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Pharmacology & Medical Chemistry II > Exam 1: Lecture 14/15, Anti-arrhythmic 1 & 2 > Flashcards

Exam 1: Lecture 14/15, Anti-arrhythmic 1 & 2 Flashcards

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1
Q

Class 1A drugs are…

A

fast Nav Channel blockers that prolong AP, little effect on phase 0 initiation

increase ERP

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2
Q

Examples of Class 1A drugs…

A

Quinidine and procainamide

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3
Q

Class 1B drugs are…

A

Nav channel blockers that shorten AP, limited effect on phase 0 initiation…state dependent block

decrease ERP

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4
Q

Examples of Class 1B drugs….

A

Lidocaine, mexiletine, ranolazine

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5
Q

Class 1C drugs are…

A

Nav channel blockers with no effect on AP length, act on initiation of phase 0….. state dependent block

No effect ERP

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6
Q

Examples of Class 1C drugs….

A

Flecainide, propafenone

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7
Q

Class 1A drugs work by…

A

reducing the rate and magnitude of depolarization, which decreases conduction velocity through non-nodal tissues

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8
Q

Class with intermediate association/dissociation Kinetics?

A

Class 1A

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9
Q

Class with Fast association/dissociation Kinetics?

A

Class 1B

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10
Q

Class with slow association/dissociation kinetics?

A

Class 1C

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11
Q

Procainamide

A

Class 1A, anti-arrhythmic but also local anesthetic

Voltage dependent blocker of Cardiac Ina and ikr (hERG)

Uses: Ventricular tacharrhythmias, supra ventricular tachycardia and A.fib

Can be given tablet, IM or IV

Side effects: Ventricular arrhythmia, LQT3, Bradycardia, hypotension, Drug-induced lupus

Narrow therapeutic window, any changes in weight/activity/etc can have effect

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12
Q

Lidocaine

A

Class 1B

Indicated for IV use in ventricular arrhythmia and carioversion (= getting normal heart beat)

Potential side effects: Hypotension, bradycardia, arrhythmias

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13
Q

Mexilatine (Mexitil)

A

Class 1B, anti-arrhythmic..oral analogue of lidocaine

uses: ventricular tachyarrhythmias (especially confirmed cases of LQT3), some types of chronic pain

state dependent blocker

Side effects: Ventricular arrhythmia, bradycardia and hypotension

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14
Q

Flecainide (Tambocor)

A

Class 1C anti-arrhythmic

** Suitable for children **

Uses: superventricualr tachycardia, Wolff-Parkinson White Syndrome, Brugada Syndrome

Side effects: Hypotension, bradycardia, arrhythmias

Avoid in pt with left ventricular hypertrophy, other form of HF, atherosclerosis….reduces ejection fraction + CO

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15
Q

Sotalol

A

Class 2 = beta blockers but also Class 3 = K+ channel blocker (increase AP duration)

B1/B2 antagonist,

Suitable for ventricular tachycardia and A.fib

Side effects: Dizziness, Headache, Shortness of breath, Bradycardia, Arrhythmia

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16
Q

Amiodarone

A

Class 3 = K+ channel blocker

** Blocks hERG and CaV channels ***

Uses: V-tachycardia, V-fib, A-fib, and supra ventricular tachycardia

Side effect: can cause anti-thyroid acton due to similar structure to thyroxine, Hypotension, Bradycardia, arrhythmias

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17
Q

Dronedarone

A

Multaq

non-ionidated version that lacks the thyroxine complication but has worse outcomes in patients with HF

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18
Q

Verapamil

A

Class 4 = Calcium channel blocker (reduce AP duration)

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19
Q

Adenosine

A

Class 5 = other

Commonly used IV for terminating Superventricualr tachycardia

can cause temporary cardiac systole

Acts at Adensoinde A1-receptors (Gai coupled…reduce cAMP/activate Girk) in the AV node leading to hyperpolarization

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20
Q

What is an arrhythmia?

A

change in velocity and/or route of AP conduction through the tissue

caused by disruption to the conduction system of the heart

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21
Q

congenital arrhythmias:

A

Mutations, polymorphisms or structural changes that you’re born with

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22
Q

Acquired arrhythmias:

A

primary or secondary disease process; can also be structural.

ie. left ventricular hypertrophy, adverse effects of a drug or signaling molecule in the conduction pathway.

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23
Q

Heart rate is controlled autonomously by….

A

Parasympathetic and sympathetic activity

intrinsic and integrated feedback from chemoreceptors

changes in either increase or decreasing heart rate

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24
Q

Cardiac conduction pathway

A

Starts at SA node “pacemaker cells”

Then goes to AV node, then Purkinje fibers conduct AP through and into ventricular muscle

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25
Q

Multiphase cardiac depolarization

A
  1. Depolarize atria
  2. Depolarize septum from left to right
  3. Depolarize anteroseptal region of myocardium toward the apex
  4. Depolarize bulk of ventricular myocardium, from endocardium to epicardium
  5. Depolarize posterior portion of base of the left ventricle
  6. The ventricles are now depolarized
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26
Q

Multiphase cardiac depolarization

A
  1. Depolarize atria
  2. Depolarize septum from left to right
  3. Depolarize anteroseptal region of myocardium toward the apex
  4. Depolarize bulk of ventricular myocardium, from endocardium to epicardium
  5. Depolarize posterior portion of base of the left ventricle
  6. The ventricles are now depolarized
27
Q

Negative chronotropes will…

A

decrease heart rate

28
Q

positive chronotropes will…

A

increase heart rate

29
Q

Negative Chronotrope drugs

A 
B blockers
M2 receptor agonist (acetylcholine)
Digoxin
Non-dihydropyridine CaV blockers (diltiazem and verapamil)
Adenosine (at A1-receptors)
30
Q

Positive chronotrope drugs

A 
Most B-receptor agonist
M2 receptor antagonists (atropine)
Milrinone
Theophylline
Caffeine (a1 antagonist)
31
Q

Dromotropic drug will…

A

affet AV node conduction

\+ = increase conduction
- = decrease conduction
32
Q

Phase 0

A

upstroke of the AP (Ica is slower than Ica+Ina)

33
Q

Phase 1

A

Rapid depolarization, inactivation of Ica/Ina and activation of outward K+ current (Ito)

34
Q

** Phase 2 **

A

plateau phase in ventricle.

duration depends on cintuned entry of Ca or Na, with NA/Ca exchanger NCX1

35
Q

Phase 3

A

depolarization due to multiple K+ channel currents

36
Q

Phase 4

A

Electrical diastole

Negative Vm,

In SA/AV nodal cells, If depolarized Vm leading to regenerative action potentials

37
Q

Most Prominent cardiac membrane protein channel

A

K+, hERG

38
Q

How does action potential pass from cell to cell?

A

via connexions

One cell will depolarize, and cause next cell to depolarize but slightly less, and so on and so on.

signal is fo about 6 cells, but must effect lost after 3

39
Q

Connexins and A.Fib

A

A.Fib can be associated with a change in number of connexions between cells

or

Change in connexion distribution, particularly lateralization

40
Q

Current definition of Bradycardia

A

HR <60 BPM

41
Q

Current definition of tachycardia

A

HR > 100 BPM

42
Q

Supraventricualr tachycardia

A

> 150 BPM, decreases CO….really dangerous

43
Q

Fibrillation

A

irregular heart rhythm in the atria or ventricles (A-Fib, V-Fib

44
Q

Atrial Fibrillation (A-Fib)

A

most common

random impulse cause atrial muscle to fibrillate

create local circuits, electricity travels in atria in chaotic fashion causing upper chambers to quiver

prevalence increase with age and following general anesthesia

45
Q

Atrial Flutter

A

Originate across larger areas of the atrium

heart contracts rapidly but with a regular rhythm

46
Q

Supraventricular tachycardias (SVT)

A

hard to control with med, usually requires ablation (using paddles to “reset” heart.

47
Q

Wolfe Parkinson White Syndrome

A

alternative pathway exists between the atria and ventricles known as “Bundle of Kent”

also known as Atrioventricular reciprocating tachycardia

48
Q

Tachycardia

A

rapid ventricular contractions may limit CO and reduce blood flow to the body

49
Q

Ventricular Fibrillation (V-Fib)

A

Most serious

random/chaotic impulse in ventricular walls

ventricle “quivers” instead of beats = no blood to aorta

requires immediate medical attention

50
Q

Bradycardia

A

slow HR

Can be due to slowing or failure of the SA node to initiate an impulse (too little SNS or too much PNS activity, physical damage to heart)

also can be due to blockage of signal from SA node (due to damage or dysfunctional AV node)

51
Q

Causes of arrhythmia

A

Structural changes to the myocardium

Dysregulation of intrinsic, integrated,autonomic responses

Ion channel issues

52
Q

Gene: SCN5A

A

Protein: Nav1.5a subunit
Channel: Nav1.5 (contains B subunit)
Current: Ina

53
Q

SCN5A mutation gain of function:

A

LQT3

54
Q

Gene:KCNQ1

A

Protein:Kv7.1 a subunit
Channel: IKs (contains KCNE1 subunit)
Current: iks

55
Q

KCNQ1 mutation loss of function:

A

LQT1

56
Q

Gene:KCNH2

A

Protein:Kv11.1a subunit
Channel:hERG
CurrentL Ikr

57
Q

KCNH2 mutation loss of function:

A

LQT2

58
Q

Long QT3 due to….

A

gain of Nav1.5 channel function

increasing the late current of Nav1.5 channels opposes depolarization of cardiomyocytes

59
Q

Drug-induced arrhythmia

A

Hydroxychloroquine found to increase

that’s why drugs are tested to see if they interact with hERG

mostly issue for aging population, not young adults

60
Q

Long QT2 due to…

A

loss of function or drug interactions with hERG channels

61
Q

Long QT syndrome….

A

reduced K+ current, slowing repolarization (phase 3)

62
Q

Short QT syndrome…

A

increased K+ current, repolarization (phase 3) is speed up

63
Q

Long QT1 due to…

A

mutations in the KCNQ1 subunit of the IKs K+ channel

Most common

64
Q

Jervell and Lange-nielsen syndrome

A

Long QT syndrome that manifests with sever, bilateral hearing loss

caused by specific mutations in Kv7.1

505 mortality by 15 yrs old if untreated

most serious form of LQTS

Pharmacology & Medical Chemistry II (43 decks)

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