Anti Arrythmic Flashcards
(24 cards)
What is the resting membrane potential of a normal cardiac cell?
-90 mV
This value represents the electrical charge difference across the cell membrane when the cell is at rest.
What causes depolarization in cardiac cells?
Due to Na+ entry through Na+ channels
Depolarization is the process that makes the inside of the cell more positive.
What leads to hyperpolarization in cardiac cells?
Due to K+ exit through K+ channels at resting state
Hyperpolarization makes the inside of the cell more negative.
What is the mechanism behind repolarization in cardiac action potentials?
Due to K+ exit through K+ channels at depolarization state
Repolarization restores the resting membrane potential after depolarization.
What is the peak value of an action potential in cardiac cells?
+30 mV
This value indicates the maximum electrical charge achieved during an action potential.
What is the effect of Na channel blockers on Phase 0 of the action potential?
They act by decreasing the slope [dV/dt] of Phase 0
This action slows the rate of depolarization.
What is the effect of K+ channel blockers on action potential duration?
They prolong action potential duration [APD] and increase QT interval in ECG
Prolonged QT interval can lead to Torsades de pointes (TDP).
What is the effect of K+ channel openers on action potential duration?
They decrease action potential duration [APD]
This can lead to a more rapid recovery of the cardiac cell’s resting state.
What classification system is used for anti-arrhythmic drugs?
Vaughan Williams Classification
This classification is based on the predominant mechanism of action of the drugs.
What type of channel blockers are classified as Class I anti-arrhythmic drugs?
Na+ Channel Blockers
These drugs primarily act on sodium channels to affect cardiac excitability.
What are the classes of anti-arrhythmic drugs?
Class I, Class II, Class III, Class IV, Class V
Class I includes Na+ channel blockers, Class II includes beta blockers, Class III includes K+ channel blockers, Class IV includes Ca2+ channel blockers, and Class V includes others.
What is the primary action of Class I anti-arrhythmic drugs?
Na+ channel blockers
Class I drugs block sodium channels affecting the slope of Phase 0.
What are the subclasses of Class I anti-arrhythmic drugs?
1a, 1b, 1c
Each subclass has different effects on potassium channels.
What is the effect of Class 1a drugs?
Block K+ channels, precipitating TDP
TDP refers to Torsades de Pointes, a type of life-threatening arrhythmia.
Name two examples of Class 1a drugs.
Quinidine, Procainamide
These drugs can cause QT prolongation.
What is the primary use of Class 1b drugs?
Used only for ventricular arrhythmia
Lignocaine is the drug of choice for digoxin-induced ventricular arrhythmias.
Name an example of a Class 1b drug.
Lignocaine
Phenytoin and Tocainide are also included in this class.
What is the primary use of Class 1c drugs?
Used for WPW syndrome
The treatment of choice for WPW syndrome is radiofrequency ablation of the aberrant pathway.
Name two examples of Class 1c drugs.
Encainide, Flecainide
These drugs have specific applications in arrhythmias associated with WPW syndrome.
What are the primary actions of Class II anti-arrhythmic drugs?
Beta blockers
These drugs are primarily used in tachyarrhythmias.
What is the main action of Class III anti-arrhythmic drugs?
K+ channel blockers
They play a crucial role in the management of various arrhythmias.
Name two examples of Class III drugs.
Dofetilide, Dronedarone
Amiodarone and Sotalol are also included in this class.
What is unique about Sotalol?
Has both Class III and Class II actions
It combines properties of potassium channel blocking and beta-blocking.
What is notable about Amiodarone?
Longest acting anti-arrhythmic drug (t1/2 > 3 weeks)
It has multiple mechanisms of action including Na+ channel blocking and non-competitive beta-blocking.
