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Pharm 2024 > PPT 14: Cardiac Arrhythmias > Flashcards

PPT 14: Cardiac Arrhythmias Flashcards

Exam 2

1
Q

How prevalent are cardiac arrhythmias in anesthetized patients?

A

50%

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2
Q

What are the types of cardiac arrhythmias?

A
  1. Bradycardia - Slowing (<60 bpm)
  2. Block
  3. Tachycardia
    - Supraventricular (SVT, atrial)
    - Sinus (regular)
    - Ventricular Tachycardia (Vtach)
  4. Fibrillation (Atrial or Ventricular)
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3
Q

What are the components of the intrinsic conduction system of the heart?

A

Sinoatrial node/pacemaker
Atrioventricular node
Atrioventricular bundle/bundle of His
Purkinje fibers

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4
Q

Which part of the intrinsic conduction system is the pacemaker of the heart? What is the contraction rate?

A

SA node - 75 beats/min

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5
Q

The _______ is the crescent shaped node in right atrium of the intrinsic conduction system

A

Sinoatrial node/pacemaker

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6
Q

The _______ is the junction of atria and ventricles of the intrinsic conduction system

A

Atrioventricular node

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7
Q

How fast does the AV node contract?

A

40-50 beats/min - slow

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8
Q

The _______ is in the interventricular septum of the intrinsic conduction system

A

Atrioventricular bundle/bundle of His

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9
Q

The _______ is spread within the muscle of the ventricle walls of the intrinsic conduction system

A

Purkinje fibers

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10
Q

Discuss the changes of the electrocardiogram throughout the intrinsic conduction system

A
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11
Q

Impulses that deviate from the normal electrical pathway are _______

A

Arrhythmias

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12
Q

What are the different types of abnormalities of arrhythmias?

A
  • Site of origin
  • Rate
  • Regularity
  • Conduction
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13
Q

What are the 3 main ions that determine cardiac action potential?

A
  • Sodium
  • Potassium
  • Calcium
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14
Q

Discuss the phases of ion channel currents in cardiac action potential

A
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15
Q

Discuss the three states of sodium channels

A
  1. Resting
    - slowly approaching threshold
    - m gates closed
  2. Activated
    - threshold reached; m gates open
    - massive sodium influx
  3. Inactivated - h gates close
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16
Q

The ________ is the time between the inactivation and resting states of sodium channels

A

Refractory period

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17
Q

K+ channels are open at rest are called ______

A

Inward rectifier channels - Very little flow (electrical gradient)

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18
Q

______ establish the membrane potential of resting cardiac cell

A

K+ current

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19
Q

Ca++ channels open _____ and at more ______ potentials

A

slowly and positive

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20
Q

What are the 2 main classes of arrhythmias?

A
  1. Disturbances in Impulse Formation
  2. Disturbances in Impulse Conduction
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21
Q

What are the types of disturbances in impulse formation that result in arrhythmias?

A
  • Early or late afterdepolarizations
  • SA/AV nodal abnormalities
  • Ion changes
  • SNS stimulation
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22
Q

What are the types of disturbances in impulse conduction that result in arrhythmias?

A
  • Block
  • Reentry
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23
Q

Abnormal depolarizations that occur during phase 2, 3, or 4

A

Afterdepolarizations (AD)

24
Q

Differentiate between Early (EAD) and Delayed Afterdepolarizations (DAD)

A

Early Afterdepolarizations (EAD)
- Phase 2 or 3
- Sodium or calcium channels

Delayed Afterpolarizations (DAD)
- Occur before a normal action potential
- Elevated intercellular calcium

25
Q

Severe depression of conduction may result in ______

A

block

26
Q

Discuss the ECG changes of the various degrees of heart block

A
27
Q

________ inhibits conduction of depolarization

A

Heart block

28
Q

What is considered “blocked” in heart block?

A
  • AV nodal block
  • Bundle branch block
  • Block – allows one-way conduction
29
Q

Describe the reentry block and “circus movement”

A

One impulse “circles around” and re-excites areas more than once

30
Q

What must happen in order for reentry to occur?

A
  • There must be an obstacle (scar tissue)
  • Block must be unidirectional
  • Conduction time must be long enough to reenter same areas after refractory period
31
Q

How is heart block treated?

A
  • Type II/III: Transcutaneous pacing, pacemaker
  • Pharmacology (reentry):
    a. Slow down circular current – sync with next action potential
    - Drugs – block sodium or calcium current
    b. Lengthen or shorten refractory period
32
Q

What are the 4 classes of antiarrhythmic agents?

A

Vaughan-Williams classification:
- Class I – sodium channel blockade
- Class II – sympatholytic (beta blockers)
- Class III – prolong action potential duration (other mechanisms besides sodium channels – K+)
- Class IV – block cardiac calcium channel currents

33
Q

What are the 3 subclasses of Class I antiarrhythmic agents?

A

IA, IB, IC

34
Q

What meds are included in Class IA antiarrhythmic agents? What are the effects on APD and ERP? What are the cardiac effects?

A

Quinidine (Procainimide, Disopyramide)
- Prolong the action potential duration (APD)
- ↑ Effective Refractory Period (ERP)
- Cardiac effects: Depresses pacemaker rate, Lengthens QT interval, Depresses conduction and excitability

35
Q

What meds are included in Class IB antiarrhythmic agents? What are the effects on APD and ERP?

A

Lidocaine
- Shorten the APD
- ↓ ERP

36
Q

What meds are included in Class IC antiarrhythmic agents? What are the effects on APD and ERP?

A

Flecainide
- Minimal effects on APD
- Slow dissociation
- No effect on ERP (But Na+ channels are still blocked)

37
Q

What meds are included in Class II antiarrhythmic agents? How do these agents work as antiarrhythmics?

A

Beta blockers - propanolol and esmolol (short acting)
- Antiarrhythmic properties associated with direct membrane effects - Exact antiarrhythmic action unknown
- Suppress ventricular ectopic depolarization
- Prevent infarction and sudden death in patients recovering from acute MI

38
Q

What meds are included in Class III antiarrhythmic agents? How do these agents work as antiarrhythmics?

A

Amiodarone (VT) and dronedarone (A-fib)
Prolong AP usually by:
- Blocking cardiac K+ channels
- Enhancing inward current (Na+ or Ca2+ channels)

39
Q

What meds are included in Class IV antiarrhythmic agents? How do these agents work as antiarrhythmics?

A

Calcium channel blockers - verapamil
- Prolongs AV node conduction
- Slows SA node
- Hypotensive action
- Useful for supraventricular arrhythmias
- Can reduce ventricular rate in atrial fibrillation and flutter

40
Q

What are the antiarrhythmic agents that do not fit into the conventional classes?

A
  • Digoxin
  • Adenosine - SVT, Enhanced K+ conductance, Inhibition of cAMP induced calcium influx
  • Magnesium - digitalis induced arrhythmias
  • Potassium - normalizing levels
41
Q

What are the non-pharmacologic interventions used to treat arrhythmias?

A
  • Vagal maneuvers
  • Pacemakers
  • Cardioversion
  • Catheter ablation
  • Surgery
42
Q

What is the treatment for symptomatic bradycardia?

A

1st - atropine
2nd - epi, dopamine

43
Q

What is the treatment for chronic bradycardia?

A

pacemaker

44
Q

What is the treatment for symptomatic heart block?

A

atropine and transcutaneous pacing

45
Q

What is the treatment for chronic heart block?

A

pacemaker

46
Q

What is the treatment for symptomatic SVT?

A

adenosine

47
Q

What is the treatment for chronic SVT?

A

CCBs, beta blockers

48
Q

What is the treatment for symptomatic sinus tachycardia?

A

Adenosine, CCBs, cardioversion

49
Q

What is the treatment for chronic sinus tachycardia?

A

catheter ablation

50
Q

What is the treatment for symptomatic Vtach?

A

amiodarone

51
Q

What is the treatment for chronic Vtach?

A

amiodarone, satolol

52
Q

What is the treatment for symptomatic Afib?

A

diltiazem, verapamil

53
Q

What is the treatment for chronic Afib?

A

beta-blockers, amiodarone

54
Q

What is the treatment for symptomatic Vfib?

A

CPR, defirillation

55
Q

What is the treatment for chronic Vfib?

A

amiodarone, lidocaine

Pharm 2024 (28 decks)

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