K+ and Ca2+ Antiarrhythmics Flashcards Preview

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Flashcards in K+ and Ca2+ Antiarrhythmics Deck (21):
1

Primary role of K+ in myocyte action potential?

repolarization (phase 3)

2

Common EKG effect of all class III drugs with prolonged repolarization?

prolonged QT

3

Class III antiarrhythmic

prolongs AP

also potent Na+ channel blocker

weak Beta and Ca2+ blocker

slows HR and AV node conduction

Amiodarone

4

Extracardiac effects of Amiodarone

peripheral vasodilation

5

Toxicity of Amiodarone

Bradycardia and heart block in pts w/ preexisting SA or AV node disease

Drug accumulation in tissue (LONG half life)

Blocks peripheral conversion of thyroxine (T4) to triiodothyronine (T3)--source of inorganic iodine

6

PK if Amiodarone:

Hepatic metabolism

Major metabolite is bioactive --- long last effects
-pulm toxicity
-abnormal liver function
-skin deposits
-corneal microdeposits (halos, optic neuritis, blindness)
-hypo/hyper thyroidism

CYP3A4 drug interactions

inhibits several P450s --> icr. levels of other drugs (ie. warfarin, statins, digoxin)

7

Uses of Amiodarone:

V tach
V fib
A fib
A flutter

8

Most important adverse effect of Amiodarone:

dose related Pulmonary Toxicity

9

Class III

Very selective K+ blocker

Maintenance and restoration of NSR in a fib

Dofetilide

10

Dofetilide

Class?

Toxicity?

PK?

Use?

Class III (very selective K+ blockade)

Tox: life threatening ventricular arrhythmias

PK: 100% bioavailability, hepatic met. CYP3A4

Use: a fib

contraindications: long QT, bradycardia, hypokalemia

11

Class III

also slow inward Na+ ACTIVATOR --> delays repolarization (inhibits Na+ inactivation, increasing ERP)

Toxicity: long QT, torsades --> life threatening ventricular arrhythmias

PK: hepatic

Use: acute conversion of a fib/flutter in NSR

Ibutilide

12

Target channel for Class IV drugs?

L-type Ca2+

-VSM relaxation

-decreased cardiac contractility (less Ca2+ available to bind troponin)

13

Class IV drugs effect on nodal cells?

-decreased HR

-decreased conduction (especially AV node)

14

Therapeutic indications for Class IV?

HTN (arteriole SM relaxation)

Angina (decreased afterload--decreased O2 demand)

Arrhythmias (decreased depol rate, decreased conduction velocity)

15

What are the two subclasses of Class IV drugs?

How do they differ?

1. Dihydropyridines -- smooth muscle selective --> can cause reflex cardiac stimulation

2. Non-dihydropyridines -- more selective for myocardium

**Diltiazem does both -- able to reduce arterial pressure without same degree of reflex cardiac stimulation

16

Class IV drugs should not be used in conjunction with?

Beta blockers

17

Non-DHP Class IV

more specific for myocardium

used in SVT, a fib/flutter

Contraindicated in WPW

Verapamil

18

Non-DHP Class IV

More equivalent selectivity for vascular and myocardial SM

Diltiazem

19

Activates K+

inhibits Ca2+ L type

results in hyperpolarization and suppression of nodal tissue

used for SVT

not effective for a fib/flutter

Adenosine

***contraindicated in 2 and 3 deg AV block

20

Inhibits Na+/K+/ATPase pump

improves contractility (reverses NCX--> more Ca2+ in cell)

Decreases HR

activates vagal efferents to heart

primarily used in HF (also a fib/flutter)

Digoxin

21

Digoxin toxicity on EKG looks like?

Salvadore Dalis mustache

increased PR

flattened T-wave

Decreased QT