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ESA 2- Cardiovascular System > Drugs Acting on the CVS > Flashcards

Flashcards in Drugs Acting on the CVS Deck (52)
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1

What are cardiovascular drugs used to treat?

Arrythmias
Heart failure
Angina
Hypertension
Risk of thrombus formation

2

What can cardiovascular drugs alter?

The rate and rhythm of the heart
The force of myocardial contraction
Peripheral resistance and blood flow
Blood volume

3

What can cause arrhythmias?

Ectopic pacemaker activity
After-depolarisations
Re-entry loop

4

How can ectopic pacemaker activity lead to arrhythmias?

Damaged area of myocardium becomes depolarised and spontaneously active. The latent pacemaker region is activated due to ischaemia, and dominates over the SA node

5

What are after-depolarisations?

Abnormal depolarisations following the action potential

6

What are after-depolarisations thought to be caused by?

High intracellular Ca

7

What does a longer action potential in after-depolarisation lead to?

A longer QT interval

8

What causes a re-entry loop?

Conduction delay, whereby normal spread of excitation is disrupted due to damaged area .

9

When will a re-entry loop occur?

When there is incomplete conduction damage leading to uni-directional block

10

What happens if you get several small re-entry loops in the atria?

Atrial fibrillation

11

What can cause several small reentry loop in the atria?

Being stretched over time

12

What are the basic classes of anti-arrythmic drugs?

I. Drugs that block voltage gated Na channels
II. Antagonists of ß-adrenoreceptors
III. Drugs that block K channels
IV. Drugs that block Ca channels

13

What is a typical example of a class I anti-arrythmic drug?

Lidocaine

14

What channels does lidocaine block?

Voltage gated Na channels
Only those that are in an open or inactive state

15

How quickly does lidocaine dissociate?

Quickly- in time for next AP

16

What is the advantage of lidocaine?

Normal firing of APs is not stopped, but it prevents the firing of APs too close to one anoterh

17

Why can lidocaine be used as an anti-arrythmic?

Because Na channels are blocked, after-depolarisations cannot trigger another AP

18

Give two examples of class II anti-arrythmic drugs

Propanolol
Atenolol

19

How do class II anti-arrythmic drugs work?

They block sympathetic action by acting on ß1 receptors in the heart, decreasing the slope of the pacemaker potential in the SAN
Inhibits adenylyl cyclase, decreasing intropy

20

What are class II anti-arrythmic drugs also known as?

Beta-blockers

21

When are beta-blockers used?

After a MI

22

What are beta-blockers used after an MI?

To combat increases in sympathetic activity
To reduce oxygen demand of myocardium

23

How do class III anti-arrythmic drugs work?

Prolong the action potential, by blocking K channels (which are responsible for repolarisation). The absolute refractory period is lengthened, preventing another AP from occurring too soon

24

Why are class III drugs not generally used?

Because they can also be pro-arrythmic

25

Give an example of a class IV anti-arrythmic drug?

Verapamil

26

How do class IV drugs work?

Decreases slope of pacemaker potential at SA node
Decreases AV node condutction
Decreases force of contraction
Some coronary and peripheral vasodilation

27

Where is adenosine produced?

Endogenously

28

What does adenosine act on?

A1 receptors at AV node

29

What kind of receptor are A1 receptors?

GPCR

30

What happens on stimulation of A1 receptors?

Inhibits adenylyl cyclase