Cardiac arrhythmas Flashcards Preview

A. White- Human Physiology > Cardiac arrhythmas > Flashcards

Flashcards in Cardiac arrhythmas Deck (44):
1

Define Tachyardia

Fast heart rate (>100 beats/min)

2

What are some causes of Tachycardia?

  1. increased body temperature
  2. stimulation of the heart by the sympathetic nerves
  3. toxic conditions of the heart

3

Define Bradycardia

Slow heart rate (<60 beats/min)

4

What are some causes of bradycardia?

  • athletic heart
  • vagal stimulation (parasympathetic stimulation)
  • extremely sensitive carotid baroreceptors in carotid sinus syndrome

5

What arrhythmia is present?

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Atrial fibrillation

6

What arrhythmia is present?

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Atrial paroxysmal tachycardia

7

What arrhythmia is present?

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Atrial premature beat

8

What arrhythmia is present?

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A-V nodal premature contraction

9

What arrhythmia is present?

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Complete A-V block

10

What arrhythmia is present?

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Partial intraventricular block

11

What arrhythmia is present?

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First degree A-V heart block

12

What arrhythmia is present?

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Second degree A-V block

13

What arrhythmia is present?

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Sinoatrial nodal block

14

What arrhythmia is present?

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Sinus bradycardia

15

What arrhythmia is present?

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Tachycardia

16

What arrhythmia is present?

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Ventricular fibrillation

17

What arrhythmia is present?

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ventricular paroxysmal tachycardia

18

What are some physiological results of endogenously mediated tachycardia?

  • heart rate increases
  • cardiac output increase
  • filling time is reduced but stroke volume does not fall

19

What are som physiological results of pathologically mediated tachycardia?

  • heart rate increases
  • cardiac output decreases

20

What are spillover signals?

Signals sent from the medullary respiratory center into the vasomotor center during inspiratory and expiratory respiratory signals

- These signals alternately increase and decrease the number of impulses transmitted through sympathetic and vagus nerves through the heart

21

What are the characteristics of a sinoatrial block?

  • sudden cessation of P waves
  • resultant standstill of atria
  • ventricles pick up a new rhythm, usually in the AV node
  • rate of QRS is slowed but not otherwise altered

22

What would be some conditions that would cause an atrioventricular block?

  1. ischemia of AV node od Av bundle fibers through coronary insufficieny
  2. compression of AV bundle by scar tissue or calcified portions of the heart
  3. inflammation of the AV node or bundle
  4. extreme stimulation of the heart by the vagus nerves

23

What are the two types of incomplete atrioventricular block?

  1. First-degree
  2. second-degree

24

What characterizes a first-degree A-V block?

When P-R interval increases to greater than 0.20 sec. (normal is 0.16)

25

What is the normal P-R time interval?

0.16 sec

26

What characterizes a second-degre A-V block?

  • P-R interval increases to 0.25 to 0.45 sec
  • Atrial P wave is present but QRS-T wave may be missing, resulting in dropped beats of the ventricle
  • 2:1 rhythm or other variations may develop

27

Periodic fainting spells due to a complete A-V block is referred to as what?

Stokes-Adam syndrome

28

Patients will often faint due to a lack of blood to the brain until the ventricles escape because of what type of block?

A complete A-V block

29

A partial intraventricular block is can be also referred to as what?

Electrical alternans

30

What term refers to an alteration in the amplitude of P waves, QRS complexes, or T waves?

Electrical alternans

31

Most premature contractions result from what?

Ectopic foci in the heart

32

Name 2 of the 3 possible causes of ectopic foci.

  1. local areas of ischemia
  2. calcified plaques
  3. toxic irritation of the conduction system or nodes

33

What does the term paroxysmal mean?

It means that the heart rate becomes rapid in paroxysms

34

What are some characteristics of paroxysmal tachycardia?

  • paroxysms beigin suddenly and can last for seconds, minutes, hours, or longe
  • paroxysms end suddenly
  • pacemaker of the heart instantly shifts back to the sinus node

 

35

What is the physiological basis behind fibrillation?

The normal ventricular depolarization waves die out because the heart muscle that has already contracted is in the refractory period and cannot respond to being stimulated by the existing depolarization waves

36

What is fibrillation?

The twitching (usually slow) of individual muscle fibers in the atria or ventricles and also recently denervated skeletal muscle fibers.

37

Fibrillation occurs as a reult of these?

Circus movements

38

List 2 of the 3 conditions that cause the impulse to travel in around the circle (circus movements)?

  1. the pathway around the circle is too long
  2. the length of the pathway remains constant but the velocity of the conduction slows down
  3. the refractory period of the muscle might become greatly shortened

39

What do circus movements occur if the pathway around the cirle is too long?

By the time to impulse returns to its starting point the originally stimulated muscle will no longer be in the refractory period and the impulse will continue around the circle again and again.

-Chareacteristic of dilated hearts

40

Whay do circus movements occur when the length of the pathway remains constant but the velocity of the conduction slows down?

An increased amount of time will elaspe before the impulse returns to its original position. By this time, the originally stimulated muscle might be out of the refractory period, and the impulse can continue around the circle again and again.

-Characteristic of blockage of the Purkinje system, ischemia, or high potassium levels.

41

Why do circus movements occur when the refractory period of the muscle is shortened?

With a shorter refrractory period the impulse could continue around the circle again and again.

- May occur in reponse to drugs such as epinephrine or after repetitive electrical stimulation

42

The atrial muscle fibers are seperated from the ventriculoar muscle fibers by the _______ _______ _______?

Cardiac fibrous skeleton

43

True or False: ventricular and atrial fibrillation may occur seperate from one another?

True

44

What are some causes for atrial fibrillation?

- Enlargement of the atria (due to valve lesions)

- Inadequate emptying of the ventricles causing blood to back up into the atria