Antiarrhythmics 3 Flashcards
Effects of which class of drugs?
- Prolong the AP duration by reducing the outward (repolarizing) phase 3 potassium current
- ***Main effect is to prolong the effective refractory period (ERP)
- Note - phase 4 diastolic potassium current (IK1) is not affected by these drugs.
class 3
Which drug’s MOA:
- Blocks IKr, INa, ICa-L channels,
- β adrenoceptors
Amiodarone
Effects of which drug?
- **Prolongs action potential duration and QT interval
- slows HR and AV node conduction
- low incidence of torsades de pointes
Amiodarone (class 3)
What are the clinical applications of Amiodarone (class 3)
1.** Serious ventricular Arrhythmias
2. **Supraventricular arrhythmias
What is the most commonly prescribed AAD?
Amiodarone (Class 3)
Pharmacokinetic of which drug?
- Oral, IV
- variable absorption and tissue accumulation
- hepatic metabolism, elimination complex and slow
Amiodarone (class 3)
Which drug has the following toxicities?
- Bradycardia and heart block in diseased heart,
- peripheral vasodilation
- **pulmonary fibrosis
- hepatic toxicity
- **hyper- or hypothyroidism
Amiodarone (class 3)
Which drug has many interactions, based on CYP metabolism
Amiodarone (class 3)
The impressive effectiveness of ________ coupled with its low proarrhythmic potential has challenged the notion that selective ion channel blockade by AADs is preferable
Amiodarone
What is the MOA of Dofetillide (class 3)?
IKr block
What are the 2 effects of Dofetillide (class 3)?
- prolongs action potential
- Prolongs effective refractory period
Clinical application of which med?
Maintenance or restoration of sinus rhythm in A-fib
Dofetillide (group 3)
PK of which drug?
Oral
• renal excretion
Dofetillide (class 3)
What is the toxicity of Dofetillide (class 3)?
***Torsades de pointes
(initiate in hospital)
Interaction of which class 3 med?
Additive with other QT-prolonging drugs
Dofetillide
Which class 3 med is used for ventricular arrhythmias and A-fib?
Sotalol
Which class 3 med is used for conversion of atrial flutter and A-fib?
Ibutillide
Which class 3 drug reduces mortality in patients with A-fib?
Dronedarone
Which drug prolongs atrial refractoriness and is effective in A-fib
Vernakalant
Effects of which class of drugs?)
•**Reduce inward calcium current during the AP and during phase 4
•**Result= conduction velocity is slowed in the AV node and refractoriness is prolonged
•Pacemaker depolarization is slowed during this phase as well if caused by excessive calcium current.
Class 4
Ca2+ channel blockers (L-Type) decrease excitability of SA nodal cells and prolong AV nodal conduction, primarily by slowing the ______ upstroke in nodal tissue.
actional potential
Which class of meds are useful in tx of arrhythmias that involve re-entry through the AV node
Class 4
High doses of Ca2+ channel blockers can prolong AV nodal conduction to such an extent that______ results
heart block
MOA of which 2 drugs?
- **Dependent ICa block slows conduction in AV node and pacemaker activity
- PR interval prolongation
Verapamil
Diltiazem
What is the clinical application of Verapamil?
**AV nodal arrhythmias, especially in prophylaxis
What is the clinical application of diltiazem (class 4-CCB)?
**Rate control in A-fib**
Which 2 meds have the following toxicities:
- Cardiac depression
2. **Constipation
3. **Hypotension
Verapamil and diltiazem (class 4- CCB)
Which group of meds are calcium channel blockers but are not useful in arrhythmias; sometimes precipitate them
Dihydropyridines (group 4- CCBs)
MOA of which drug?
**interacts with Na+/K+-ATPase, K+, and Ca2+ channels**
(poorly understood)
Magnesium
which drug normalizes or increases plasma Mg?
Magnesium
Which drug has the following clinical application:
**Torsades de pointes
**Digitalis-induced arrhythmias
Magnesium
Pharmacokinetics of which med?
IV
• duration dependent on dosage
Magnesium
What is the toxicity of Magnesium?
Muscle weakness in overdose
Which med increases K+ permeability, K+ currents**
Potassium
What are 2 effects of potassium?
- Slows ectopic pacemakers
- slows conduction velocity in heart
What are the 2 clinical applications of Potassium?
- Digitalis-induced arrhythmias
- **arrhythmias associated with hypokalemia
what 2 toxicities can occur with potassium in the tx of arrhythmias?
1. **Reentrant arrhythmias
2. **Fibrillation or arrest in overdose
MOA of which drug?
- **Activates inward rectifier IK
- **blocks ICa
Adenosine
What is the effect of Adenosine?
Very brief, usually complete AV blockade
What is the clinical application of Adenosine?
**Paroxysmal supraventricular tachycardias (PSVTs)**
(stops heart with hopes it will reset at normal rhythm)
Which med?
**IV only–> duration 10-15 seconds**
Adenosine
What are the 3 toxicities of Adenosine?
1. **Flushing
2. **Chest tightness
3. **Dizziness
In patients with A-fib, therapy is traditionally aimed at what 3 things?
- Controlling ventricular rate
- Preventing thromboembolic complications
- Restoring and maintaining sinus rhythm
In patients with A-fib, what 4 meds are used to control ventricular rate?
- Digoxin
- Nondihydropyridines
- CCBs
- Beta Blockers
In patients with A-fib, what 2 meds are used to prevent thromboembolic complications
- Warfarin
- Aspirin
In patients with A-fib, what 2 meds are used to restore and maintain sinus rhythm?
- AADs
- Direct-current cardioversion (DCC)
What have studies shown about tx of A-fib?
- no need to try to maintain SR
- Rate control alone is often good enough
- Chronic AAD therapy may still be needed in pts who continue to have sxs despite good rate control
T/F: the use of antiarrhythmic drugs in the US has declined
TRUE because:
- some trials show increased mortality w/ AADs
- Proarrhythmia is a significant side effect
- Advances in technology such as- Ablations and ICDs
What technologies are now being used to tx arrhythmias instead of antiarrhythmic drugs?
ICD (reduced mortality in EF<30%)
radiofrequency catheter ablation or cryoablation (for arrhythmias w/ defined anatomic pathways)
