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

Drugs Acting on the CVS Flashcards

1
Q

What are cardiovascular drugs used to treat?

A 
Arrythmias
Heart failure 
Angina 
Hypertension 
Risk of thrombus formation
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2
Q

What can cardiovascular drugs alter?

A

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

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3
Q

What can cause arrhythmias?

A

Ectopic pacemaker activity
After-depolarisations
Re-entry loop

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4
Q

How can ectopic pacemaker activity lead to arrhythmias?

A

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

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5
Q

What are after-depolarisations?

A

Abnormal depolarisations following the action potential

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6
Q

What are after-depolarisations thought to be caused by?

A

High intracellular Ca

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7
Q

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

A

A longer QT interval

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8
Q

What causes a re-entry loop?

A

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

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9
Q

When will a re-entry loop occur?

A

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

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10
Q

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

A

Atrial fibrillation

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11
Q

What can cause several small reentry loop in the atria?

A

Being stretched over time

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12
Q

What are the basic classes of anti-arrythmic drugs?

A

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

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13
Q

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

A

Lidocaine

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14
Q

What channels does lidocaine block?

A

Voltage gated Na channels

Only those that are in an open or inactive state

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15
Q

How quickly does lidocaine dissociate?

A

Quickly- in time for next AP

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16
Q

What is the advantage of lidocaine?

A

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

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17
Q

Why can lidocaine be used as an anti-arrythmic?

A

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

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18
Q

Give two examples of class II anti-arrythmic drugs

A

Propanolol

Atenolol

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19
Q

How do class II anti-arrythmic drugs work?

A

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

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20
Q

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

A

Beta-blockers

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21
Q

When are beta-blockers used?

A

After a MI

22
Q

What are beta-blockers used after an MI?

A

To combat increases in sympathetic activity

To reduce oxygen demand of myocardium

23
Q

How do class III anti-arrythmic drugs work?

A

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
Q

Why are class III drugs not generally used?

A

Because they can also be pro-arrythmic

25
Q

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

A

Verapamil

26
Q

How do class IV drugs work?

A

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

27
Q

Where is adenosine produced?

A

Endogenously

28
Q

What does adenosine act on?

A

A1 receptors at AV node

29
Q

What kind of receptor are A1 receptors?

A

GPCR

30
Q

What happens on stimulation of A1 receptors?

A

Inhibits adenylyl cyclase

31
Q

How does adenosine work as an anti-arrythmic?

A

It enhances K conductance and hyperpolarises cells of conduction tissue

32
Q

Essentially, what does adenosine do?

A

‘Resets’ the heart

33
Q

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

A

ACE-inhibitors

Diuretics

34
Q

How to ACE-inhibitors treat chronic heart failure?

A

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

35
Q

Why do ACE-inhibitors have a diuretic action?

A

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

36
Q

Why does the inhibition of aldosterone act as a diueretic?

A

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

37
Q

What is the principle of angina treatment?

A

Reducing the work load of the heart

38
Q

What drugs are used to treat angina?

A

ß-blockers

Organic nitrates

39
Q

What drugs improve blood supply to the heart?

A

Organic nitrates

Ca channel blockers

40
Q

How do organic nitrates treat angina?

A

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.

41
Q

What is the primary action or organic nitrates?

A

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).

42
Q

What is the secondary action of organic nitrates?

A

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

43
Q

What do some heart conditions carry?

A

An increased risk of thrombus formation

44
Q

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

A

Atrial fibrillation

Valve disease

45
Q

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

A

Anti-thrombotic drugs

46
Q

Give an example of an anti-thrombotic drug?

A

Warfarin

47
Q

Give an example of an anti-platelet drug?

A

Aspirin

48
Q

When may aspirin be used?

A

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

49
Q

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

A

To reduce the risk of platelet rich arterial clots forming

50
Q

Why is hypertension an important cardiovascular condition?

A

Since it carries the rest of developing cardiovascular disease of stroke

51
Q

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

A

Reduce cardiac output and/or peripheral resistance

52
Q

What drugs are used in the treatment of hypertension?

A

ACE-inhibitors
Diuretics
Adrenoceptor blocks
Ca channel blockers

ESA 2- Cardiovascular System (18 decks)

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