AntiArrythmics Intro - Nordgren

Question 1

Name the three factors that if deviated will lead to a cardiac arrhythmia:

Answer 1

Rate of Impulse
Site of impulse origin
Conduction of the impulse

Question 2

Describe the status of the gates of a sodium channel when it is “resting”, “activated”, and “inactivated.”

Answer 2

Resting: Activation gate is closed - Inactivation gate is open
Activated: Both activation/inactivation gates are open
Inactivated: Activation gate is open - inactivation gate closed

Question 3

Atrial, purkinje, and ventricular cells differ from SA and AV nodal cells in the channel that is responsible for their depolarization. What ion channel is responsible for each?

Answer 3

Atrial, purkinje, and ventricular = Na Current

SA and AV = Ca Current

(Remember that the Ca channels are inactivated and activated in much the same way as Na channels BUT the transitions occur more slowly and at more positive potentials)

Question 4

In all heart cell types, what is responsible for the occurrence of phase 3 of the action potential?

Answer 4

Phase 3 is final repolarization.

This results fromt he completion of Na/Ca inactivation and the growth of K permeability.

Question 5

The time period between Phase 0 and the point in Phase 3 where Na channels have recovered to allow another Action Potential is known as:

Answer 5

The refractory period!

Question 6

What happens to the number of available Na channels under optimal and suboptimal resting membrane potential conditions when a Na-blocking drug is given?

Answer 6

Optimal Conditions (very negative potential) = Number of available channels is decreased

Suboptimal Conditions (less negative potential) = Number of channels will increase at a sharper slope because of drug blockade and inactivation gate closures

Question 7

How will depolarization of membrane potential affect the recovery time of Na channels?

Answer 7

Depolarized cells recovery more SLOWLY.

Refractory period will increase
Na channel blockade is going to prolong the recovery time a ton more also

Question 8

What happens to Na currents when the cell’s resting membrane potential is depolarized to -55mV?

Answer 8

Na currents are abolished (inactivated)

SA and AV nodal cells don’t have the same effect because their normal resting membrane potential is -50 to -70. Much more depolarized than normal cardiac cells.

Question 9

Disturbances of impulse formation and impulse conduction leads to:

Answer 9

Arrhythmias

Question 10

Afterdepolarizaton are one of the disturbances of impulse formation. What are the differences between early and delayed afterdepolarizations?

Answer 10

Early:
Occur during the AP
Exacerbated at SLOW heart rates
Another spike during the normal plateau phase

Delayed:
Occur just after AP
Exacerbated at fast heart rates
Spike from resting potential

Question 11

A heart block occurs when the electrical signal is slowed or disrupted as it moves through the heart.
What’s the difference between a partial and complete block?

Answer 11

Partial: Electrical signals are delayed and/or occasionally blocked

Complete: Electrical signals completely blocked

Question 12

What is reentry?

Answer 12

Impulses reenter and excite areas of the heart more than once.

Question 13

Explain Wolf-Parkison-White Syndrome:

Answer 13

In this REENTRY syndrome, an abnormal anatomical connection between the atria and ventricle called the Bundle of Kent is present.
This bundle allowed for an impulse to be conducted from the ventricles back into the atria (reentry) or cause the ventricles to contract prematurely.

Question 14

What kinds of anti-arrhythmic drugs use a mechanism of prolonging the effective refractory period?

Answer 14

Class 3 drugs - The K channel blockers

Question 15

What is the method of action of Class 1 drugs?

Answer 15

Na Channel blockers

They alter the action potential duration and change the Na channel kinetics

Question 16

How do class 2 drugs work?

Answer 16

Beta-adrenoceptor blockade

-Block SNS effects in the heart

Question 17

How do class 4 drugs work?

Answer 17

Ca Channel blockers

-Slow conduction where depolarization is Ca dependent

Question 18

What is the advantage of “use” or “state-dependent” drugs?

Answer 18

Ideally you want to bind well to activated/inactivated channels and poorly to rested channels.

These drugs will then block activity in fast tachycardia and loss of resting potential when there are many inactivated channels during rest

Question 19

What do you have to be careful with as you increase the dose of Na channel blockers?

Answer 19

At higher doses, the lack of specificity increases - can also block K channels.

Question 20

What kind of arrhythmia do you have if you are getting early extra beats originating int he atria?

Answer 20

Premature atrial contractions

Subtype of Supraventricular

Question 21

Rapid, unusual regular rhythm originating above the ventricles.
Name that arrythmia:

Answer 21

Paroxysmal Supraventricular Tachycardia

Question 22

Name that arrythmia:
Extra abnormal pathway between ventricles and atria.
(you get a slurred upstroke to QRS)

Answer 22

Accessory pathway tachycardia

Question 23

Rapid heart rate due to more than one path through the AV node:
Name that arrythmia:

Answer 23

AV nodal reentrant tachycardia.
-Could be:
Atrial tachycardia
Atrial fibrillation (disorganized, rapid, irregular)
Atrial flutter (organized and regular

Question 24

Early extra beats beginning in the atria:

Name that arrythmia:

Answer 24

Premature ventricular contractions

Question 25

Rapid ventricular rhythym:

Answer 25

Ventricular tachycardia

Question 26

What do you gotta do if someone has ventricular fibrillation?

Answer 26

CPR and defibrillation, FAST!

Question 27

IF the time it takes the heart to contract and then recover is prolonged…
Name that arrythmia:

Answer 27

Long QT syndrome

kind of ventricular arrhythmia

Question 28

Arrhythmia can be broadly categorized as ventricular, supraventricular, or ?

Answer 28

Bradycardia!