Anti-arrhythmics Flashcards
Drugs that ↓ firing rate of pacemakers:
-CCB: ↑phase 0 threshold\
-NaCB: ↓phase 4 slope
-BetaB:
↓phase 4 slope
↑phase 0 threshold
↑action potential duration
↑maximum diastolic potential
Drugs that ↓ conduction velocity through the AVN:
-CCB: slow impulse propagation
-BetaB
Drugs that ↓ conduction velocity through the atria & ventricles:
-NaCB: slow impulse propagation
Drugs that ↑ refractory period:
-KCB
-CCB
-BetaB
K channel blockers
Increase QT directly without affecting heart rate
↑QT ↔ RR ↑QTc
Beta blockers & Ca channel blockers
Increase QT indirectly by slowing heart rate ↑QT ↑RR ↔ QTc
Arrhythmias: Classification
Arrhythmias: Treatment strategies
Effects of Antiarrhythmic Drugs
Antiarrhythmic drugs have a _____ therapeutic index
narrow
Rate vs Rhythm Control
Beta Blockers and Ca Channel Blockers: Properties
Sodium Channel Blockers: Classes
Class IA sodium channel blockers
MOA:
– Moderate binding to Na channels = ↑QRS interval
– Also block K channels = ↑action potential duration (APD)
– Also block ACh = anti-cholinergic effects
Class IB sodium channel blockers
MOA:
– Weak binding to Na channels = ↔ QRS interval
– ↓action potential duration (APD)
Uses:
– Ventricular arrhythmias only
Class IC sodium channel blockers
MOA:
– Strong binding to Na channels = ↑↑↑ QRS interval
– ↔ action potential duration (APD)
– May also ↑PR interval, ↓contractility
Uses:
– Ventricular & supraventricular arrhythmias
– Most common = AF/AFL
– Increased mortality in patients with CHF and CAD
Pneumonic for NaCB Classes
Potassium Channel Blockers
- MOA:
– ↑APD, refractoriness - Most important thing to remember:
– ↑QTc = risk of Torsades de Pointes
Importance of Rate Control
Amiodarone
Digoxin
Adenosine
- “Class V” antiarrhythmic drug
- Uses:
– Acute treatment of PSVT
– Diagnostically as a coronary vasodilator
– IV only
MOA
– Binds adenosine A1 receptors in SAN/AVN
* SAN: ↓ Firing rate
* AVN: ↓↓↓↓ Conduction velocity
Effect
– When given as a fast IV bolus, halts AVN conduction
Clinical Impact: K and NA Blockers
