Lecture 12, 13

Question 1

Where are impulses initiated?

Answer 1

SA Node

Question 2

What follows SA Node depolarization?

Answer 2

Atrial Activation

Question 3

After Atrial Activation, where do impulses go through?

Answer 3

AV Node

Question 4

What kind of conduction is AV?

Answer 4

Slow

Question 5

After AV node, what is activated?

Answer 5

His Purkinje System

Question 6

After His Purkinje, where does the impulse spread?

Answer 6

Ventricular myocardium

Question 7

Antiarrythmia drugs work by modulating the ____ & ____ to change how the heart works

Answer 7

ligand, voltage channels

Question 8

What is the order of phases of the fast cardiac action potential?

Answer 8

4, 0, 1, 2, 3, 4

Question 9

Action potential starts in diastole, MP is at -90

Answer 9

Phase 4 (1st one)

Question 10

Normally, the Na+ channels are closed, in depolarization they rapidly open & Na floods in, cell goes from -90 to +55 in less than a second

Answer 10

Phase 0

Question 11

Na channels close, Voltage Ca2+ (L-type) channels open, Ca2+ keeps cell at positive potential, cell stays depolarized for longer time

Answer 11

Phase 1

Question 12

Open K+ channels, K+ leaves, makes cell become negative again

Answer 12

Phase 2

Question 13

Repolarization, voltage gated K+ channel opens

Answer 13

Phase 3

Question 14

Cell is still repolarizing, Na+ inside cell, K+ outside, Na+/K+ ATPase pump fixes it

Answer 14

Phase 4 (last one)

Question 15

Effect of Local Anesthetics on the Fast Cardiac AP:

Answer 15

1. Block Na+ channels, so slope of phase 0 less steep= longer to get to +55
2. Longer refractory period due to slower recovery from inactivation
3. Increased threshold – Stabilize the membrane

Question 16

Effect of drugs that block K+ Channels:

Answer 16

1. AP takes longer to repolarize
2. Increase APD
3. Decrease HR by increasing refractory period by blocking K+ channels

Question 17

P wave

Answer 17

Atrial Depolarization

Question 18

QRS complex

Answer 18

Ventricular Depolarization

speed of conduction

Question 19

T wave

Answer 19

Ventricular Repolarization

Question 20

PR interval

Answer 20

Atrial & AV conduction time

Question 21

QT interval

Answer 21

Action Potential duration

Question 22

What happens to ECG if a drug slows AV conduction by DECREASING slope of phase 0?

Answer 22

Increase PR

Question 23

What happens to ECG if a drug slows conduction of a ventricle by decreasing slope of phase 0? What drug does this?

Answer 23

Increase QRS width

Local Anesthetics

Question 24

What happens to ECG if a drug blocks K+ channels?

Answer 24

Lengthen QT

Increase AP duration of the ventricle

Question 25

Class 1A Action: Drugs:

Answer 25

Act: Moderate phase 0 Drugs: Quinidine, Procainamide

Question 26

Class 1B Action: Drugs:

Answer 26

Act: No change phase 0 Drugs: Lidocaine

Question 27

Class 1C Action: Drugs:

Answer 27

Act: Marked phase 0 Drugs: Flecainide

Question 28

Class 2 Action: Drugs:

Answer 28

Act: Beta Adrenergic blockers Drugs: Propranolol, Esmolol

Question 29

Class 3 Action: Drugs:

Answer 29

Act: Prolong repolarization Drugs: Amiodarone, Sotolol, Dofetalide, Ibuillide

Question 30

Class 4 Action: Drugs:

Answer 30

Act: Ca+ channel blockers Drug: Verapamil, Diltiazem

Question 31

``` 1A Quinidine MOA: Act: ECG: Effects: Use: Caution ```

Answer 31

MOA: block Na+ & some K+ channels Act: slows CV in ventricle, APD increases ECG: Widened QRS & QT Effects: Vagolytic action, makes supra ventricular tachycardias worse Use: Wide, atrial flutter, fibrillation, ventricular tachycardias Caution: Proarrhythmic, increase in QT cause Torsades

Question 32

``` 1A Procainamide MOA: Act: ECG: Use: Caution: ```

Answer 32

MOA: block Na+ & some K+ channels Act: slows CV in ventricle & atria, APD increases ECG: widened QRS & QT Use: wide, atrial flutter, fibrillation, ventricular tachycardias Caution: Proarrhythmic, not used long term, lupus

Question 33

1B Lidocaine MOA: Use:

Answer 33

MOA: Pure Na+ channel blocker Use: ER, only works when heart speeds up, ventricular tachyarrhythmias

Question 34

Oral version of Lidocaine?

Answer 34

Mexiletine

Question 35

``` 1C Flecainide MOA: Action: Use: Caution: ```

Answer 35

MOA: Blocks Na+ & K+ channels -- better in atria K channels Action: Long binding constant -> stays on channel long -> marked phase 0, tonic & rate dependent block Use: Atrial flutter & fibrillation Caution: Proarrhythmic

Question 36

``` Propanolol, Atenolol, Timolol MOA: Action: Use: Caution: ```

Answer 36

MOA: B1/B2 blocker Action: Slow AV conduction, HR decreased Use: Sympathetic sinus tachycardias, re-entry rhythms in & around AV Caution: with other drugs that lengthen AV conduction time -- Ca+ blocker, digitalis, asthma, diabetic

Question 37

Esmolol | Use:

Answer 37

Use: supraventricular arrhythmias | very short 1/2 life

Question 38

Amiodarone MOA: Use: Toxicity:

Answer 38

MOA: Block Na, K, Ca channels, B receptors -- long 1/2 life Use: wide, supra ventricular arrhythmias, post MI, HF Tox: cholesterol in eye, blue skin, pulmonary, hepatic, thyroid

Question 39

Sotalol MOA: Use:

Answer 39

MOA: K channel and B blocker Use: atrial flutter & fibrillations & ventricular tachycardias

Question 40

What is the only antiarrythmic used in heart failure?

Answer 40

Amiodarone

Question 41

``` Dronedarone Cardiac Effects: Uses: SE: Contraindicated: ```

Answer 41

CE: same as Amiodarone, lacks an Iodine & less fat soluble Use: prevent recurrence of atrial fibrillation/ flutter -- not good at converting atrial fib/ flutter SE: Bradycardia, long QT, Torsades, metabolized by antifungals Contrain: HF

Question 42

``` Dofetilide MOA: Action: Use: Caution: ```

Answer 42

MOA: Selective K+ channel blocker Act: prolong AP duration Use: atrial fib, MI, HF Caution: Torsades

Question 43

Ibutilide MOA: Use: Caution:

Answer 43

MOA: similar to dofetilide Use: convert atrial fib or flutters to normal rhythm Caution: Torsades

Question 44

Verapamil, Diltiazem Action: Caution:

Answer 44

Act: Like B blocker - dec. slope of phase 0 (Ca++), slow conduction through AV node - inc. refractory period in AV node - break re-entry rhythms around AV node. - dec. slope of phase 4 in SA node to slow HR Caution: drugs that slow AV conduction, HYPOtension

Question 45

Adenosine | Use:

Answer 45

Very short 1/2 life, slows HR Slow AV conduction Acute Termination of re-entrant supra ventricular arrhythmias esp around AV

Question 46

Atropine | Use:

Answer 46

Inc HR | Tx Vagal Bradycardia

Question 47

Mg | Tx:

Answer 47

Tx: Torsades

Question 48

Digitalis Action: Tx:

Answer 48

Act: Slow AV conduction Tx: atrial flutter, atrial fib esp during HF

Question 49

What is the treatment of choice for unstable, life-threatening cardiac arrhythmias?

Answer 49

DC Cardioversion