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TERM 3 BIOL2292 PATHO 2 > CARDIAC LECTURE 4: DYSRHYTHMIAS > Flashcards

CARDIAC LECTURE 4: DYSRHYTHMIAS Flashcards

1
Q

What are the 2 functions of the autorhythmic fibers of the heart?

A
  1. Spontaneously depolarize to create action potentials
  2. Propagate/conduct action potentials through the heart
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2
Q

What is the name of the pacemaker of the heart, and where is it located?

A

Sinuatrial node, located in the right atrium superiorly

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3
Q

What is the function of the AV node?

A

Delays signals before transmission to AV bundle

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4
Q

After transmission to the AV bundle, where do electrical signals travel?

A

Right and left bundle branches

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5
Q

After transmission to bundle branches, where do electrical signals travel?

A

Subendocardial conducting network (Purkinje fibers)

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6
Q

After spontaneous depolarization, what causes rapid depolarization in the SA node?

A

Sodium influx through voltage gated fast channels

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7
Q

What causes the plateau/maintained depolarization in the sinoatrial node?

A
  1. Calcium influx through voltage gated slow channels
  2. Potassium outflow through some channels
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8
Q

What causes repolarization of the sinoatrial node?

A
  1. Calcium channels close
  2. Potassium outflow when more channels open
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9
Q

What prevents the membrane from depolarizing too soon after the previous action potential?

A

Refractory period

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10
Q

What are 3 possible mechanisms that cause dysrhythmias, and which is most common?

A
  1. Abnormal automaticity
  2. Triggered activity from depolarization
  3. Reentrant circuits (most common)
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11
Q

What is the meant by abnormal automaticity?

A
  1. Too fast/slow rate of depolarization generation
  2. Ectopic impulse generation
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12
Q

What is an example of a cause for abnormal automaticity?

A

Ischemia causes ATP depletion, which disrupts ion gradients

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13
Q

What is meant by triggered activity from depolarization?

A

Impulse generated during or just after repolarization

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14
Q

What is an example of a cause for triggered activity?

A

Genetic abnormalities/drugs alter calcium homeostasis

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15
Q

What is meant by reentrant circuits?

A

Cardiac impulse continues depolarizing a part of the heart after repolarization

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16
Q

What are 2 examples of causes for reentry?

A
  1. Cardiac scarring
  2. Mutations of genes that code for gap junction proteins
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17
Q

What is the purpose of a 12-lead ecg?

A

Measure the electrical activity of the heart from all angles

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18
Q

What does the P wave indicate?

A

SA node and atrial depolarization

19
Q

What does the QRS complex indicate?

A

Ventricular depolarization

20
Q

What does the T wave indicate?

A

Ventricular repolarization

21
Q

What unit of time does one large box indicate on the ECG strip?

A

0.2 seconds

22
Q

What are the 3 major types of cardiac dysrhythmias?

A
  1. Abnormal rates of sinus rhythm
  2. Ectopic sites of impulse initiation
  3. Disturbances in conduction pathways
23
Q

What are treatments for sinus bradycardia?

A
  1. Drugs that activate sympathetic nervous system
  2. Drugs that block parasympathetic nervous system
24
Q

What are 2 causes for ectopic sites of initiation?

A
  1. If the SA node fails then a slower pacemaker will take over
  2. Any premature depolarization that overrides the SA node
25
Q

What does an atrial flutter look like on the ECG?

A

Sawtooth pattern, regular ventricular rate/rhythm

26
Q

What is the most common reason for atrial flutter?

A

Reentrant rhythm in atria (continue depolarizing in atria even after repolarization everywhere else)

27
Q

Why does atrial flutter not cause the ventricles to flutter as well?

A

AV node has a long refractory period so not all atrial depolarizations get through

28
Q

What does atrial fibrillation look like on an ECG?

A

Irregular atrial rhythm (squiggles), irregular ventricular rhythm (not evenly spaced)

29
Q

What is the cause of atrial fibrillation?

A

Rapid depolarizations from numerous ectopic sites

30
Q

Why does atrial fibrillation involve irregular ventricular rhythm?

A

Ventricles only contract during occasional depolarizations near the AV node

31
Q

What does ventricular tachycardia look like on an ECG?

A

“Tombstones” Wide QRS complexes at >100bpm

32
Q

What is the mechanism that causes v-tach?

A

Ectopic site within ventricle spreads throughout ventricular region

33
Q

What may induce v-tach?

A
  1. Hypoxia
  2. Hypokalemia
  3. HF
  4. Sympathetic stimulation
34
Q

What does ventricular fibrillation look like on an ECG?

A

No discernable waves, just one long squiggle

35
Q

What is the mechanism behind v-fib?

A

Multiple foci fire in a chaotic manner, producing quivering myocardium (no pumping)

36
Q

What is the term for a dysrythmia where there is a problem between sinus impulse and ventricular response, either slowed or completely blocked?

A

Atrioventricular block

37
Q

What type of AV block shows a prolonged PR interval (slowed ventricular contraction) and is usually asymptomatic?

A

1st degree block

38
Q

Which type of AV block involves intermittent atrial conduction to ventricles?

A

2nd degree

39
Q

What are 2 types of 2nd degree AV block?

A
  1. Irregular rate: PR intervals progressively lengthen until one QRS complex is dropped
  2. Regular rate: A few P waves before a QRS complex
40
Q

Which type of AV block involves complete block of atrial conduction to ventricles, where the ventricles are paced by an independent pacemaker site?

A

3rd degree

41
Q

What is the treatment for 3rd degree AV block?

A

Transcutaneous pacing or pacemaker

42
Q

What are 4 methods of treatment for dysrhythmias?

A
  1. Vagal maneuvers (stimulate parasympathetic nervous system)
  2. Ablation (destroy abnormal tissue)
  3. Electrical interventions
  4. Anti-arrhythmic drugs
43
Q

What are 3 electrical interventions for dysrhythmias?

A
  1. Pacemakers
  2. Cardioversion (with pulse)
  3. Defibrillation (without pulse)
44
Q

What are 4 kinds of anti-arrhythmic drugs?

A

Class 1: Sodium channel blockers
Decrease depolarization and atrial contraction

Class 2: Beta blockers
Decrease SNS activity to slow heart rate and decrease contractility

Class 3: Potassium channel blockers, and Class 4: Calcium channel blockers
Prolong AP time and refractory period

TERM 3 BIOL2292 PATHO 2 (19 decks)

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