Chapter 24: Cardiac Contractility

Question 1

What are the 3 major effects of Digoxin?

Answer 1

1. inhibit Na/K ATPase; increased cytoplasmic Ca; –> POSITIVE INOTROPY
2. Inhibit sympathetic outflow; increase vagal ton –> Decrease HR
3. Decrease AV node conduction velocity; prolong refractory period

Question 2

Digoxin can be used to treat _______?

Answer 2

Systolic heart failure
Supraventricular arrhythmias (a fibb, a flutter, paroxysmal a tach)

Question 3

What does slowing the AV node conduction velocity accomplish?

Answer 3

Decreases ventricular rate and allows for improved filling

Question 4

Major side effects of digoxin?

Answer 4

Arrhythmias, premature ventricular contraction, muscle weakness, fatigue, blurred vision, yellow-green halo around visual images, nausea and vomiting, hyperkalemia

(nausea and vomiting due to increased vagal tone)

Question 5

Digoxin + ______ = potential for high grade AV block

Answer 5

B blockers (both act to block AV node conduction)

Question 6

Name things that can predispose to digoxin toxicity

Answer 6

Renal failure - digoxin is urinary excretion ONLY
K wasting diuretics and hypokalemia
Verapamil
Quinidine 
Amiodarone

Question 7

How do you treat digoxin toxicity?

Answer 7

Normalize K levels

Digoxin immune fab (keep resuscitation equipment available)

Question 8

Does digoxin improve survival?

Answer 8

No…symptomatic tx only

Question 9

Where do Beta Agonists work? How?

Answer 9

B1 receptors - G protein coupled receptor - increase cAMP

Question 10

What kinds of actions do B agonists have?

Answer 10

Inotropic, chronotropic, and lusitropic

Question 11

How does dopamine act at low doses?

Answer 11

D1 receptors

Peripheral vasodilation

Question 12

How does dopamine act at intermediate doses?

Answer 12

B1 and B2 receptors

Vasodilation (B2)
Increased contractility and HR (B1)

Question 13

How does dopamine act at high doses?

Answer 13

alpha-1 receptors

generalized vasoconstriction

Question 14

Coadministration of _____ with dopamine (B agonist) can decrease dopamine metabolism. This can lead to _______ and ______.

Answer 14

MAOI

tachycardia
arrhythmia

Question 15

Dopamine clinical application? (IV administration btw)

Answer 15

shock

adjunct to increase cardiac output, blood pressure, and urine flow

Question 16

Dobutamine MOA?

Answer 16

B agonist

Racemix mix - predominantly B1 with modest B2

Question 17

Inotropic drug of choice for acute cardiogenic circulatory failure?

Answer 17

dobutamine

Question 18

Epinephrine MOA?

Answer 18

Non selective B1, B2, alpha 1, alpha 2 agonist

Question 19

Clinical applications of epinephrine?

Answer 19

Bronchospasm
Anaphylactic shock
Glaucoma (open angle)
Cardiac resuscitation 
Prolong local anesthetics

Question 20

Major adverse effects of epinephrine?

Answer 20

Arrhythmias
Cerebral hemorrhage
Headache, nervousness, tremor, HTN, palpitations, tachycardia (from increased sympathetics)

Question 21

Clinical application of norepinephrine ?

Answer 21

blood pressure support in acute hypotensive states (shock)

compare to epinephrine, which is only used in ANAPHYLACTIC shock

Question 22

Norepi MOA?

Answer 22

B1, alpha 1, alpha 2 agonist

Question 23

Do not use norepinephrine with what drugs?

Answer 23

MAOIs
Imipramine
amitryptiline

Question 24

Do not use norepinephrine in patients with hypotensions DUE TO ______

Answer 24

loss of blood volume

Question 25

Isoproterenol may be useful in treating patients with ________ and _______

Answer 25

refractory bradycardia that didnt respond to atropine B blocker overdose

Question 26

Isoproterenol is a _______ (drug class)

Answer 26

B agonist - nonselective at B1 and B2

Question 27

Isoproterenol is given IV for arrhythmias, bradycardia, heart block, and shock. For what problem is it given via inhalation?

Answer 27

bronchospasm

Question 28

Name the phosphodiesterase inhibitors

Answer 28

Theophylline Inamrinone Milrinone Vesnarinone

Question 29

How do phosphodiesterase inhibitors work? What are the effects?

Answer 29

Inhibit PDE enzymes --> increase cAMP = inotropic and lusitropic effects = relax vascular smooth mm = thereby decrease pre-load (vasodilation) AND after-load (arteriodilation)

Question 30

Major adverse effect of inamrinone (not as much in milrinone)

Answer 30

thrombocytopenia

Question 31

PDE inhibitors can be used only in what type of cases?

Answer 31

SHORT TERM tx of severely failing circulation....when conventional therapy has failed

Question 32

Long term use of PDE inhibitors is linked to _______?

Answer 32

increased mortality

Question 33

Inamrinone, milrinone, and vesnarinone increase ______ and _________?

Answer 33

Increase contractility | Increase rate/extent of diastolic relaxation