Drugs Acting on the CVS

Question 1

What are cardiovascular drugs used to treat?

Answer 1

Arrythmias
Heart failure 
Angina 
Hypertension 
Risk of thrombus formation

Question 2

What can cardiovascular drugs alter?

Answer 2

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

Question 3

What can cause arrhythmias?

Answer 3

Ectopic pacemaker activity
After-depolarisations
Re-entry loop

Question 4

How can ectopic pacemaker activity lead to arrhythmias?

Answer 4

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

Question 5

What are after-depolarisations?

Answer 5

Abnormal depolarisations following the action potential

Question 6

What are after-depolarisations thought to be caused by?

Answer 6

High intracellular Ca

Question 7

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

Answer 7

A longer QT interval

Question 8

What causes a re-entry loop?

Answer 8

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

Question 9

When will a re-entry loop occur?

Answer 9

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

Question 10

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

Answer 10

Atrial fibrillation

Question 11

What can cause several small reentry loop in the atria?

Answer 11

Being stretched over time

Question 12

What are the basic classes of anti-arrythmic drugs?

Answer 12

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

Question 13

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

Answer 13

Lidocaine

Question 14

What channels does lidocaine block?

Answer 14

Voltage gated Na channels

Only those that are in an open or inactive state

Question 15

How quickly does lidocaine dissociate?

Answer 15

Quickly- in time for next AP

Question 16

What is the advantage of lidocaine?

Answer 16

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

Question 17

Why can lidocaine be used as an anti-arrythmic?

Answer 17

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

Question 18

Give two examples of class II anti-arrythmic drugs

Answer 18

Propanolol

Atenolol

Question 19

How do class II anti-arrythmic drugs work?

Answer 19

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

Question 20

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

Answer 20

Beta-blockers

Question 21

When are beta-blockers used?

Answer 21

After a MI

Question 22

What are beta-blockers used after an MI?

Answer 22

To combat increases in sympathetic activity

To reduce oxygen demand of myocardium

Question 23

How do class III anti-arrythmic drugs work?

Answer 23

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

Question 24

Why are class III drugs not generally used?

Answer 24

Because they can also be pro-arrythmic

Question 25

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

Answer 25

Verapamil

Question 26

How do class IV drugs work?

Answer 26

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

Question 27

Where is adenosine produced?

Answer 27

Endogenously

Question 28

What does adenosine act on?

Answer 28

A1 receptors at AV node

Question 29

What kind of receptor are A1 receptors?

Answer 29

GPCR

Question 30

What happens on stimulation of A1 receptors?

Answer 30

Inhibits adenylyl cyclase

Question 31

How does adenosine work as an anti-arrythmic?

Answer 31

It enhances K conductance and hyperpolarises cells of conduction tissue

Question 32

Essentially, what does adenosine do?

Answer 32

'Resets' the heart

Question 33

What drugs have an important role in in the treatment of chronic heart failure?

Answer 33

ACE-inhibitors | Diuretics

Question 34

How to ACE-inhibitors treat chronic heart failure?

Answer 34

They prevent the formation of the vasoconstrictor angiotesin II, thus promoting vasodilation of arterioles and venus dilation. This decreases both afterload and preload on the heart

Question 35

Why do ACE-inhibitors have a diuretic action?

Answer 35

Because angiotensin II promote aldosterone release from the adrenal cortex (zona glomerulosa)

Question 36

Why does the inhibition of aldosterone act as a diueretic?

Answer 36

Aldosterone causes Na and water retention, increasing blood volume- so reducing it decreases blood volume and decreases pre-load to the heart

Question 37

What is the principle of angina treatment?

Answer 37

Reducing the work load of the heart

Question 38

What drugs are used to treat angina?

Answer 38

ß-blockers | Organic nitrates

Question 39

What drugs improve blood supply to the heart?

Answer 39

Organic nitrates | Ca channel blockers

Question 40

How do organic nitrates treat angina?

Answer 40

The reaction of organic nitrates with thiols (-SH groups) in vascular smooth muscle causes NO2- to be released. NO2- is reduced to NO, which is a powerful vasodilator. NO activates guanylate cyclase, increasing cGMP and lowering intracellular Ca2+ to cause relaxation of vascular smooth muscle.

Question 41

What is the primary action or organic nitrates?

Answer 41

Acts on the venous system as a venodilator, lowering central venous pressure and preload. The heart fills less; therefore force of contraction is reduced (Starlings Law).

Question 42

What is the secondary action of organic nitrates?

Answer 42

Acts on the coronary arteries, improving O2 delivery to the ischaemic myocardium.

Question 43

What do some heart conditions carry?

Answer 43

An increased risk of thrombus formation

Question 44

Give 2 examples of heart conditions that carry an increased risk of thrombus formation

Answer 44

Atrial fibrillation | Valve disease

Question 45

What may be used when a heart condition carries an increased risk of thrombus formation?

Answer 45

Anti-thrombotic drugs

Question 46

Give an example of an anti-thrombotic drug?

Answer 46

Warfarin

Question 47

Give an example of an anti-platelet drug?

Answer 47

Aspirin

Question 48

When may aspirin be used?

Answer 48

After a MI or in coronary artery disease, when there is a risk of MI

Question 49

Why may aspirin be used when there is a risk of MI?

Answer 49

To reduce the risk of platelet rich arterial clots forming

Question 50

Why is hypertension an important cardiovascular condition?

Answer 50

Since it carries the rest of developing cardiovascular disease of stroke

Question 51

What do drugs used in the treatment of hypertension act to do?

Answer 51

Reduce cardiac output and/or peripheral resistance

Question 52

What drugs are used in the treatment of hypertension?

Answer 52

ACE-inhibitors Diuretics Adrenoceptor blocks Ca channel blockers