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Cardiology Flashcards

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0
Q

Depolarization

A

The discharge of energy that accompanies the transfer of electrical charges across the cell membrane.

Differs from contraction in that depolarization is an electrical phenomenon, whereas contraction is mechanical and is expected to follow depolarization.

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1
Q

Polarization

A

When the electrical charges are balanced and ready for discharge.

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2
Q

Repolarization

A

The return of electrical charges to their original state of readiness.

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3
Q

Arrhythmias

A

Graphic representations of electrical activity.

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4
Q

Two types of heart cells:

A
  1. Electrical cells, which stimulate (initiate and conduct impules).
  2. Mechanical cells, which contract in response to stimulation.

Electrical activity precedes mechanical activity.
Electrical activity can occur without mechanical response (pulse).

If the electrical impulse stimulates the mechanical cells to contract, the heart is expected to contract and pump blood, thus producing a pulse.

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5
Q

Electrical flow in the normal heart:

A

Originates in the SA node, then travels via the intraatrial and intranodal pathways to the AV node , then through the Bundle of His to the Left and Right Bundle Branches, and finally to the Purkinje Fibers, where mechanical cells are stimulated.

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6
Q

Inherent rate of the SA Node

A

60-100 BPM

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7
Q

Inherent rate of the AV Junction

A

40-60 BPM

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8
Q

Inherent rate of the Ventricles

A

20-40 BPM

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9
Q

Sinoatrial Node (SA Node)

A

Impulse-generating (pacemaker) tissue located in the right atrium of the heart. Generator of normal sinus rhythm. The SA Node initiates impulses at the fastest rates and is the NORMAL pacemaker of the heart.

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10
Q

Irritability

A

When a site speeds up and takes over as the pacemaker.

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11
Q

Rule regarding the pacemaker function of the heart:

A

The site that initiates impulses at the fastest rate will usually become the pacemaker.

eg.: if the SA node failed as pacemaker, or if its rate dropped below the normal range, the AV Junction would probably take over as pacemaker. This is known as ESCAPE

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12
Q

Escape

A

When the normal pacemaker of the heart slows down or fails and a lower site assumes pacemaking responsibility.

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13
Q

Sympathetic response causes:

A

Increased heart rate (chronotropic)
Increased AV conduction/Increased irritability (dromotropic)
Increased contractility (inotropic)

The sympathetic branch influences both the atria (SA node, the intraatrial and intranodal pathways, and AV junction) and ventricles.

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14
Q

Parasympathetic response causes:

A

Decreased heart rate
Decreased AV conduction
Decreased irritability

The parasympathetic branch influences only the atria.

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15
Q

Areas of conduction system in the order in which the impulses travel through the heart:

A
  1. SA Node
  2. Intraatrial and Internodal Pathways
  3. AV Node
  4. Bundle of His
  5. Left and Right Bundle Branches
  6. Purkinje Fibers
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16
Q

Normal pacemaking site of the heart, and why?

A

The SA Node. It has the fastest inherent rate at 60-100/min.

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17
Q

The process responsible for a site speeding up and overriding a higher site, thus taking over as pacemaker?

A

Irritability

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18
Q

Mechanism in play if a lower site takes over responsibility for the pacemaking function following a failure of a higher site?

A

Escape

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19
Q

The discharge of electrical energy that accompanies the transfer of electrical charges across the cell membrane?

A

Depolarization

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20
Q

The return of the electrical charges to their original state of readiness?

A

Repolarization

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21
Q

Nervous system that controls the activities of the heart?

A

Autonomic

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22
Q

What part of the heart does the sympathetic branch innervate?

A

The atria and ventricles.

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23
Q

What part of the heart does the parasympathetic branch innervate?

A

Only the atria

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24
What happens if the sympathetic branch of the heart is blocked, or vice versa?
If the sympathetic branch of the heart is blocked, the influence of the parasympathetic branch will control the heart. If the parasympathetic branch of the heart is blocked, the influence of the sympathetic branch will control the heart.
25
Which rhythms originate from the SA Node?
Normal Sinus Rhythm Sinus Bradycardia Sinus Tachycardia Sinus Arrhythmia
26
Rules for Normal Sinus Rhythm (NSR)?
Regularity: Regular Rate: 60-100 BPM P Wave: Uniform, upright; one P wave in front of every QRS complex PRI: measures b/n 0.12-0.20 second and is constant across the strip QRS: measures less than 0.12 second
27
Rules for Sinus Bradycardia?
Regularity: Regular Rate: less than 60 BPM P Wave: uniform, upright; one P wave in front of every QRS complex PRI: measures b/n 0.12-0.20 second and constant across the strip QRS: measures less than 0.12 second
28
Rules for Sinus Tachycardia?
Regularity: Regular Rate: Greater than 100 BPM (usually 100-160 BPM) P Wave: uniform, upright; one P wave in front of every QRS complex PRI: measures b/n 0.12-0.20 second and constant across the strip QRS: measures less than 0.12 second
29
Rules for Sinus Arrhythmia?
Regularity: Irregular Rate: 60-100 BPM (usually) P Wave: uniform, upright; one P wave in front of every QRS complex PRI: measures b/n 0.12-0.20 second and is constant across the strip QRS: measures less than 0.12 second
30
Sinus Rhythm w/ a wide QRS?
Rhythm has been determined to have originated in the sinus node, but has a QRS measurement greater than 0.12 second.
31
Why do sinus rhythms have upright P waves?
Because the impulse originates in the SA node travels downward through the atria to the ventricle. In Lead II, the positive electrode is placed below the apex, thus the major electrical flow is toward the positive electrode in Lead II, creating an upright wave form.
32
Rate of NSR?
60-100 BPM
33
PRI for NSR?
0.12-0.20 second and constant across the strip
34
QRS of NSR?
Less than 0.12 second
35
What will the P wave be like for sinus rhythms?
Uniform, upright; one P wave in front of every QRS complex
36
Rate for sinus bradycardia?
Less than 60 BPM
37
Rate for Sinus Tachycardia?
Greater than 100 BPM (usually 100-160 BPM)
38
Rhythm/Regularity of Sinus Arrhythmia?
Irregular. The rate increases with each respiratory inspiration and decreases with each expiration.
39
PR Interval (PRI)
-Includes the P wave and the PR segment. -Represents both atrial depolarization and delay in the AV node. -Measurement: beginning of the P wave to the beginning of the QRS complex. -Normally between 0.12-0.20 second
40
Lead
Single view of the heart, often produced by a combination of information from several electrodes.
41
Electrode
Devices applied to the skin to detect electrical activity and convey it to a machine for display.
42
What causes an upright wave?
If electricity flows towards a positive electrode, the patterns produced on graph paper will be upright.
43
What causes an inverted wave?
If electrical flow is toward the negative electrode, the patterns will be inverted.
44
Why is electrode placement standardized?
To avoid confusion in EKG interpretation.
45
Isoelectric line
A straight line made on the EKG when no electrical current is flowing (flatline).
46
What do the vertical lines on the graph paper measure? Horizontal?
Vertical lines measure time. Horizontal lines measure voltage.
47
Time frame of small squares? Large squares?
Small squares = 0.04 second Large squares = 0.20 second
48
What part of the cardiac cycle does a P wave represent?
The P wave represents atrial depolarization. It is measured from the first deflection on the cardiac cycle until the deflection returns to the isoelectric line.
49
Which part of the cardiac cycle does the PR segment represent?
The PR segment represents the delay in the AV node. It is a short period of electrical inactivity. The tissues of the node do not conduct impulses as fast as other cardiac electrical tissues. The wave of depolarization takes a longer time to get through the AV node than it would in other parts of the heart. This is necessary to allow time for the for atrial contraction and complete filling of the ventricles.
50
QRS Complex
- Represents ventricular depolarization - Measured from the beginning of the Q wave to the end of the S wave. - Normally less than 0.12 second
51
External factors capable of producing artifact on the EKG tracing?
Muscle Tremors, shivering Patient movement Loose electrodes 60-cycle electrical current
52
Electrical refractory
When a cell has not yet repolarized and thus cannot accept and respond to another stimulus.
53
Absolute refractory period
The absolute refractory period occurs when the cells cannot respond to any stimulus at all. The absolute refractory period encompasses the QRS and the first part of the T wave.
54
Relative refractory period
The relative refractory period occurs when some of the cells are capable of responding if the stimulus is strong enough. If an impulse falls during the relative refractory period, the heart might be depolarized, but in an abnormal way. The relative refractory period is the downslope of the T wave.
55
Electrode positionings for Lead II
Negative electrode below right clavicle. Positive electrode left ankle. Ground electrode below the left clavicle.
56
Pathway of blood through the heart, starting at the superior and inferior vena cava:
Blood from the body flows to the superior and inferior vena cava, then to the right atrium, through the tricuspid valve to the right ventricle, through the pulmonic valve to the pulmonary artery, to the lungs/bronchioles/alveoli/capillary beds. The blood picks up oxygen in the lungs, and then flows from the lungs: to the pulmonary veins to the left atrium, through the bicuspid/mitral valve to the left ventricle, through the aortic valve to the aorta to the aortic arch to the body
57
What does the T wave represent
Ventricular repolarization
58
What causes atrial arrhythmias?
Atrial arrhythmias occur when an ectopicv focus in the atria ssumes responsibility for pacing the heart, either by irritability or escape.
59
Any focus that originates outside of the SA node:
Ectopic focus
60
Because the atrial focus is outside of the SA node, an impulse coming from it would cause an unusual depolarization wave, thus causing the P wave to have an unusual configuration. Atrial P waves appear:
Flattened, notched, peaked, or diphasic.
61
When the pacemaker shifts between the SA node and the Atria, causing each P wave to differ slightly from those around it:
Wandering Pacemaker
62
``` Rules for Wandering Pacemaker: Rhythm Rate P wave PRI QRS ```
``` Rhythm: slightly irregular Rate: usually normal, between 60-100 bpm P wave: morphology changes from beat to beat PRI: less than 0.20; may vary QRS: less than 0.12 ```
63
Single beats that originate in the atria and come early in the cardiac cycle?
Premature Atrial Complexes (PAC's)
64
Ectopic beats that come early in the cardiac cycle are caused by _____________; ectopic beats that come later than expected in the cardiac cycle are caused by ______________.
Irritability; escape mechanism
65
When confronted with ectopics, you must identify both the ___________ and the ______________.
ectopic; underlying rhythm
66
A rhythm with ectopic beats will be _____________, even if the underlying rhythm is characteristically _____________.
irregular; regular
67
Ectopics interrupt the ___________ of the underlying rhythm.
regularity
68
``` Rules for Premature Atrial Complexes: Rhythm Rate P Wave PRI QRS ```
Rhythm: depends on the underlying rhythm; usually regular except for the PAC Rate: usually normal; depends on the underlying rhtym P Wave: P wave of the PAC differs from the regular beat, can be flattened or notched; may be lost in the preceding T wave PRI: 0.12 - 0.20; can be greater than 0.20 QRS: less than 0.12
69
Caused when a single focus in the atria fires very rapidly and overrides the SA node?
Atrial Tachycardia
70
``` Rules for Atrial Tach Rhythm Rate P Wave PRI QRS ```
``` Rhythm: Regular Rate: 150 - 250 bpm P Wave: Atrial P wave; can be lost in the preceding T wave PRI: 0.12 - 0.20 QRS: less than 0.12 ```
71
Atrial arrhythmia that occurs when ectopic foci in the atria becomes so irritable that they fire faster than a rate of 250 bpm:
Atrial Flutter
72
Flutter waves, or F waves have a ____________ appearance.
Sawtooth
73
``` Rules for Atrial Flutter Rhythm Rate P Wave PRI QRS ```
Rhythm: atrial rhythm is regular; ventricular rhythm is regular, but can be irregular if there is a variable block Rate: atrial rate 250 - 350 bpm, ventricular rate varies P Wave: characteristic sawtooth pattern (F waves) PRI: unable to detemrine QRS: less than 0.12
74
``` Rules for Atrial Fibrillation Rhythm Rate P Wave PRI QRS ```
Rhythm: grossly irregular Rate: Atrial rate <350 bpm, ventricular rate varies greatly; 100 bpm or less is considered "controlled," <100 is considered "uncontrolled."
75
In controlled atrial fib, the ventricular rate is _____________. In uncontrolled atrial fib, the ventricular rate is _____________.
100 or less; 100 or more

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