long (5 small boxes)

37
Q

Measure of voltage on EKG

A

The height and depth of a wave measured verticaly frm basline in mm
-vertical amplitude is a measure of voltage

38
Q

Amplitude of a wave

A

The magnitude (in millimeters) of the deflection and is a measure of voltage

39
Q

Measuring elevation/depression of segments of baseline

A

Measured vertically in mm (just like measure waves)

40
Q

Conversion mm to mV

A

10 mm verticaly represents one mV

41
Q

Amount of time represented by the distance between two heavy black lines (5 small boxes)

A

0.2 of a second

42
Q

Amount of time represented by each small division

A

0.04 of a second

43
Q

How to determine the duration of any wave

A

Measure along its horizontal axis

44
Q

Leads in a standard EKG

A
  • 12 separate leads

- six limb leads, six chest leads

45
Q

Placement of limb leads

A

-right arm
-left arm
-left leg
(Placement of electrodes, two electrodes are used to record a lead, a different pair for each lead)

46
Q

Bipolar limb leads

A
  • uses two electrodes: one positive, one negative
  • include lead I-III
  • this configuration is also called Einthoven’s triangle
47
Q

Lead I

A

Positive electrode on left arm

Negative electrode right arm

48
Q

Lead II

A

Positive electrode left leg

Negative electrode right arm

49
Q

Lead III

A

Positive electrode left leg

Negative electrode left arm

50
Q

Bipolar limb leads moved to intersect at a centre point

A

There is a center of the triangle formed by the arrangement of the bipolar limb leads
Can push limb leads so that they intersect this center point but still remain at same angles relative to each other (still yielding the same info)

51
Q

AVF lead

A

Uses left foot electrode as positive

Remaining two electrodes are channeled into a common ground that has a negative charge

52
Q

AVR lead

A

Right arm electrode is positive, remaining two electrodes negative

53
Q

AVL lead

A

The left arm is positive and the remaining two are negative

54
Q

Augmented limb (unipolar) organization

A
  • intersect at different angles than those produced by bipolar limb leads (split the angled formed by the bipolar limb leads)
  • intersect at 60 degree angles
55
Q

Frontal plane

A

Arrangement of six limb leads; the bipolar leads superimposed over the augmented leads

56
Q

Importance of all six limb leads

A

All record a different angle (viewpoint) to provide a different view of the same cardiac activity

57
Q

Why do the waves look different in each lead

A

Recording the same cardiac activity in each lead but looks different because the heart’s electrical activity is recorded from different angles for each lead

58
Q

Conventional grouping of limb leads

A

Latera leads and inferior leads
To determine whether the depolarization is moving toward or away from the patients left side and whether it is directed inferiorly toward or away from the left foot

59
Q

Lateral leads

A

lead I, AVL

60
Q

Inferior leads

A

Lead II, III and AVF

61
Q

Position of chest leads

A

Cover the heart in its anatomical position within the chest
Each lead is oriented through the AV node and projects through the patients back
In the horizontal plane (cut body into top and bottom halves)

ECG (6 decks)

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