Class 1A/1B/1C Antiarrhythmic Drugs Flashcards

Questions and Answers

What is the phase 0 cardiac action potential upstroke caused by?

Potassium

Magnesium

Sodium (correct)

Calcium

Which of the following correctly describes phase 2 of cardiac action potentials?

Plateau via Ca2+ (correct)

Na+ channel blocking

Phase 0 upstroke

Repolarization by K+

What do class 1 antiarrhythmics primarily block?

Sodium channels

How do class 1 antiarrhythmics affect the slope of the phase 0 upstroke?

They decrease the slope. Signup and view all the answers

What is the effect of 'use dependence' in class 1 antiarrhythmics?

Greater effect on rapidly depolarizing tissues Signup and view all the answers

What current is present in phase 2 and phase 3 of the action potential?

K+ current Signup and view all the answers

Class 1 antiarrhythmics affect the SA and AV nodes.

False Signup and view all the answers

What effect do class 1 antiarrhythmics have on the QRS complex?

Widen the QRS complex. Signup and view all the answers

Which of the following is a Class 1A antiarrhythmic?

Disopyramide Signup and view all the answers

What syndrome can quinidine toxicity cause?

Cinchonism Signup and view all the answers

Class 1B antiarrhythmics are primarily used to treat __________ arrhythmias.

Ventricular Signup and view all the answers

What adverse effects are associated with class 1B antiarrhythmics?

Neurological side effects including paresthesias, tremors, and convulsions. Signup and view all the answers

Match the following Class 1 antiarrhythmics with their respective subclasses:

Lidocaine = Class 1B Mexiletine = Class 1B Flecainide = Class 1C Propafenone = Class 1C Signup and view all the answers

Study Notes

Cardiac Action Potentials

Phase 0: Upstroke of cardiac AP is driven by Na+ influx.
Phase 2: Plateau phase maintained by Ca2+ currents.
Phase 3: Repolarization occurs via K+ outflow.

Class 1 Antiarrhythmics

Block sodium channels, impacting phase 0 upstroke and conduction velocity.
Category 1A drugs (quinidine, procainamide, disopyramide) slow the conduction of cardiac action potentials.
Class 1A drugs also block K+ channels, prolonging phases 2 and 3, which extends the refractory period.

Use-Dependence

Class 1 antiarrhythmics have greater effects on rapidly depolarizing tissues; higher heart rates can lead to slower phase 0 upstrokes.

Pharmacological Classes

Class 1A: Intermediate sodium channel binding strength; effective in atrial and ventricular arrhythmias.
Class 1B: Low affinity for Na+ channels, effective primarily in ventricular arrhythmias, especially in ischemic tissue.
Class 1C: Strongest sodium channel binding, used for atrial fibrillation and flutter.

Specific Drug Effects

Quinidine: Potentially causes cinchonism (tinnitus, headache, dizziness) and thrombocytopenia.
Procainamide: Long-term use can trigger lupus-like syndrome.
Disopyramide: Negative inotropic effects may worsen heart failure.
Lidocaine and Mexiletine (Class 1B) known for neurological side effects like paresthesias and tremors.

Cardiac Implications

Class 1A agents increase QT interval, risk of torsades de pointes due to prolonged action potential duration.
Class 1C drugs do not affect AP duration, but strongly inhibit Na+ channels, associated with widest QRS complex during dysrhythmias.

Contraindications

Class 1C antiarrhythmics contraindicated in patients with structural or ischemic heart disease due to potential proarrhythmic effects.

Description

Test your knowledge on antiarrhythmic drugs with these engaging flashcards designed for Class 1A, 1B, and 1C. Each card contains key concepts related to cardiac action potentials and the mechanisms of these medications. Perfect for quick revision and memorization!