(2) CV & Renal: Antiarrhythmics (4.1-4.5) Flashcards
MOA: Class I antiarrhythmics
Block Na+ channels
(and ∴ ↓ Rate of rise of AP)
Class I antiarrhythmics readily bind to Na+ channels in what state?
Open or inactivated
(Not resting)
Are type I antiarrhythmics use-dependent or use-independent?
Use-dependent
What effect do class I antiarrhythmics have on SA and AV node?
None
What effect do class I antiarrhythmics have on EKG tracing?
Widened QRS complex
What are the class IA antiarrhythmics?
“Double Quarter Pounder”
(1) Disopyramide
(2) Quinidine
(3) Procainamide
What are the class IB antiarrhythmics?
“Lettuce, Pickles, Mustard”
(1) Lidocaine
(2) Phenytoin
(3) Mexilitine
What are the class IC antiarrhythmics?
“Extra fries, please!”
(1) Encainide
(2) Flecainide
(3) Propafenone
Rank the class I antiarrhythmics in regards to Na+ channel affinity
Think: “CAB”
- Highest: Class IC
- Intermediate: Class IA
- Lowest: Class IB
Other than affecting Na+ channels, what is the MOA of class IA antiarrhythmics?
Inhibit K+ channels
What region of the heart is each division of class I antiarrhythmics selective for?
- Class IA: Supraventricular and ventricular
- Class IB: Ventricles and Purkinje system
- Class IC: Supraventricular and ventricular
What class of antiarrhythmic is used to treat Wolff-Parkinson-White syndrome?
Class IA
Adverse Effects (3) : Quinidine
(1) Cinchonism
(2) Thrombocytopenia
(3) Torsades
* (Remember all class IA can cause Torsade de Pointes)*
Which Class I antiarrhythmic is a negative inotrope?
Disopyramide
(*Remember all class IA can cause Torsade de Pointes)
Which division of class I antiarrhythmics can cause Torsades de Pointes?
Class IA
Which division of class I antiarrhythmics are used for ischemia-induced ventricular arrhythmias?
Class IB
Adverse Effect: Class IB antiarrhythmics
Neurological side effects
Distinguish class IA, IB, and IC antiarrhythmics by their effect on action potential duration
- Class IC: No affect
- Class IB: Shorten AP
- Class IA: Prolongs AP
Which division of class I antiarrhythmics are used to treat atrial fibrillation?
Class IC
Contraindication: Class IC antiarrhythmics
(1) Structural heart disease
(2) Ischemic heart disease
* (≅ Preexisting heart disease)*
Which class I antiarrhythmic is a negative inotrope?
Disopyramide
Which antiarrhythmic can cause a lupus-like syndrome?
Procainamide
What are the class II antiarrhythmics?
β-blockers
What is the mechanism of β-blocker treatment of arrhythmias?
Prolongs nodal Φ4
(Via reducing sympathetic input to SA/AV node)
What part of the heart do class II antiarrhythmics most affect?
AV node
(Although they do affect SA too)
What type of arrhythmias do class II antiarrhythmics treat?
Supraventricular
(i.e., atrial fibrillation)
Name a class II antiarrhythmic that can be used for acute supraventricular arrhythmia
Esmolol
(∵ IV administration)
What effect do class II antiarrhythmics have on EKG tracing?
Prolonged PR interval
What are the class III antiarrhythmics?
(1) Amiodarone
(2) “-tilide”
(3) Sotalol
MOA: Class III antiarrhythmics
Inhibit cardiac K+ channels
What phase of cardiac action potential is affected by class III antiarrhythmics?
Phase 2 and 3
What class III antiarrhythmic shares mechanistic features of class I-IV drugs?
Amiodarone
What β-blocker is a class III antiarrhythmic?
Sotalol
What type of arrhythmias can class III antiarrhythmics treat?
Supraventricular and ventricular
Adverse Effects (9) : Amiodarone
(1) Neurological side effects
(2) Gray corneal deposits
(3) Hypo/Hyperthyroidism
(4) Pulmonary fibrosis
(5) Heart block
(6) Induce heart failure
(7) Hypersensitivity hepatitis
(8) Gray-blue skin discoloration
(9) Photodermatitis
Which antiarrhythmic inhibits CYP-450?
Amiodarone
Which class III antiarrhythmic has the lowest incidence of Torsades de Pointes?
Amiorodone
Generally, what is the difference in mechanism between class II/IV antiarrhythmics and class I/III?
- Class II/IV: Rate control
- Class I/III: Rhythm control
Which antiarrhythmic agents do not fall into class I-IV designation?
(1) Digoxin
(2) Mg2+
(3) K+
(4) Adenosine
MOA: Digoxin treating atrial fibrillation
↑ Parasympathetic effects
What type of arrhythmia does Mg2+ treat?
Torsades de pointes
What changes on EKG tracing will be present in hyperkalemia?
Peaked T waves
(With shortened QT interval)
What changes on EKG tracing will be present in hypokalemia?
U wave
(At the end of T wave)
What receptor does Adenosine stimulate to ↓ SA/AV node activity?
A1
What effect does the stimulation of A1 receptor have on the cardiac ion currents?
(1) ↑ Outward K+ current
(2) ↓ Inward Ca2+ current
* (Both factors inhibit AP)*
Where in the heart does Adenosine exert most of its effects?
AV node
What type of arrhythmia is Adenosine a first-line treatment for?
Supraventricular
What effect does the stimulation of coronary A2 receptors have?
Vasodilation
Adverse Effects (3) : Adenosine
(1) Cutaneous flushing
(2) Shortness of breath/Chest pain
(3) Hypotension
What class of drugs inhibits the cardiac effects of Adenosine?
Methylxanthines
(Caffeine, Theophylline)
