MT3I: ANTIARRHYTHMIC AND ANTIANGINAL

• Arrhythmia- is a problem with the rate or rhythm of the heartbeat. It involves a change to the automaticity and conductivity of the heart cells.
• Are factors that can lead to the changes of action potential:

  • electrolyte imbalance
  • decreased oxygen delivery to cells
  • acidosis and waste product accumulation
  • changes on the damaged structures
• In Arrhythmia, the heart beats either too quickly, slowly, or with an irregular pattern.
• Atrial Fibrillation- is the most common type of arrhythmia causing an irregular and fast heartbeat.
• What are the conduction systems:

  • P wave - atrial depolarization
  • QRS complex - ventricular depolarization
  • T wave - ventricular repolarization
• Approximate values for normal intervals:

  • PQ (PR) interval - 0.16 secs
  • OT interval - 0.3 secs
  • QRS interval - 0.08 secs
  • P wave - 0.08 secs
  • ST interval - 0.1 secs
• Anti-arrhythmic drugs


  affects the action potential of cardiac cells, altering their automaticity, conductivity, or both.
• The effect of anti-arrhythmic drugs may cause to produce new arrhythmias-a condition called "Proarrhythmia"
• When prescribing anti--arrhythmia medications, the nurse must be very vigilant on the dosage, blood levels, and follow ups.
• Anti-arrhythmia medications are classified based on their mechanism of action:

  • Class I - Fast Na channel blockers
  • Class II - B adrenergic blockers
  • Class III - K channel blockers
  • Class IV - Calcium channel blockers
• Class I: Fast sodium channel blockers 


  are drugs that blocks sodium channels in the cell membrane during an action potential.
• Class I AAs are subdivided into three categories:

  • Subclass IA - prolongs repolarization leading to increased action potential duration.
• Drugs under subclass IA:

  • Quinidine
  • Procainamide
  • Disopyramide
• Quinidine 


  is the first antiarrhythmic medication used to treat both Atrial and Ventricular arrhythmias.
• Procainamide and Disopyramide 


  treatment for life-threatening ventricular arrhythmias
• Subclass IB


  shortens depolarization and decreases action potential duration
• Drugs from Subclass IB:

  • Lidocaine
  • Mexiletine
  • Phenytoin
• lidocaine (Local Anesthetic) - is good for digitalis associated arrhythmias and is used in life threatening ventricular arrhythmia during myocardial infarction or cardiac surgery.
• Lidocaine - is also used as bolus injection in emergency cases
• Mexiletine - is approved only in ventricular arrhythmias in adults
• Subclass IC


  Has now effect on depolarization and action potential duration
• Drugs under Subclass IC:

  • Flecainide (Tambocor)
  • Propafenone
• Flecainide - is initially developed as "local anesthetic" and slows the conduction of all heart parts
• Propafenone - slows conduction and is a weak B blocker
• Class II- B adrenergic blockers 


  blocks beta receptors in the heart and kidneys slowing down the AV node conduction and decreases the release of renin.
• The action of beta-adrenergic blockers leads to:

  • decreased heart rate
  • decreased cardiac excitability
  • decreased cardiac output
• Class II - Beta adrenergic blockers 


  helps stabilize cardiac rhythm
• Drugs under Class II- Beta adrenergic:

  • Propranolol (Inderal)
  • Metoprolol (Betaloc, Cardiosel, Neobloc)
  • Atenolol (Tenormin, Therabloc)
  • Pendolol (Visken)
• Propranolol - slows the SA node and ectopic pace making. It also blocks arrhythmias induced by exercise or apprehension.
• Class III- K channel blockers 


  blocks potassium channels slowing the outward movement of potassium during phase 3 which prolong action potential.
• Class III- K potassium channel


  are developed because some patients are sensitive to NA channel blockers
• Drugs under Class III- K channel blockers:

  • Amiodarone
  • Dofetilide
  • Sotala
  • Bretylium
• Amiodarone - is a drug of choice for treating ventricular fibrillation or pulse less ventricular tachycardia in cardiac arrest solutions.
• Dofetilide - maintenance of normal sinus rhythm
• Sotala - treatment for ventricular arrhythmia in adults, esp those who are unresponsive to other drugs.
• Sotala - maintenance of sinus rhythm to patients with AF or Atrial Flutter
• Class IV- Calcium Channel Blockers 


  blocks the movement of calcium ions across cell membrane which decreases excitability and contractility of myocardium.
• Class IV- Calcium channel blockers 


  slows the rate of AV conduction to patients with Atrial Fibrillation
• Drugs under Class IV- Calcium channel blockers:

  • Verapamil (Isoptin)
  • Diltiazem (Dilzem)
• Verapamil - blocks Na channel, aside from Ca channel, and slows down SA node in tachycardia.