Arrhythmia Drugs

Question 1

What are the 2 mechanisms of arrhythmias?

Answer 1

Increased Automaticity

Re-entryZ

Question 2

Name the classes of Anti-Arrhythmic Drugs

Answer 2

Class1 - Na+ channel blockers
Class 2- B-blockers
Class 3 - K+ channel blockers
Class 4- Ca2+ channel blockers
Class 5 - Adenosine receptor agonists (Adenosine)
Class 6 - Digoxin?

Question 3

QT prolongation puts you at risk for what arrhythmia?

Answer 3

Polymorphic Ventricular Tachycardia (TORSADES de POINTE)

an early afterpolarization

Question 4

Name the 3 mechanisms of increased automaticity.

Answer 4

1. Enhanced Normal Automaticity: Rapid firing of normal pacemaker cells
2. Abnormal - spontaneous depolarization of myocytes without pacemaker current
3. Triggered Automaticity - caused by preceding depolarization

QT prolongation causes them. Early or late afterdepolarizations.

Question 5

How do you treat enhanced NORMAL automaticity?

Answer 5

Enhanced normal automaticity just means your normal pacemakers are too excitable. To tone them down, you need to: (here are options)

1. Decrease Phase 4 slope via Ca2+ channel blockers (verapamil, diltiazem)
2. Increase parasympathetic activity (Adenosine) or vagal tone (carotid massage)

Question 6

How do you treat enhanced ABNORMAL automaticity? (and what is it anyway….)

Answer 6

Enhanced Abnormal Automaticity is the spontaneous depolarization of atrial or ventricular myocytes without signal from the Pacemaker.

4 ways to treat it:

1. Decrease Phase 4 slope –> B-blockers: decreased sympathetic tone causes decreased heart rate, contractility, and automaticity.
2. Increase the threshold potential for depolarization via Na+ channel blockers. (Procainimide Class 1A, Flecanide Class 1C)
3. Hyperpolarize the cells via Na+ channel blockers
4. Increase the AP duration (K+ channel blockers)

Question 7

Which Na+ channel blocker has specificity for injured, ischemic tissues, with little affinity for functional myocytes?

Answer 7

Class 1B–> Lidocaine

Groups 1A (Procainimide) and 1C (Flecanide) have affinity for Na+ channels on all myocytes, regardless of functional status.

Still, they ALL target active Na+ channels, so they have greater affinity for cells depolarizing at a rapid, more frequent rate. (the abnormal ones!)