LAB - 7.1 - Antiarryhtmic Agents Flashcards
The activation gates on the Na+ and K+ channels are closed, and the membrane’s resting potential is maintained.
Resting state
A stimulus opens the activation gates on some Na+ channels. Na+ influx through those channels depolarizes the membrane. If the depolarization reaches the threshold, it triggers an action potential.
Depolarization
Depolarization opens the activation gates on most Na* channels, while the K* channels’ activation gates remain closed. Na* influx makes the inside of the membrane positive with respect to the outside.
Rising phase of the action potential
The inactivation gates on most Na+ channels close, blocking Na* influx. The activation gates on most K+ channels open, permitting K+ efflux which again makes the inside of the cell negative.
Falling phase of the action potential
Both gates of the Na+ channels are closed, but the activation gates on some K+ channels are still open. As these gates close on most K+ channels, and the inactivation gates open on Na* channels, the membrane returns to its resting state.
Undershoot
is a problem with the rate or rhythm of your heartbeat.
Arrhythmia
it means that the heart beats too quickly, too slowly, or with an irregular pattern.
Arrhythmia
When the heart beats faster than normal, it is called .
tachycardia
When the heart beats too slowly, it is called .
bradycardia
The most common type of arrhythmia is ___, which causes an irregular and fast heart beat.
atrial fibrillation
Electrical changes associated with atrial depolarization
P wave
Electrical changes associated with ventricular depolarization
QRS complex
Electrical changes associated with ventricular repolarization
T wave
The electrical changes associated with atrial repolarization normally coincide with the ___ complex and are obscured by it.
QRS
___ drugs affect the action potential of the cardiac cells, altering their automaticity, conductivity, or both
Antiarrhythmic
Can Anti-arrhytmic drugs cause arryhytmia?
YES
Classification of Antiarrhythmics (Based on Mechanisms of Action)
Class I – Blocker’s of Fast Na+ Channels
Which Class I Sublass features:
Prolong repolarization
Increased duration of action potential
Subclass IA
Examples of Subclass IA Medications
Quinidine
Procainamide
Disopyramide
Class I Antiarryhtmic Drugs are ___ blockers
Sodium
Which Class I Sublass features:
Shortened depolarization
Decreased action potential duration
Subclass IB
Examples of Subclass IB Medications
Lidocaine
Mexiletine
Phenytoin
This Subclass IB Medication is approved only for use in life-threatening ventricular arrhythmias in adults
Mexiletine
Which Class I Sublass features:
No effect of depolarization and on action potential duration
Subclass IC
Examples of Subclass IC Medications
Flecainide
Propafenone
This Subclass IC Medication was initially developed as a local anesthetic. It slows conduction in all parts of heart
Flecainide (Tambocor)
This Subclass IC Medication:
- Also slows conduction
-Weak β – blocker
Propafenone
affect predominantly slow-channel tissues (sinoatrial [SA] and atrioventricular [AV] nodes), where they decrease rate of automaticity, slow conduction velocity, and prolong refractoriness
Class II – β–adrenergic blockers
Examples of Class II – β–adrenergic blockers
Propranolol
Metoprolol
Atenolol
Pindolol
This Class II – β–adrenergic blocker:
Slows SA node and ectopic pacemaking
Can block arrhythmias induced by exercise or apprehension
Other β–adrenergic blockers have similar therapeutic effect:
Propranolol
Block potassium channels and slow the outward movement of potassium during phase 3 of the action potential, thereby prolonging it
Class III – K+ channel blockers
Developed because some patients are sensitive to Na channel blockers (they died!)
Class III – K+ channel blockers
Examples of Class III – K+ channel blockers
Amiodarone
Bretylium
Dofetilide
Sotalol
This Class III – K+ channel blocker is the drug of choice for treating ventricular fibrillation or pulse less ventricular tachycardia in cardiac arrest situations
Amiodarone
Block the movement of calcium ions across the cell membrane thereby decreasing the excitability and contractility of the myocardium
Slow the rate of AV-conduction in patients with atrial fibrillation
Class IV – Ca+ Channel Blockers
Examples of Class IV – Ca+ Channel Blockers
Verapamil
Diltiazem
This Class IV – Ca+ Channel Blocker blocks Na+ channels in addition to Ca2+, also slows SA node in tachycardia
Verapamil (Isoptin)
There is a risk of severe cardiac effects if Class IV drugs are given IV within ___ hours of IV beta-adrenergic drugs. The combination should be avoided.
48
Nursing Implementation for Antiarryhtmic Agents
Titrate the dose to the smallest amount needed to achieve control of the arrhythmia to decrease the risk of severe adverse effects.
Continually monitor cardiac rhythm when initiating or changing dose to detect potentially serious adverse effects and to evaluate drug effectiveness.
Ensure that emergency life support equipment is readily available to treat severe adverse reactions that might occur.
Administer parenteral forms as ordered only if the oral form is not feasible; expect to switch to the oral form as soon as possible to decrease the potential for severe adverse effects.
Consult with the prescriber to reduce the dose in patients with renal or hepatic dysfunction; reduced dose may be needed to ensure therapeutic effects without increased risk of toxic effects.
Establish safety precautions, including side rails, lighting, and noise control, if CNS effects occur to ensure patient safety.
Arrange for periodic monitoring of cardiac rhythm when the patient is receiving long-term therapy to evaluate effects on cardiac status.
