Dysrhythmia Flashcards
(83 cards)
1
Q
Autorhythmic cells
A
Cardiac cells in the heart that create their own resting membrane potential.
2
Q
Contractile cells
A
Cardiac cells responsible for the heart’s pumping activity.
3
Q
Automaticity
A
Relates to heart’s ability to spontaneously generate an electrical impulse.
4
Q
Depolarization
A
Electrical stimulation or impulse that generates an action potential.
5
Q
Repolarization
A
Movement of membrane potential to initial resting (polarized) state.
6
Q
Conduction velocity
A
Speed in which electrical impulse is transmitted.
7
Q
Refractory period
A
Time-frame after depolarization where cells cannot be excited again.
8
Q
Absolute refractory period
A
In-excitable period regardless of impulse strength
9
Q
Relative refractory period
A
Cell is partially repolarized; Strong stimulus could cause depolarization
10
Q
Vaughan-William Classification
A
- Class I Agents - Sodium channel blockers
- Class II Agents - beta blockers
- Class III Agents - Potassium channel blockers
- Class IV Agents - Non-dihydropyridine calcium channel blockers
11
Q
Which of the Vaughan-William Classifications can cause QT prolongation?
A
- Class IA
- Class III
12
Q
What are the agents in Class I?
A
- IA: Disopyramide, Quinidine, Procainamide
- IB: Lidocaine, Mexiletine, Phenytoin
- IC: Flecainide, Propafenone
13
Q
What are the agents in Class II?
A
beta blockers
14
Q
What are the agents in Class III?
A
- Amiodarone
- Dronedarone
- Sotalol
- Dofetilide
15
Q
What are the agents in Class IV?
A
Non-dihydropyridine calcium channel blockers
16
Q
Class I pharmacotherapy
A
- block Na channels (inhibit phase 0)
- C > A > B
- Delay automaticity
- Slows conduction velocity
- Varying effects on repolarization
17
Q
Class I pearls
A
- use dependence; work better at faster heart rates
- need TDM
- can be pro-dysrhythmic
- avoid in pts with structural heart disease or CAD (linked to higher morbidity and mortality rates)
18
Q
Class IA actions
A
- Moderate inhibition of Phase 0
- Prolongs absolute refractory period
- Prolongs repolarization
19
Q
Procainamide
A
- Class IA
- Ventricular arrhythmias (V. tachycardia, V. fib)
- NAPA metabolite (acts like a Class III) which will cause more QT prolongation effects
- 2D6 substrate
- acute ethanol reduces serum concentraiton
- dose adjust in renal impairment (CrCl < 50 mL/min) and hepatic impairment
- TDM
20
Q
Disopyramide
A
- Norpace®
- Class IA
- Ventricular arrhythmias
- dose adjust in renal dysfunction: CrCl < 40 mL/min and hepatic dysfunction
- Substrate of 3A4
- TDM needed
- can induce heart failure b/c it’s a negative inotrope
- anticholinergic side effects
- on Beer’s list
- administer around the clock
21
Q
Quinidine
A
- Class IA
- Ventricular arrhythmias
- Atrial fibrillation / atrial flutter
- 3A4; eliminated by P-gp; inhibit 2D6; inhibit P-gp
- Dose adjust if CrCl < 10 mL/min
- Use with caution in hepatic impairment
- TDM
22
Q
Class IA pearls
A
- Use has fallen out of favor due to adverse effect risk outweighing antidysrhythmic benefits
- Notorious for QT-prolonging effects
- Avoid in patients with structural heart disease and/or CAD
23
Q
Disopyramide adverse effects
A
- Hypotension
- Exacerbate HF
- Xerostomia
- Constipation
- Urinary hesitancy
24
Q
Disopyramide patient counseling
A
take on empty stomach
25
Quinidine patient counseling
- Low Na diet & food can increase rate and extent absorption
- Fruit juice & vitamin C can increase clearance of quinidine
26
Quinidine contraindications
- Thrombocytopenia
- 2nd or 3rd degree heart block
- Concurrent use of quinolone antibiotics that prolong QT interval
27
Quinidine adverse effects
- GI distress
- Diarrhea
- Dizziness
- Fatigue
- Headache
- Palpitations
- Cinchoism
28
Procainamide dosing
- Loading Dose: 500-600 mg IV over 25-30 minutes
| - Maintenance Dose: 2-6 mg/min by continuous IV infusion
29
Quinidine dosing
- 267 mg of quinidine gluconate = 200 mg of quinidine sulfate
- Gluconate: ER: 648 mg PO q. 8 hours
- Sulfate: IR: 200-400 mg PO q. 6 hours ▪ ER: 300 mg PO q. 8-12 hours
30
Disopyramide
- Immediate release: 100-150 mg PO q. 6 hours
| - Controlled release: 200-300 mg PO q. 12 hours
31
Procainamide adverse effects
- hypotension (decrease dose)
- heart failure
- 1st degree AV block
- lupus erythematosus-like syndrome (long term = LT)
- blood dyscrasias (long term) ex. Agranulocytosis, Bone marrow suppression, Neutropenia, Thrombocytopenia
32
Class IB actions
- Mild inhibition of Phase 0
- shortens absolute refractory period
- shortens repolarization
33
Class IB pearls
- Used for treatment of ventricular arrhythmias (because works well on contractile cells)
- Use with caution in patients with hepatic disease and HF
- Relatively higher amount of CNS-related adverse effects
- Avoid in patients with structural heart disease and/or CAD
34
Lidocaine
- Xylocaine®
- VF or pulseless VT
- Hemodynamic monomorphic VT
- TDM
35
Mexiletine
- Ventricular arrhythmias
- must take every 8 hours to decrease variation in peaks and troughs; after dysrhythmia is controlled, could change interval to Q12h
- 1A2, 2D6 substrate
- Caution in patients with hepatic impairment and/or HF
36
Lidocaine doses
- 1 - 1.5 mg/kg bolus
- for VF or pulseless VT: 0.5 to 0.75 mg/kg bolus every 5 to 10 minutes (maximum cumulative dose: 3 mg/kg)
- Continuous infusion: 1 - 4 mg/minute
- Use lower dose in patients with hepatic dysfunction (metabolized by liver)
- 1A2, 3A4 substrate
37
Mexiletine doses
- 200-300 mg PO q. 8 hours
| - MDD of 1.2 grams
38
Lidocaine contraindications
- Premixed injection may contain corn-derived dextrose and its use is contraindicated in patients with allergy to corn or corn-related products
- Severe degrees of SA or AV block (except in patients with a functioning artificial pacemaker)
39
Mexiletine adverse effects
- GI effects limits people from tolerating this drug
- Gi: GI distress, N/V
- Dizziness
- Ataxia
- Hepatotoxicity
- Blood dyscrasias
- DRESS
40
Mexiletine patient counseling
- Take with food
| - Avoid diets or medications that increase urinary pH
41
Mexiletine patient counseling
- Take with food
- Avoid diets or medications that increase urinary pH
- do not recommend taking with antacid b/c if you make the urine basic, it doesn't allow medicine to be secreted in renal tubule
42
Class IC actions
- Major inhibition of Phase 0
- Minimal effect on absolute refractory period
- Minimal prolongation of repolarization
43
Class IC actions
- Major inhibition of Phase 0
- Minimal effect on absolute refractory period
- Minimal prolongation of repolarization
44
Class IC pearls
- Used primarily for supraventricular tachycardia
- Commonly prescribed in the outpatient setting
- Both agents have dietary considerations that effect plasma levels
- TDM is not commonly performed in practice
- Avoid in patients with structural heart disease and/or CAD
- used for Paroxysmal atrial fibrillation and Paroxysmal supraventricular tachycardia
45
Flecainide
- Tombocor®
- 2D6 substrate
- Caution in patients with hepatic dysfunction
- Dose adjust in patients with CrCl < 35 mL/min
46
Propafenone
- Rythmol®
- monitor CBC, LFT's, ECG
- Use with caution in patients receiving beta-blockers (b/c has BB activity)
- 2D6 substrate
- inhibits P-gp
- Dose adjust in hepatic dysfunction
47
Flecainide doses
- 50-100 mg PO q. 12 hours
| - MDD: 300-400 mg
48
Propafenone doses
- ER capsule: Initial 225 mg PO every 12 hours; May increase up to maximum of 425 mg every 12 hours
- IR tablet: Initial 150 mg PO every 8 hours; May increase up to maximum of 300 mg every 8 hours
49
Flecainide contraindications
- Ritonavir
| - Pre-existing 2nd or 3rd degree AV block
50
Flecainide counseling
- Clearance may be decreased in patients following strict vegetarian (via increase in urine pH)
- Milk may interfere with the absorption of flecainide
51
Flecainide adverse effects
- Dizziness
- Headache
- Fatigue
- Nausea
- Visual disturbances
- Dyspnea
52
Propafenone counseling
avoid grapefruit juice
53
Propafenone counseling
avoid grapefruit juice
54
Propafenone adverse effects
- Unusual taste
- Nausea
- Vomiting
- Dizziness
- Fatigue
- Blurred vision
55
Class II action
- Inhibit sympathetic influences on electrical activity
- Decrease SA/AV node automaticity & conduction velocity
- Increase action potential duration and effective refractory period
56
What are the beta blockers available for dysarrhythmia?
- Beta-adrenergic receptor antagonists with MSA: Propranolol, Metoprolol
- Beta-blockers without MSA are still commonly used in practice: Esmolol
57
Propranolol
- Inderal®
- Non-selective beta-blocker
- Can be used to treat arrhythmias caused by hyperthyroidism
- metabolized by 1A2, 2D6
58
Propranolol dosing
- 30-320 mg/day, divided every six to eight hours, orally (MDD of 640 mg)
- Can transition to extended-release formulation when dysrhythmia is controlled
59
Propranolol counseling
- Ethanol may increase or decrease plasma levels of propranolol
- High-protein diet can increase bioavailability
60
Esmolol
- Brevibloc®
- Advantageous when patients possess tenuous blood pressure/heart rate
- Metabolized by blood cell esterases.
- When transitioning to oral beta-blocker therapy, infusion should be reduced by 50% thirty minutes following the first dose of the alternative agent
61
Esmolol doses
- Continuous infusion
| - 500 mcg/kg/minute over 1 minute, then 50 mcg/kg/minute (max of 200 mcg/kg/minute)
62
Class III
- K channel blockers
| - prolong repol -> prolong QT interval
63
Which drugs are in the Class III?
- Amiodarone (Pacerone®, Cordarone®)
- Dronedarone (Multaq®)
- Ibutilide (Corvert®)
- Dofetilide (Tikosyn®)
- Sotalol (Betapace®, Betapace AF®)
64
Dronedarone brand name
Multaq®
65
Ibutilide brand name
Corvert®
66
Amiodarone
- Blocks all four Vaughan-Williams classifications (protects itself from having QT prolongation)
- Used to treat both atrial and ventricular arrhythmias
- metabolized by 2C8, 3A4
- inhibit P-gp, 2C9, 3A4
67
Amiodarone dose
- Oral: 200-1600 mg/day
| - IV: 150-300 mg rapid bolus, then 1 mg/minute for 6 hours, then 0.5 mg/min for 18 hours
68
Amiodarone adverse effects
- hypotension
- bradycardia
- thyroid dysfunction (hyper- and hypo-)
- N/V
- Acute and chronic liver impairment
- Skin photosensitivity
- Pulmonary toxicity: Pneumonitis, Fibrosis
- Peripheral neuropathy
- Optic neuritis
69
Amiodarone counseling
Avoid grapefruit juice
70
Amiodarone contraindications
- Hypersensitivity to iodine
- Second and third-degree AV block
- Cardiogenic shock
71
Sotalol
- Used to treat atrial and ventricular dysrhythmias
- as you increase the dose, you get more anti-arrhythmic effects
- Possesses predominantly non-selective beta-blocking properties at lower doses
- Get baseline QTc interval prior to initiation
- Frequency adjust in patients with CrCl ≤60 mL/min
- Can cause life threatening ventricular tachycardia associated with QT interval prolongation
- when dose started or changed, must be admitted to hospital for monitoring
72
Sotalol dosing
- Oral
| - 80-160 mg twice daily
73
Sotalol adverse effects
- Bradycardia
- Fatigue
- Dizziness
- Weakness
- Dyspnea
- Prolongation of QT-interval
74
Sotalol contraindications
Contraindicated if CrCl < 40 mL/min
75
Dofetilide
- Tikosyn
- Used to treat atrial fibrillation and atrial flutter
- Measure QTc before initiation
- Safe to use in patients with CAD or structural heart disease.
- Dose adjust in patients with CrCl < 60 mL/min
76
Dofetilide dosing
- Oral
| - 125-250 micrograms twice daily
77
Dofetilide adverse effects
- Headache
- Dizziness
- QT-prolongation
78
Dofetilide contraindications
- cimetidine
- dolutegravir
- hydrochlorothiazide
- itraconazole
- ketoconazole
- megestrol
- prochlorperazine
- trimethoprim
- verapamil
79
Class iV
- Non-Dihydropyridine Calcium Channel Antagonists
- Treat supraventricular dysrhythmias
- Atrial fibrillation/flutter
- Paroxysmal supraventricular tachycardia
80
Verapamil
- Calan®
- substrate of 3A4 and P-gp
- Moderate inhibitor of 3A4
- Inhibitor of P-gp
- May need to dose adjust in hepatic/renal impairment
- more GI effects compared to Diltiazem
81
Verapamil dosing
- IV
▪ 0.075 – 0.15 mg/kg bolus over 2 minutes
▪ 5 mg/hour CI
- Oral
▪ 240-480 mg daily in divided doses (three times daily), initially
▪ Transition to extended-release formulation
82
Diltiazem
- Dilacor®, Cardizem®
- substrate of 3A4 and P-gp
- Moderate inhibitor of 3A4
- Dose adjust in patients with liver impairment
83
Diltiazem dosing
```
- IV
▪ 0.25 mg/kg IV bolus over 2 minutes
▪ 5-10 mg/hour CI
▪ Avoid exceeding 15 mg/hour
- Oral
▪ Initially 30 mg q. 6 hours
▪ 120-360 mg/day in divided doses or extended-release formulation
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