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1

Class 1A

Mechanism: What channels are blocked? Where is conduction velocity slowed?

How does this affect action potential duration (APD) and effective refractory period (ERP)?

Class 1A

Mechanism: block fast Na chnls --> slow conduction velocity @ atria, Purkinje, ventricles

APD, ERP: both increased

2

There are three Class 1A drugs.

Which drug has cinchoism, cardiac depression, reduced Digoxin clearance, Torsades, and upset GI as side effects?

Which drug causes hypotension and lupus-like side effects?

What is the last one?

Class 1A drugs are used to treat what types of arrhythmias?

Class 1A

1) Quinindine
--cinchoism, cardiac depression, reduced Digoxin clearance, Torsades, upset GI

2) Procainamide
--hypotension, lupus

3) Disopyramide

Tx: atrial & ventricular arrhythmias

3

Class 1B

Mechanism:
What channels are blocked?
In what type of tissue? At what location?
How are APD and ERP affected?

Class 1B

Block fast Na chnls, especially in inactivated state

@ ischemic/depolarized tissue of Purkinje & ventricle

decreased APD, but prolonged ERP due to slower recovery of Na chnls from inactivation

4

There are two Class 1B drugs.

Which one is used to treat both acute ischemic arrhythmia post-MI and Digoxin toxicity? How is this drug administered?

Which drug is the oral formulation of the first drug?

Lidocaine
--Tx: acute ischemic arrhythmia post MI; Dig tox
--Admin: IV only due to high first-pass effect and toxic metabolites

Mexiletine
--Oral formulation of Lidocaine

5

What are two important side effects of Lidocaine?

seizures/neuro; CV depression

6

Class 1C

Mechanism
What channels are blocked?
At what location?
How is APD affected?

Class 1C

Block fast Na chnls
@ His-Purkinje
no effect on APD

7

There are two Class 1C drugs.

Which one is used to treat refractory VT and refractory SVT?

The second drug is similar, but has an active metabolite.

Flecainide
--refractory VT, refractory SVT

Propafenone
--has active metabolites

8

Class 1C drugs

How do they rank in terms of potency of Na chnl blocking?

What is a contraindication, due to side effects of worsened HF, depressed LV function, and proarrhythmia?

Most potent Na chnl blockers

Contraindication: structurally abnormal hearts

9

Class 2 Drugs: Beta Blockers

Mechanism: beta receptor blockade...
--> Increase or decrease cAMP?
--> Which currents are suppressed?
--> Abnormal pacemakers in which tissue are especially sensitive?

Class 2 Drugs: Beta Blockers

Mechanism: beta receptor blockade...
--> decrease cAMP
--> reduced Na, Ca currents
--> suppress abnormal pacemakers in AV node

10

Class 2 Drugs: Beta Blockers

List the three beta blockers used.

What are its two main arrhythmia-related therapeutic uses?

1) Metoprolol
2) Atenolol
3) Nadolol

Therapy:
1) post-MI prophylaxis
2) SVT

11

Class 3 Drugs

Mechanism
What channels are blocked?
What current is affected?
What is the effect on APD and ERP?

Class 3 Drugs

Mechanism
Block K chnls
--> reduce repolarizing current (phase 3)
--> prolong APD & ERP

12

There are five Class 3 drugs.

Which one can be used to treat almost any arrhythmia, but has many iodine-related side effects like pulmonary fibrosis, blue pigmentation, and corneal deposits?

Which one is a less efficacious, less toxic version of the same drug, that can be used to treat A-Fib and A-Flutter?

Amiodarone
--very efficacious
--iodine related toxicity

Dronedarone
--less efficacious, less toxic version of Amiodarone

13

There are five Class 3 drugs.

Which Class 3 drug has beta blocking effects in addition to its K chnl blocking property? What type of arrhythmia is it used to treat? What is an important side effect?

Sotalol
--beta blocking effects
--Tx: ventricular arrhythmia
--Side effect: Torsades

14

There are five Class 3 drugs.

Three of them are Amiodarone, Dronedarone, and Sotalol.

Of the other two, which one is highly selective for atrial tissue and can cause Torsades?

What is the last one?

Dofetilide
--atrial selective
--Torsades

Ibutilide

15

Class 4 Drugs

Mechanism
What current is blocked, and during what phases?
At what locations?

What are the two Class 4 drugs? Which one is given IV?

Class 4 Drugs

Mechanism
--block inward Ca current
--Phases 0 & 4
--SAN, AVN

Verapamil, Diltiazem (IV)

16

What are the Class 4 drugs used to treat?

Four side effects of Class 4 drugs are dizziness, flushing, hypotension, and AV block. What is an additional side effect caused by Verapamil?

Class 4 Drugs

Tx: SVT

Side Effects
1) dizziness
2) flushing
3) hypotension
4) AV block
5) constipation -- Verapamil

17

Adenosine activates its receptors in what two locations? --> leading to decreased activity at these locations.

What are the two main therapeutic uses of Adenosine?

@ SAN, AVN

Therapy
1) AVN arrhythmia
2) SVT

18

What is the short-term therapy for Wolff-Parkinson-White syndrome?

Long-term therapy?

W-P-W Syndrome

Short-term tx: Adenosine

Long-term tx: Ablation