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Block 3 physiology > Cardiac Conduction Disorders: Rhythm and Rate > Flashcards

Cardiac Conduction Disorders: Rhythm and Rate Flashcards

1
Q

Manifested by multiple P wave shapes and PR intervals

A

wandering pacemaker

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2
Q

Describe SA node beats

A

smooth upright P waves

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3
Q

Describe non-SA node beats

A

flattened, notched, biphasic (S-shaped) or inverted P waves

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4
Q

Wandering pacemaker: ________ contraction is normal, so the QRS complex is ______ width and height

A

Wandering pacemaker: ventricular contraction is normal, so the QRS complex is normal width and height

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5
Q

What may precipitate a wandering pacemaker

A

reduced SA node firing

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6
Q

Most common in very young, very old, athletes, rarely causes symptoms or requires treatment

A

wandering pacemaker

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7
Q

EKG characteristics of wandering pacemaker

A
  • rate <100
  • P wave shape varies
  • Irregular ventricular rhythm
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8
Q

Occurs when tachycardia occurs at the same time as wandering pacemaker

A

multifocal atrial tachycardia

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9
Q

EKG characteristics of multifocal atrial tachycardia

A
  • rate >100
  • P wave shape varies
  • Irregular ventricular rhythm
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10
Q

Caused by very rapidly firing ectopic atrial foci

A

atrial fibrillation

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11
Q

What does very rapidly firing ectopic atrial foci result in?

A

results in uncoordinated, ineffective, irregular atrial contraction

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12
Q

What is the irregular atrial contraction due to?

A

due to occasional impulses resulting in AV node discharge

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13
Q

How long does atrial fibrillation last?

A

may occur suddenly and last for minutes to days OR be permanent

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14
Q

EKG characteristics of atrial fibrillation

A
  • P waves absent
  • usually normal QRS width
  • Irregularly irregular rhythm
  • continuous chaotic atrial spikes
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15
Q

occur after the controlling automaticity focus (usually the SA node) stops pacing (“sinus arrest”)

A

escape rhythms

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16
Q

occurs when a transient pacer escape occurs and resumes after one beat

A

escape beat

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17
Q

occurs when the SA node stops firing

A

sinus arrest

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18
Q

occurs when another atrial pacer takes over the rhythm

A

atrial escape rhythm

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19
Q

EKG change with atrial escape rhythm

A
  • different P wave

- same QRS

20
Q

Occurs when the AV node (or a nearby focus) takes over following sinus arrest

A

junctional escape rhythm

21
Q

EKG change with junctional escape rhythm

A
  • loss of P wave (buried in another wave) OR P wave may occur before or after QRS wave
  • unusual P wave shape
  • QRS complex usually unchanged
22
Q

Occurs when pacing fails to occur from more superior pacers (e.g., SA, AV) and automaticity foci in the ventricles take over

A

ventricular escape rhythm

23
Q

EKG change with ventricular escape rhythm

A
  • loss of P wave or P wave not conducting

- wide QRS complex

24
Q

What do ventricular escape rhythms usually result from?

A

ventricular automaticity focus activation

25
Q

Following sinus ____ (or block) another _____ will take over, resulting in an ______ _____.

A

Following sinus arrest (or block) another pacer will take over, resulting in an escape beat.

26
Q

originate early from an “irritable” automaticity focus

A

premature beats

27
Q

Causes of atrial and junctional focus irritability include:

A
  • Epinephrine
  • Sympathetic stimulation
  • B1 stimulants (caffeine, amphetamines, cocaine)
  • Drugs (excess digitalis, ethanol)
  • Hyperthyroidism
  • Cardiac stretch (heart failure)
  • Low oxygen
28
Q

Which automaticity foci are particularly susceptible to low oxygen tension, hypokalemia, excess stretch, etc?

A

ventricular automaticity foci

29
Q

usually result in a change in rhythm (shortened) followed by a prolonged period after which the SA node resets and takes over

A

premature atrial beats/contraction (PAB, PAC)

30
Q

EKG change with premature atrial beats

A

-different shaped P wave with normal QRS wave

31
Q

arise from an irritable atrial focus, causing premature atrial depolarization

A

premature atrial beats

32
Q

What are some other EKG changes that may result from premature atrial beats?

A
  • May result in aberrant ventricular conduction if one bundle branch has not repolarized fully (wide QRS)
  • If AV node does not conduct the PAB, a QRS complex is absent
33
Q

occurs when each normal beat is followed by an abnormal PAB

A

atrial bigeminy

34
Q

occurs when two normal beats are followed by an abnormal PAB

A

atrial trigeminy

35
Q

Premature beats may originate at an irritable automaticity focus in the AV node (junction), resulting in what?

A

premature junctional beat

36
Q

EKG changes with premature junctional beat

A
  • Occur prematurely – early
  • P waves may be buried in the QRS wave, occur before or after, or not be conducted
  • The QRS complex may be normal, or wider than normal due to incompletely repolarized bundle branches
37
Q

result when an irritable ventricular automaticity focus fires unexpectedly

A

premature ventricular contractions

38
Q

EKG changes with premature ventricular contractions

A
  • Occur prematurely
  • No P wave
  • The impulse is slowly transmitted to the rest of the ventricles through the myocardium, producing a wide QRS wave and bizarre T wave
39
Q

Why does it take a long time for full depolarization to cure with premature ventricular beats?

A

Because the ventricular wall conducts slowly (via cardiomyocyte conduction rather than through the conduction system)

40
Q

What does the shape of the wave depend on for premature ventricular beats?

A

The shape of the wave will depend on where the depolarization begins

41
Q

What generally follows a PVC? Why?

A

there is generally a compensatory pause as the ventricles repolarize

42
Q

Why might there be P waves occurring with PVC?

A

There may be P waves occurring from independent atrial depolarization

43
Q

Why might multiple PVCs may occur?

A

if the ventricular automaticity focus is very irritable (e.g., poor oxygenation, epinephrine, β-agonists)

44
Q

What may multiple PVCs result in?

A
  • ventricular bigeminy
  • ventricular trigeminy
  • ventricular tachycardia
45
Q

If all PVCs originate from the same ____ the QRS waves will have the same _____.

A

If all PVCs originate from the same focus the QRS waves will have the same shape.

46
Q

If the PVCs originate from _____ foci the ____ waves will look different.

A

If the PVCs originate from multiple foci the QRS waves will look different.

Block 3 physiology (6 decks)

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