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CV Quiz 2 > Cardiac Arrhythmias > Flashcards

Cardiac Arrhythmias Flashcards

1
Q

Define Bradycardia.

A

Slow heart rate <60/min potentially leading to a decrease in cardiac output, hypotension, heart failure and sx (dizziness, syncope, palpitations)

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2
Q

Define tachycardia.

A

Rapid heart rate >100/min potentially leading to:
• Palpitations
• Impairment of cardiac output, hypotension, heart failure, ischemia and sx

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3
Q

What are palpitations?

A

subjective sense of heart beating abnormally

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4
Q

What is the physiological term for normal heart rate?

A

Normal Sinus Rhythm

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5
Q

Define normal sinus rhythm.

A

Conventionally defined as 60-100/min, but people can be slightly below and slightly above

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6
Q

Define arrhythmia.

A

Literally “No Rhythm” but used to refer to any “Abnormal Rhythm.”

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7
Q

What is bradyarrhythmia?

A
  • Abnormal Bradycardic Rhythm <60/min

* Excludes “normal bradycardia” such as physiologic sinus bradycardia at rest or during sleep

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8
Q

What is tachyarrhythmia?

A
  • Abnormal Tachycardic Rhythm >100/min

* Excludes “normal tachycardia” such as phsyiologic sinus tachycardia during exercise or under stress.

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9
Q

Define supraventricular tachycardia (SVT).

A

Abnormal tachycardia which requires participation of either Atrial or AV Nodal Tissue

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10
Q

When supraventricular tachycardia (SVT) is chaotic what do you call it?

A

Atrial Fibrillation (AF)

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11
Q

Define ventricular tachycardia (VT).

A
  • Abnormal tachycardia originating in the Ventricle or His-Purkinje System (= His Bundle + Bundle Branches + Purkinje Network)
  • By definition, VT does not require involvement of either the Atrium or the AV Node.
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12
Q

When ventricular tachycardia (VT) is chaotic what do you call it?

A

Ventricular Fibrillation (VF)

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13
Q

All disorders of heart rhythm arise as a consequence of either _______ or _______.

A

•Alterations in Impulse Formation or Impulse Conduction (=Propagation)

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14
Q

Normal impulse formation comes from pacemaker cells which are what?

A

Specialized Cardiac Cells with intrinsic automaticity

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15
Q

Failure of faster structures may allows what?

A

subsidiary automatic tissue to exhibit automaticity at slower rates (Called “Escape” Rhythms or Pacemakers)

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16
Q

What provide redundancy in the conduction system and help protect from catastrophic bradycardia?

A

Subsidiary escape pacemakers

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17
Q

Which cells in the heart maintain a very

negative and static resting membrane potential (around -90 mV) and lack intrinsic automaticity?

A

most myocardial cells (working cells)

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18
Q

Sinus Node and AV Node have a higher diastolic membrane postentia, around what?

A

about -60 mV

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19
Q

What is so special about nodal cells?

A

exhibit spontaneous gradual diastolic depolarization

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20
Q

Spontaneous gradual diastolic depolarization is due to what channels?

A

(If): A Slow Inward Sodium Current

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21
Q

Relatively high resting membrane potential of SN and AVN cells keeps most Fast Na channels in the _________ State.

A

Inactivated

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22
Q

If fast Na channels are in an inactivated state, what channels do nodal cells depend on for depolarization?

A

dependence on the slower Ca++ Current

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23
Q

What is overdrive suppression?

A

Faster automatic sites normally preempt subsidiary slower potential pacemaker sites and transiently suppress the rate of subsidiary pacemakers

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24
Q

In spontaneously active pacemaker cells,

hyperpolarizing current of the electrogenic NaK-ATPase is offset by what?

A

the pacemaker current If

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25
Q

in passively activated subsidiary slower pacemaker cells, If is much smaller which leads to what?

A

hyperpolarization

26
Q

So what regulates the sinus node?

A

regulated by autonomic tone to match cardiac output to metabolic demand

27
Q

What 3 factors interplay to create normal automaticity in the node?

A
  • Rate of Diastolic Depolarization (mostly If): Faster depolarization -> faster rate
  • Maximum negative diastolic potential: More negative -> slower rate
  • The Threshold Potential: More negative -> Faster rate & Less negtaive -> Slower rate
28
Q

Near syncope preceded by nausea and cause by increased PNS tone is never lethal because?

A

PNS tone never stays high enough long enough the CNS usually fixes it

29
Q

Two main effects of SNS on automaticity?

A

Increases rate of diastolic depolarization and makes the Threshold Potential More Negative both of which are excitatory

30
Q

Main effects of the PNS on automaticity?

A

Decreases the “Open Probability” of the Pacemaker Current channel (If) and makes Threshold Potential Less Negative

31
Q

during diastole, if adjacent cells have differing diastolic potentials what can happen because they are connected by gap junctions?

A

current may bleed

from one cell to the other following the potential gradient

32
Q

Automaticity will be _______ in Pacemaker
cells tightly coupled to adjacent working
myocardium due to current bleed

A

decreased

33
Q

in the setting of pathologic fibrosis leading to cell decoupling, automaticity may be ________ in pacemaker cells normally inhibited by adjacent working myocardium

A

enhanced

34
Q

A failure of sinus node automaticity is often moderated by emergence of normally suppressed secondary pacemakers in the AV node or, if this has failed too, what takes over?

A

infranodal conduction system

35
Q

An escape rhythm arising in the ______ (termed a Junctional Escape)
will have a narrow QRS without a preceding P-wave and typically a rate
of 50-60/min

A

AV node

36
Q

An escape rhythm arising in the ________ (Ventricular Escape) will have a Wide QRS.

A

Infranodal tissue

37
Q

Increase in rate of tissue normally capable of pacemaker activity is what type of tachycardia mechanism?

A

Enhanced Automaticity

38
Q

Abnormal impulse formation or automaticity in tissue not normally capable of pacemaker activity is what type of tachycardia mechanism?

A

Abnormal Automaticity

39
Q

Abnormal Automaticity is normally caused by what?

A

Often a consequence of cellular injury. May be seen in setting of coronary ischemia, electrolyte disturbances, myocardial disease

40
Q

What is the triggered activity mechanism of tachycardia?

A

Single or repetitive cellular activity following a prior action potential. Due to oscillations in membrane potential

41
Q

There are two types of triggered activity, what are they?

A

Early Afterdepolarizations (EAD’s) and Delayed Afterdepolarizations (DAD’s)

42
Q

What are EAD’s?

A

Membrane Oscillations which occur within the action potential, either in the Plateau (Phase 2) or During Repolarization (Phase 3) related to Inward Ca++ Current (in Phase 2) or reactivation of Fast Na Current (in Phase 3)

43
Q

What are DAD’s?

A

Membrane Oscillations occurring after completion of Full Repolarization (Phase 4) promoted by conditions which lead to high intracellular calcium

44
Q

What do you treat DAD’s with?

A

inhibited by Ca++ channel blockers

45
Q

What is a conduction block?

A

Occurs when a propagating wavefront encounters tissue which is unexcitable

46
Q

What are the three types of conduction block?

A

permanent or fixed
intermittent
functional

47
Q

What does permanent or fixed block mean for conduction?

A

All impulses fail to propagate

48
Q

What does intermittent block mean for conduction?

A

Ability to conduct is variable and changes over time

49
Q

What does functional block mean for conduction?

A

Block may be present only at critical rates which are faster than tissue refractory period will accommodat

50
Q

Block in the _____ or _____ can result in interruption of atrioventricular conduction

A

AV Node or His Bundle

51
Q

What are the classifications of the 3 degrees of AV block?

A

 1st Degree: Delay without failure of conduction
 2nd Degree: Some but not all beats fail to conduct
 3rd Degree: No propagation from Atrium to Ventricle (Also called Complete Heart Block)

52
Q

What does block in the right or left bundle branches do?

A

does not interrupt AV conduction but results in abnormal sequence of ventricular activation reflected in “Bundle Branch Block” patterns on ECG

53
Q

What is electrical reentry?

A

represents abnormal endless loop myocardial propagation and is the the primary mechanism of many important pathologic tachycardias

54
Q

What kind of tissue does reentry occur in?

A

myocardial tissue composed of many myocytes working in sequence

55
Q

What prevents the wavefront from looping back on itself?

A

refractory tissue

56
Q

What are the requirements for reentry to occur?

A

Two Distinct Paths for Propagation, Slowed Conduction in at Least One Path or Unidirectional Block: Tissue capable of conduction in one but not the opposite direction

57
Q

All arrhythmias arise as a consequence of altered impulse what?

A

formation or conduction

58
Q

The normal heart rhythm is initiated by the fastest normal pacemaker tissue in the heart because of what?

A

“Gradient of Automaticity”

59
Q

Abnormal slowing of the sinus node may allow secondary pacemakers to emerge where?

A

AV Node or Infranodal His-Purkinje System

60
Q

Working myocytes are not capable of automaticity but may exhibit _______ or _______ under pathologic conditions which results in ectopic (abnormally located) beats and tachycardia.

A

Abnormal Automaticity or Triggered Activity

61
Q

Failure of conduction may lead to bradycardia by causing _______ or
tachycardia by the mechanism of ________

A

heart block

unidirectional block and Reentry

62
Q

The requirements for reentry are what?

A
  • Two distinct pathways for conduction
  • An area of slowed conduction
  • Functional or Permanent Unidirectional Block

CV Quiz 2 (16 decks)

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