Drugs And CVS

Question 1

What is ectopic pacemaker activity?

Answer 1

This is where damaged myocardium becomes depolarised and spontaneously active.

Question 2

What can cause a delayed after-depolarisation?

Answer 2

These can occur when intracellular calcium is high and so a second action potential is initiated.

Question 3

What is an early - after depolarisation?

Answer 3

This is when there are oscillations of membrane potential leading to a prolonged action potential.

Question 4

What happens when there is incomplete conduction damage?

Answer 4

In this case, there is a unidirectional block in part of the myocardium and this leads to a circus of excitation being set up.

Question 5

What causes atrial fibrillation?

Answer 5

Multiple reentrant loops due to damage to the atrial tissue due to over stretching for example.

Question 6

What ion channels can be blocked to help regulate heart rate and rhythm?

Answer 6

K+, Na+ and Ca2+

Question 7

Give an example of a voltage sensitive sodium channel blocker

Answer 7

Lidocaine.

Question 8

When are Na channel blockers of use?

Answer 8

These do not have much effect in normal tissue as they dissociate straight after the action potential, however following MI they prevent ventricular tachycardia

Question 9

Give two examples of B blockers

Answer 9

Atenolol and propanolol

Question 10

What action do B blockers have on the shape of the sino-atrial pacemaker potential?

Answer 10

It decreases the slope and means that it takes longer to reach threshold

Question 11

State two situations in which B blockers can be used.

Answer 11

In supra ventricular tachycardias as there is slowing of AV node conduction, and post MI to reduce sympathetic activity on the heart and therefore reduce ischaemia.

Question 12

What action do K+ channel blockers have on the action potential in the heart?

Answer 12

These prolong the action potential as repolarisation takes longer which means that Na channels remain inactivated and this means it is longer before the next action potential is fired.

Question 13

What is the only situation which K+ channel blockers are used?

Answer 13

Amiodarone, which treats tachycardia in Wolff-Parkinson White syndrome.

Question 14

What is the action of Ca channel blockers on the heart?

Answer 14

These decrease theSA node action potential slope and decrease AV node conduction and force of contraction.

Question 15

Where do dihydropyridines ca channel blockers work?

Answer 15

These only act on smooth muscle.

Question 16

Where in the heart does adenosine work?

Answer 16

It acts on a1 receptors at the AV node, and enhances K+ conductance and is an anti-arrhythmic.

Question 17

In heart failure , we want drugs which have what affect on the heart?

Answer 17

We want to increase cardiac output so we want inotropic drugs.

Question 18

How do cardiac glycosides work?

Answer 18

Digoxin: this blocks the sodium potassium pump leading to an increase in intracellular sodium and therefore increased NCX function and increased calcium - higher force of contraction.

Question 19

What is the affect of cardiac glycosides on the Vagal system?

Answer 19

These stimulate the Vagal system and so lead to slower AV conduction and therefore a slower heart rate.

Question 20

What drugs can be used to increase short term outcome of the heart in acute heart failure or cardiogenic shock?

Answer 20

B adrenoceptor agonists can be used to increase cardiac output.

Question 21

What are the functions of angiotensin II?

Answer 21

It is a vaso-constrictor and it also increases reabsorption of sodium at the kidney and therefore water retention.

Question 22

Name three drugs which reduce workload on the heart.

Answer 22

Diuretics, ACE inhibitors and b blockers.

Question 23

How can we treat angina?

Answer 23

We want to lower workload of the heart, and improve blood supply. We use B blockers, Ca channel antagonists, organic nitrates.

Question 24

Where do organic nitrates work?

Answer 24

These act on smooth muscle, causing vasodilation.

Question 25

Which vessels are most effected by the use of organic nitrates?

Answer 25

The venous system followed by the coronary arteries.

Question 26

What is the cellular action of organic nitrates?

Answer 26

No- acts on guanylate cyclase, and this leads to an increase in cGMP and a decrease in Ca2+, thus causing smooth muscle relaxation.

Question 27

What type of arteries does NO act on in the heart to increase blood supply?

Answer 27

Collateral arteries.

Question 28

What are the two types of antithrombotic drugs available?

Answer 28

Anticoagulants and antiplatelet

Question 29

Give an example of anticoagulant drugs

Answer 29

Heparin - inhibits thrombin

Warfarin - antagonises vitamin K preventing clotting

Question 30

What type of drug is aspirin?

Answer 30

Antiplatelet

Question 31

What are the drug targets for treating hypertension?

Answer 31

Decrease Cardiac output, decrease TPR, decrease blood volume

Question 32

What drugs can be used to treat hypertension?

Answer 32

ACE inhibitors, diuretics, Ca SM channel blockers, a1 adrenoceptor antagonists.