Exam 3: Anti-Arrhythmic Agents Flashcards Preview

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Flashcards in Exam 3: Anti-Arrhythmic Agents Deck (119):
1

Phase 0:

Rapid depolarization; fast inward Na+ flow; upstroke of action potential graph

2

Phase 1:

Partial repolarization; Na+ channels close; 'peak' of AP graph

3

Phase 2:

Plateau; slow Ca2+ channels open; flat 'pause' on AP graph

4

Phase 3:

Repolarization; Ca2+ channels close; K+ channels open; downstroke on AP graph

5

Phase 4:

Pacemaker potential; slow upward stroke between APs

6

Which phases are refractory?

1-3

7

Normal SA rate:

60-100

8

Normal AV rate:

40-60

9

SA node resting potential:

-55 mV

10

Purkinje fiber firing rate:

15-30

11

Receptors in the atria that affect the SA node:

β1 and M2

12

Two types of defects in electrical activity:

Defect in formation of impulse
Defect in conduction of impulse

13

Define altered automaticity:

Latent pacemaker cells take over the SA node's role; escape beats

14

Define delayed after-depolarization:

Normal AP of cardiac cell triggers train of abnormal depolarizations

15

Define re-entry:

Refractory tissue reactivates repeatedly/rapidly due to unidirectional block, which causes a circuit effect

16

Define conduction block:

Impulses that fail to propagate in non-conducting tissue (like MI-injured heart)

17

Causes of delayed after-depolarization:

Electrolyte abnormalities
Drug toxicities

18

Most common way arrhythmias are formed:

Re-entry

19

Arrythmias require tx when:

Cause cannot be corrected
Hemodynamic function compromised
Arrhythmia can cause more serious arrhythmias or comorbidities

20

Acute non-pharmacological tx of arrhythmias:

Vagal maneuvers
Cardioversion

21

Prophylactic non-pharmacological tx of arrhythmias:

Radiofrequency catheter ablation
Implantable defibrillator

22

Class I antiarrhythmic drugs:

Na+ channel blockers

23

Class II antiarrhythmic drugs:

β-blockers

24

Class III antiarrhythmic drugs:

K+ channel blockers

25

Class IV antiarrhythmic drugs:

Ca+ channel blockers

26

Class V antiarrhythmic drugs:

Unclassified

27

Class Ia agents are:

Intermediate Na+ channel blockers

28

Effects of class Ia agents:

↓ depolarization rate
↓ conduction velocity
Prolonged repolarization
↑ AP duration

29

Class Ia prototype and examples:

Quinidine*
Procainamide
Disopyramide
Moricizine

30

Indications for disopyramide:

Suppress atrial/ventricular tachyarrhythmia

31

S/E of disopyramide:

Myocardial depression
Can precipitate CHF/HoTN

32

Class Ib agents are:

Fast Na+ channel blocker

33

MoA of class Ib agents:

Blocks Na+ channels; doesn't affect the rate of depolarization, but shortens AP duration and refractory

34

Prototype and examples of class Ib agents:

Lidocaine*
Mexiletine
Tocainide
Phenytoin

35

Indications for lidocaine:

Acute tx/prevention of ventricular dysrhythmias esp. immediately after MI

36

Lidocaine used after MI because:

Raises the vfib threshold

37

Dosing for lidocaine:

1 - 1.5 mg/kg IV
Infusion: 1-4 mg/min
Max dose: 3 mg/kg

38

PK of lidocaine:

50% protein bound
Hepatic metabolism with an active metabolite
10% renal elimination

39

Drugs/conditions that impair metabolism of lidocaine:

Cimetidine
Propranolol

CHF, MI, liver dysfunction, GA

40

Drugs that induce metabolism of lidocaine:

Barbiturates
Phenytoin
Rifampin

41

Half-time of lidocaine:

1.4 - 8 hrs

42

Therapeutic concentration of lidocaine:

1-5 mcg/ml

43

Indication for mexiletine:

Oral/chronic suppression of ventricular tachyarrhythmias

44

Class Ic agents are:

Slow Na+ channel blockers

45

MoA of class Ic agents:

Potent decrease of depolarization rate, decrease of conduction rate, increased AP

46

Prototype and examples of class Ic agents:

Flecainide*
Propafenone

47

Indications for flecainide or propafenone:

Ventricular PVCs, v-tach
Atrial tachyarrhythmias
WPW (flecainide)

48

S/E of flecainide:

Proarrhythmic

49

MoA of class II agents:

Depress spontaneous phase 4 depolarization, decreasing SA node discharge

↓ conduction through AV node
↓ contractility

50

Indications for class II agents:

SVT, atrial and ventricular arrhythmias

Ventricular dysrhythmias during MI/reperfusion

Tachyarrhythmias 2/2 digoxin toxicity

51

Prototype and examples of class II agents:

Propranolol*
Metoprolol
Esmolol
Labetalol

52

Indications for propranolol:

Prevent recurrence of tachyarrhythmias (both SVT and VT) from SNS stimulation

53

Dosing of propranolol:

1 mg/min (total 3-6 mg) IV
10-80 mg PO

54

Onset, peak, duration, half-time of propranolol:

Onset: 2-5 min
Peak: 10-15 min
Duration: 3-4 hrs
E1/2t: 2-4 hrs

55

Cardiac effects of propranolol:

↓ HR, contractility, CO
↑ PVR, coronary VR

56

PK of propranolol:

Highly protein-bound
Hepatic metabolism (weak metabolite)

57

Therapeutic plasma level of propranolol:

10-30 ng/ml

58

S/E of propranolol:

Bradycardia
Hypotension
Myocardial depression
Fatigue
Bronchospasm
Drug fever
Rash
Nausea
Raynaud's
Glucose interference

59

Precautions for propranolol:

Reactive airway disease
Hypovolemia
CHF
AV block

60

Dosing for metoprolol:

5mg IV over 5 min
Max dose 15 mg over 20 min

61

Onset, duration, half-life of metoprolol:

Onset: 2.5 min
E1/2t: 3-4 hrs

62

Metabolism of metoprolol:

Metabolized by liver

63

Dosing of esmolol:

0.5 mg/kg IV bolus
Infusion: 50-300 mcg/kg/min

64

Duration of esmolol:

< 15 min

65

Clinical effect of esmolol:

↓ HR without significantly ↓ BP at small doses

66

Metabolism of esmolol:

Plasma esterases (not the same as sux ones)

67

MoA of class III agents:

↓ conduction velocity and prolong refractory period/action potential

68

Indications for class III agents:

SV/V arrhythmias
Prophylaxis during cardiac surgery r/t a-fib
Preventative tx for patients w/ past cardiac death who cannot have AICD

69

Prototype and examples of class III agents:

Amiodarone*
Dronedarone
Sotalol

70

Amiodarine has properties of these classes:

III primarily
Also I, II, IV

71

MoA of amiodarone:

K+/Na+/Ca+ channel blocker
ɑ- and β-blocker

72

Indications for amiodarone:

Prophylaxis or acute tx of atrial and ventricular arrhythmias

73

Amiodarone is 1st line drug when:

Heart is resistant to electrical defibrillation

74

Dosing of amiodarone:

Bolus 150-300mg over 2-5 min (up to 5 mg/kg)
Infusion: 1mg/hr x 6hr, 0.5 mg/hr x 18hr

75

Half-time of amiodarone:

29 days!!

76

Metabolism of amiodarone:

Hepatic metabolism
Biliary/intestinal excretion

77

Therapeutic level of amiodarone:

1.0 - 3.5 mcg/ml

78

Protein binding/Vd of amiodarone:

96% protein bound
Huge Vd (extensively taken into tissues)

79

Administration consideration with amiodarone:

Can cause phlebitis - give in a large vein

80

Pulmonary S/E and considerations of amiodarine:

Pneumonitis, fibrosis, edema, ARDS (all related to ROS) - high FiO2 can exacerbate so keep it low

81

MoA of class IV agents:

Block slow calcium channels, primarily in the AV node

Shortens phase 2 in myocytes to ↓ contractility

82

Indications for class IV agents:

SVT and rate control in afib/aflutter
NOT used for vent arrhythmias

83

Prototype and examples of class IV agents:

Verapamil*
Diltiazem

84

Dosing for verapamil:

2.5 - 10mg IV over 1-3 mins (max 20mg)
Infusion: 5 mcg/kg/min

85

Contraindicated drug with verapamil:

β-blockers

86

PK of verapamil:

Highly protein bound
Hepatic metabolism - active metabolite
Excreted in urine/bile

87

Half-time of verapamil:

6-8 hrs

88

S/E of verapamil:

Myocardial depression
Hypotension
Bradycardia
Nausea
Prolongation of NMBs

89

Dosing of diltiazem:

5-20 mg IV over 2 min
Infusion: 10 mg/hr

90

Diltiazem vs. verapamil:

Diltiazem has less myocardial depression and less interaction with β blockers

91

PK of diltiazem:

E1/2t: 4-6 hrs
Highly protein bound
Hepatic metabolism
Excreted in urine

92

S/E of diltiazem:

Myocardial depression
Hypotension
Constipation
Bradycardia
Nausea
Prolongation of NMBs

93

Examples of class V agents:

Adenosine
Digoxin
Phenytoin
Atropine

94

MoA of adenosine:

Binds to A1 purine nucleotide receptors; activates adenosine receptors to open K+ channels/increase K+ current)

End result: slows SA and AV node conduction

95

Indications for adenosine:

Termination of SVT or diagnose VT

96

Dosing for adenosine:

6mg IV, rapid bolus followed by flush
Repeat if needed at 3 minutes, another 6-12mg IV

97

Half-time of adenosine:

< 10 seconds

98

Metabolism of adenosine:

Plasma/vascular endothelial cell enzymes

99

S/E of adenosine:

Excessive SA/AV node inhibition
Flushing
Headache
Dyspnea
Chest discomfort
Nausea
Bronchospasm

100

Contraindications for adenosine:

Asthma
Heart block

101

MoA of digoxin:

Increases vagal activity, thus ↓ activity of SA node/prolongs AV conduction

↓ HR, preload, afterload

Also positive inotrope

102

Dosing of digoxin:

0.5 - 1mg, divided doses over 12-24 hrs

103

Onset, half-time of digoxin:

Onset: 30-60 min
E1/2t: 36 hrs

104

Therapeutic level of digoxin:

0.5 - 1.2 ng/dl

105

PK of digoxin:

Weak protein binding
90% excreted by kidneys

106

S/E of digoxin:

Arrythymias, heart block, anorexia, nausea, diarrhea, confusion, agitation

107

Digoxin S/E potentiated by:

Hypokalemia, hypomagnesemia

108

Tx for digoxin toxicity:

Vent. arrhythmias: phenytoin
Pacing
Atropine
Antidote: digoxin immune Fab

109

Indications for phenytoin:

Suppression of vent. arrhythmias from digoxin toxicity

Refractory torsades de pointes

110

Dosage of phenytoin:

1.5 mg/kg IV every 5 min, up to 10-15 mg/kg
Can be painful IV!

111

Therapeutic levels of phenytoin:

10-18 mcg/ml

112

Indications for atropine:

Unstable bradyarrhythmias

Option for asystolic/PEA

113

Dosage for atropine:

0.4 to 1.0 mg IV, repeat as necessary

114

Onset/duration for atropine:

Onset: 1 min
Duration: 30-60 min

115

Metabolism of atropine:

Hepatic

116

Precaution with atropine dosing:

Less than 0.4mg can have paradoxical response
Penetrates BBB; has CNS effects

117

Drugs for afib during arthoscopy:

Good heart function: amiodarone
Poor heart function: digoxin

118

Drugs for SVT during a laparoscopy:

Normal heart function: CCB (diltiazem), β-blocker
Impaired heart function: no cardioversion; digoxin or amiodarone

119

Drugs for V-tach during AAA:

Defib first if unstable!
Amiodarone, lidocaine, procainamide