Arrhythmias

Question 1

What are the 3 conditions for this to occur?

Answer 1

1. An obstacle must be present
2. there must be unidirectional block
3. Conduction time around the cicuit must be long enough that the retrograde impulse does not enter refractory tissue

Question 2

the 4 major pharmacologic mechanisms available to achieve the goals of antiarrhythmic agents

Answer 2

1. Na channel Blockade
2. blockade of SNS effects in the heart
3. prolongation of effective refractory period
4. Ca channel blockade

Question 3

Example of Condition where Reentry is anatomically determined

Answer 3

Wolff-Parkinson-White Syndrome

Question 4

Mechanisms of Arrhythmia

Answer 4

1. Disturbances in impulse formation
2. Disturbances in impulse conduction

Question 5

the time between phase 0 and sufficient and sufficient recovery of Na Channels in Phase 3

Answer 5

Refractory Period

Question 6

Describe the Action Potential Phases

Answer 6

1. Phase 0: Upstroke
2. Phase 1: Early-fast repolarization
3. Phase 2: Plateau
4. Phase 3: Repolarization
5. Phase 4: Diastole

Question 7

What are the common causes of Arrhythmia in clinical practice?

Answer 7

Digitalis (25%)

Anesthesia (50%)

Acute Myocardial Infarction (80%)

Question 8

frequency of SA node conduction

Answer 8

60-100 bpm

Question 9

lag time from SA node to AV node is?

this particularly provides what?

Answer 9

0.15s

provides time for atrial contraction to propel blood into ventricles

Question 10

What channels are open during the Phase 3 or Late Repolarization

Answer 10

Delayed Ca Rectifying Channels (slow and rapid)

Question 11

Differentiate the Phase 4 of pacemaker AP and non pacemaker AP

Answer 11

Pacemaker AP: (no true RMP) Slow inward Na current and Transient calcium current

Non Pacemaker AP: (RMP) K current

Question 12

Classification of antiarrhythmic agents and thier main actions

Answer 12

Class 1: Sodium Channel Blocker

Class 2: Sympatholytic (Beta Blocker)

Class 3: Prolongation of APD (Action Potential Duration) via blockade of rapid delayed rectifier potassium current

Class 4: Calcium current blocker

Question 13

Subgroups under class 1 of antiarrhythmic agents

Answer 13

Class 1A: prolong APD;dissociate from channel with intermediate kinetics

Class 1B: shorten APD; dissociate from the channel with rapid kinetics

Class 1C: minimal effects on the APD; dissociate for the channel with slow kinetics

Question 14

what type of drug action is described by “the channels that are being used frequently/in an active state are mosre susceptible to block

Answer 14

use dependent / state dependent

Question 15

mechanisms by which antiarrhythmic agents slow conduction

Answer 15

1. steady-state reduction in the number of available unblocked channels
2. prolongation of recovery time of channels (increasing effective refractory period)

Question 16

Drugs that prolong APD (group 1A) (3)

Answer 16

Procainamide

Quinidine

Disopyramide

Question 17

anti arrhythmic drug that has an SLE-like Side Effects

Answer 17

Procainamide

Question 18

Side effects include tinnitus /cinchonism

Answer 18

Quinidine

Question 19

True/False. Disopyramide is an antiarrhythmic agent indicated for Heart Failure Px

Answer 19

False. it is CI for Heart Failure Px

Question 20

blocks activated and inactivated sodium channels with rapid kinetics; has a selective conduction in depolarized cells

Answer 20

Lidocaine

Question 21

what acute phase protein binds lidocaine making less free drug available to exert is pharmacologic effect

Answer 21

Alpha-1-Acid Glycoprotein

Question 22

the agent of choice for termination of ventricular tachycardia and prevention of ventricular fibrillation after cardioversion in the setting of acute ischemia

Answer 22

Lidocaine

Question 23

an orally active congener of Lidocaine

Answer 23

Mexilitine

Question 24

potent inhibitor of sodium and potassium channels with slow unblocking kinetics (does not prolong the AP or QT interval)

Answer 24

Flecainide

Question 25

very effective in suppressing premature ventricular contractions

Answer 25

Flecainaide

Question 26

A Class 1C antiarrhythmic agent that has similarities with propranolol

Answer 26

Propafenone

Question 27

an anti arrhythmic phenothiazine derivative; for ventricular arrhythmias

Answer 27

Moricizine

Question 28

Class 2 Anti-arrhythmic agents

Answer 28

Propanolol
Esmolol
Sotalol*

Question 29

Action potenial prolongation is least marked at fast rates(where it is desirable) and most marked at slow rates (where it can contribute to the risk of torsades de pointes)

Answer 29

“Reverse-use dependence”

Question 30

Class 3 Anti Arrhythmic drugs (7)

Answer 30

Amiodarone
Dronedarone
Celivarone
Vernakalant
Sotalol
Dofetilide
Ibutelide

Question 31

What are the cardiac effects of Amiodarone

Answer 31

1. Blockade of Ik_r
2. Blockade of Iks (at chronic admin)
3. slows HR and AV node conduction

Question 32

A structural analogue of Amiodarone without its toxic effects of the thyroxine metabolism

Answer 32

Dronedarone

Question 33

At low doses, what action of sotalol is predominant?

Answer 33

Beta blocking action

(high dose: prolonged AP)

Question 34

Action potential prolongation mechanisms of

Ibutilide

Dofetilide

Answer 34

Ibutelide: (-) rapid delayed rectifier potassium current and (+) slow inward soudium current

Dofetilide: dose dependent (-) rapid delayed rectifier potassium current

Question 35

the prototype of Class 4 AntiArrhythmic agents

Answer 35

Verapamil

Question 36

Calcium channel blockers that do not have antiarrhythmic effects

Answer 36

Dihydropyridines (e.g. Nifedipine)

Question 37

Verapamil suppresses Early or Delayed After Depolarization?

Answer 37

Both

Question 38

Miscellaneous Antiarrhythmic agents (3)

Answer 38

Adenosine
Magnesium
Potassium

Question 39

which drug is renderred less effective by theophylline and caffeine but potentiated by dipyridamole

Answer 39

Adenosine

(Theophylline and Caffeine: Adenosine receptor blockers
Dipyridamole: adenosine uptake inhibitors)