Antidysrhythmic and Inotropic Drugs

Question 1

Action potential outlined

Answer 1

Starts with Na+ influx (depolarization) via Na channels opening

Ends with K+ efflux (repolarization) via K+ channels opening

Question 2

PQRST Wave

Answer 2

P - atria
QRS - opening of Na channels (depolarization)
T - repolarization

Question 3

Supraventricular Tachycardia (2 kinds)

Answer 3

Atrial flutter - atria beating 220-430

Atrial fibrillation - most common SVT, messy electricity

Question 4

Ventricular Tachycardia

Answer 4

Most dangerous - zero cardiac output

Question 5

Antidysrhythmic Drugs 5 classifications

Answer 5

I - Na channel blockers
II - B-blockers
III - K channel blockers
IV - Ca channel blockers

Other - adenosine, digoxin

Question 6

Na channel blocker
Name one
Used for?

Answer 6

Lidocaine

Only used for ventricular dysrhythmias like PVCs, VT, and treating fibrillation after a MI

Question 7

B-adrenoreceptor antagonists
Name one
Mechanism

Answer 7

Metaprolol

Reduce sympathetic nervous system stimulation. They reduce calcium influx (Ca comes in through B-receptors).
AV block - reduce cell excitability

Question 8

K Channel blockers
Name one
Mechanism

Answer 8

Amiodarone

Prolong cardiac action potential, which extends the refractory period of cells so they aren’t ready to contract as early. Affects SA node
But it’s very dangerous!

Do not confuse with amlodipine (CCB)

Question 9

Ca channel blockers

Name two

Answer 9

Diltiazem, verapamil

Inhibits Ca entry, acts on AV node
AV block - only for atria, used for paroxysmal SVT
Exacerbates VT

Question 10

Adenosine

Answer 10

AV block - Slows conduction through AV node
Short half-life of 10-20 SECONDS
May cause asystole

Question 11

Inotropic Drugs
Name one
What do they do?

Answer 11

Digoxin (cardiac glycoside)

Increase the force of myocardial contraction

Question 12

Heart failure first line drugs (3)

Answer 12

Diuretics
B-blockers
RAAS drugs (ACE, ARBs)

Question 13

Inotropic, Chronotropic, Dromotropic

Meanings?

Answer 13

Force, rate, conduction of electrical impulses

Question 14

Digoxin
Mechanism:
What does it do?
Adverse effects:

Answer 14

Use it for heart failure!

Mechanism: Inhibits Na/K pump, so K doesn’t enter cell. Increases force of contraction (due to increased intracellular calcium)

What: Strengthens contractions, slows heart rate, slows electrical impulses
Increased stroke volume, decrease BP, promotes diuresis
Use it for supraventricular dysrhythmias

Adverse effects: digoxin toxicity - narrow therapeutic window, caused by low levels of K
COLORED VISION
can lead to bradycardia

Question 15

Digoxin toxicity treatment

Care

Answer 15

Digoxin immune F-antibody
Antidote is an antibody that binds to digoxin and reduces toxicity

Care: check APICAL pulse (not radial) for 1 full minute
Serum labs check potassium
pulse <90 in infant is red flag