Arrhythmia 2 - better flash cards

Question 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)?

Answer 1

Class 1A

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

APD, ERP: both increased

Question 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?

Answer 2

Class 1A

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

2) Procainamide
- -hypotension, lupus

3) Disopyramide

Tx: atrial & ventricular arrhythmias

Question 3

Class 1B

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

Answer 3

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

Question 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?

Answer 4

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

Question 5

What are two important side effects of Lidocaine?

Answer 5

seizures/neuro; CV depression

Question 6

Class 1C

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

Answer 6

Class 1C

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

Question 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.

Answer 7

Flecainide
–refractory VT, refractory SVT

Propafenone
–has active metabolites

Question 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?

Answer 8

Most potent Na chnl blockers

Contraindication: structurally abnormal hearts

Question 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?

Answer 9

Class 2 Drugs: Beta Blockers

Mechanism: beta receptor blockade…

• -> decrease cAMP
• -> reduced Na, Ca currents
• -> suppress abnormal pacemakers in AV node

Question 10

Class 2 Drugs: Beta Blockers

List the three beta blockers used.

What are its two main arrhythmia-related therapeutic uses?

Answer 10

1) Metoprolol
2) Atenolol
3) Nadolol

Therapy:

1) post-MI prophylaxis
2) SVT

Question 11

Class 3 Drugs

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

Answer 11

Class 3 Drugs

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

Question 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?

Answer 12

Amiodarone

• -very efficacious
• -iodine related toxicity

Dronedarone
–less efficacious, less toxic version of Amiodarone

Question 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?

Answer 13

Sotalol

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

Question 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?

Answer 14

Dofetilide

• -atrial selective
• -Torsades

Ibutilide

Question 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?

Answer 15

Class 4 Drugs

Mechanism

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

Verapamil, Diltiazem (IV)

Question 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?

Answer 16

Class 4 Drugs

Tx: SVT

Side Effects

1) dizziness
2) flushing
3) hypotension
4) AV block
5) constipation – Verapamil

Question 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?

Answer 17

@ SAN, AVN

Therapy

1) AVN arrhythmia
2) SVT

Question 18

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

Long-term therapy?

Answer 18

W-P-W Syndrome

Short-term tx: Adenosine

Long-term tx: Ablation