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Physiology > Exam 2 – Cardio Ch 13 > Flashcards

Exam 2 – Cardio Ch 13 Flashcards

(78 cards)

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1
Q

What are causes of cardiac arrhythmias?

A

Abnormal rhythmicity of the pacemaker
Shift of pacemaker from sinus node
Blocks at different points in the transmission of the cardiac impulses
Abnormal pathways of transmission in the heart
Spontaneous generation of abnormal impulses from any part of the heart

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2
Q

What are normal causes of sinus arrhythmia?

A

Increase in heart rate during inhalation
Decrease in heat rate during exhalation
Autonomic input associated with respiration

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3
Q

What are abnormal sinus rhythms?

A

Tachycardia

Bradycardia

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4
Q

Define tachycardia

A

Fast heart rate is greater than normal range

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5
Q

What causes tachycardia?

A

Increased body temperature
Sympathetic stimulation (blood loss, reflex stimulation of the heart)
Toxic conditions

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6
Q

How does increased body temperature cause tachycardia?

A

Due to increased rate of metabolism of sinus node which in turn directly increase its excitability and rate of rhythm

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7
Q

Define bradycardia

A

Slow heart rate lower than normal range

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8
Q

Why is bradycardia present in some athletes?

A

They have a large stroke volume

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9
Q

What can cause bradycardia?

A

Vagal stimulation

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10
Q

What is carotid sinus syndrome?

A

Especially sensitive syndrome that easily triggers vagal stimulation

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11
Q

Define sinoatrial block

A

In rare instances impulses from SA node are blocked before it enters atrial muscle

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12
Q

What does sinoatrial block cause cessation of?

A

P wave

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13
Q

What is the new pacemaker in sinoatrial block?

A

Region of heart with the next fastest discharge rate, usually AV node

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14
Q

Due to cessation of P waves in sinoatrial block, what is occasionally seen?

A

Atrial standstill

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15
Q

Define atrioventricular block

A

Impulses through AV node and AV bundle are slowed down or blocked

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16
Q

What causes atrioventricular block?

A

Ischemia
Compression
AV nodal/AV bundle inflammation
Excessive vagal stimulation

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17
Q

What is the AV bundle also known as?

A

Bundle of HIS

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18
Q

Describe incomplete heart block first degree block

A

Long space between P wave and QRS

Prolonged PR interval

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19
Q

What can the PR interval not be longer than in a first degree block?

A

RR interval

Cannot be longer than space between two beats

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20
Q

Why is a first degree block considered incomplete?

A

Delay of conduction from atria to ventricles but not actual blockage of conduction

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21
Q

Describe second degree incomplete block

A

PR interval increased

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22
Q

What is Mobitz Type ! or Wenkebach second degree block?

A

PR gets longer with each beat until a beat is dropped

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23
Q

What is Mobitz Type 2 second degree block?

A

Some impulses pass through AV node and some do not thus causing “dropped beats”
Fixed number of nonconducted P waves for every QRS complex

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24
Q

What happens to atria speed in second degree incomplete block?

A

It beats faster than ventricles

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25
What species tends to have mild second degree block at rest?
Horses
26
Describe third degree complete block
Total block through AV node or AV bundle
27
How are the P waves in a third degree complete block?
Completely dissociated from QRST complexes | AV dissociation
28
What happens to ventricles in third degree complete block?
Ventricles escape and AV nodal rhythm ensues Spontaneously establish their own signal, usually originating in AV node or AV bundle
29
Is there a relation between rhythm of P waves and QRST complex in third degree complete block?
No because ventricles escape control from atria and beats at its own natural rate
30
Describe Stokes-Adams syndrome
Fainting associated with complete AV block
31
How is the complete AV block in stokes-adams syndrome?
It comes and goes
32
What happens to ventricles in stokes-adams syndrome?
Ventricles stop contracting for 5-30 seconds because of overdrive suppression meaning they are used to atrial drive
33
Why does the patient faint from stokes-adams syndrome?
Because of poor cerebral blood flow
34
What does the ventricle escape in stokes-adams syndrome?
AV nodal or AV bundle rhythm (15-40 beats/min)
35
What will correct stoke-adams syndrome?
Pacemaker
36
What happens to the impulse in incomplete intraventricular block (electrical alternans)?
Sometimes blocked and sometimes not in peripheral portions of purkinje system resulting in abnormal QRS waves
37
What can cause incomplete intraventricular block?
Ischemia Myocarditis Digitalis toxicity
38
What is incomplete intraventricular block associated with?
Pleural and/or pericardial effusions in animals
39
What happens to the PR interval in premature atrial contractions?
Shortened if ectopic foci originating the beat are near AV node
40
Where does the impulse travel in premature atrial contractions?
Through AV node and back toward sinus node causing discharge of the sinus node Next sinus discharge will thus be late
41
How does an early contraction affect the heart?
It doesn't allow the heart to fill with blood causing a low stroke volume and a weak radial pulse
42
How does Av nodal or AV bundle premature contractions affect the P waves?
Early and inverted Missing Late and inverted
43
When the P wave is early and inverted, where is the premature contraction in the AV junction?
High AV junction
44
When the P wave is missing, where is the premature contraction in AV junction?
Mid AV junction
45
When the P wave is late and inverted, where is the premature contraction in AV junction?
Low AV junction
46
Where does the impulse travel in a AV junctional premature contractions?
Backward into atria
47
What happens to the QRS in premature ventricular contractions?
QRS is prolonged because impulse is conducted through muscle which has slow conduction
48
What happens to the QRS voltage in premature ventricular contractions?
High because one side depolarizes ahead of the other
49
What happens to the T wave in premature ventricular contractions?
Inverted because slow conduction causes the area to first depolarize to also repolarize first (opposite of normal)
50
What causes T wave premature ventricular contractions?
Cigarettes Coffee Lack of sleep
51
define paroxysmal
A series of rapid heart beats suddenly start and then suddenly stop
52
What can stop atrial paroxysmal tachycardia?
Vagal reflex | Quinidine or procainmide or lidocaine
53
What happens to the P wave in atrial paroxysmal tachycardia?
Inverted if origin is near AV node
54
How does atrial paroxysmal tachycardia?
Occurs by re-entrant pathways
55
What autonomic discharge occurs in atrial paroxysmal tachycardia?
High sympathetic discharge
56
What is an atrial flutter?
Single large impulses wave travels around area in one direction
57
What is the atrial contraction speed in an atrial flutter?
200-350 beats/min
58
When will the AV node not pass signal in atrial flutter?
Not pass signal until 0.35 seconds elapses after previous signal Therefore, atria may beat 2 or 3 times as rapidly as ventricle
59
What does atrial fibrillation most often occur without?
Ventricular fibrillation
60
What is the most frequent cause of atrial fibrillation?
Atrial enlargement due to AV valve dysfunction | This causes a long pathway of conduction which is favorable for circus movements
61
What happens to the efficiency of ventricular pumping because of atrial fibrillation?
Decreased 20-30 percent
62
Why does an irregular, fast heart rate occur in atrial fibrillation?
Because of irregular arrival of cardiac impulses at AV node
63
What does atrial fibrillation sound like?
Tennis shoes in a dryer
64
When does ventricular paroxysmal tachycardia occur?
Usually does not occur unless there has been ischemic damage
65
What can fix the problem of ventricular paroxysmal tachycardia?
Quinidine increases refractory period of cardiac muscle
66
When do circus movements occur in ventricular fibrillation?
If pathway is long If conduction velocity is decreased If refractory period is shortened
67
What causes a long pathway in ventricular fibrillation?
Dilated heart
68
What causes decreased conduction velocity in ventricular fibrillation?
Blockade of purkinje system Ischemia of muscle High K+ levels
69
What causes shortened refractory period in ventricular fibrillation?
Epinephrine release
70
What is ventricular fibrillation compared to?
Bag of worms
71
Why is ventricular fibrillation considered a bag of worms?
Some parts of ventricle contract while others relax thus little blood flows out of heart
72
What is ventricular fibrillation caused by?
Electrical shock or cardiac ischemia
73
What is ventricular defibrillation?
1000 volts direct current is applied for a few thousandths of a second
74
Which parts of the heart become refractory during ventricular defibrillation?
All parts of the heart become refractory and remain quiescent for 3-5 seconds until new pacemaker is established
75
What happens to the heart if used later than one minute after fibrillation?
The heart is too weak to defibrillate and may have to be hand-pumped/CPR
76
When does cardiac arrest usually occur?
Due to hypoxic conditions in the heart which prevents muscle and conductive fibers from maintaining their electrolyte gradients
77
Look at ventricular fibrillation diagram
Look at ventricular fibrillation diagram
78
Look at all EKG pictures
Look at all EKG pictures

Physiology (70 decks)

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