9 Drugs of the CVS

Question 1

What is an arrhythmia?

Name 3 kinds of arrythmia

Answer 1

An abnormality of heart rate or rhythm

Atrial fibrillation, bradycardia, tachycardia, atrial flutter, ventricular fibrillation

Question 2

List 2 causes of arrythmias

Answer 2

Ectopic pacemaker activity- damaged area of tissue fires action potentials faster than the SAN
Afterdepolarisations- abnormal depolarisations after the action potential

Question 3

When is a delayed after-depolarisation more likely to happen?

Answer 3

If the intracellular Ca2+ concentration is high

Question 4

How can an early afterdepolarisation be seen on an ECG?

Answer 4

Long QT interval.

Question 5

What is a re-entry loop?

Answer 5

If there is a blockage in a neurone, the action potential takes a longer way around to depolarise the tissues. It can end up depolarising the wrong way.

Question 6

What do re-entry loops cause?

Answer 6

Conduction delays
Accessory pathways
Atrial fibrillation

Question 7

What is a Class I drug? Give an example

Answer 7

Drugs which block voltage-dependent Na+ channels

Lidocaine

Question 8

What is a Class II drug? Give an example

Answer 8

B-adrenoreceptor blocker

Propranolol

Question 9

How do Class II drugs decrease heart rate?

Answer 9

Increase the length of the funny current.

Question 10

What is a Class III drug? Give an example

Answer 10

Drugs which block K+ channels

Sotalol

Question 11

How do Class III drugs work?

Answer 11

Action potential is prolonged by blocking the K+ channels. The absolute refractory period is lengthened preventing many action potentials in a short amount of time

Question 12

What is a Class IV drug? Give an example

Answer 12

Drugs which block Ca2+ channels

Verapamil

Question 13

How do Class IV drugs work?

Answer 13

They decrease the slope of the pacemaker action potential at the SA node. The force of contraction is reduced. There is also some peripheral vasodilation.

Question 14

How does Adenosine work?

Answer 14

Acts on A1 receptors in the AV node. It enhances K+ conductance and hyperpolarises cells of the conducting tissue.

Question 15

List 4 ways drugs can effect the CVS?

Answer 15

Alter the rate and rhythm of the heart
Alter the force of contraction
Alter peripheral resistance and blood flow
Alter blood volume

Question 16

What is heart failure?

Answer 16

Reduced heart contraction

Reduced cardiac output- does not meet body’s needs

Question 17

What do cardiac glycosides do? Give an example

Answer 17

Increase myocardial contractility

Digoxin

Question 18

How do cardiac glycosides work?

Answer 18

Block Na/K ATPase. Build up of Na+ in the cell. Na-Ca-exchanger decreases in activity and so Ca2+ levels increase. More Ca2+ is stored in the S/ER. On depolarisation, more Ca2+ can be released from intracellular stores causing a larger contraction.

Question 19

What do B-adrenoreceptor agonists do? Give an example

Answer 19

Increase myocardial contractility

Dobutamine

Question 20

What is an ACE-inhibitor? How do they work?

Answer 20

Drugs which reduce the workload of the heart.
Angiotensin I cannot be converted to angiotensin II. Angiotensin II is a vasoconstrictor that works in the kidneys. Less water is reabsorbed so the blood pressure and blood volume decreases.

Question 21

What is angina?

Answer 21

Chest pain usually with exertion.

Question 22

Name drug types that can be used to treat angina

Answer 22

B-adrenoreceptor blockers
Ca2+ channel antagonists
Organic nitrates

Question 23

How do organic nitrates work in the CVS?

Answer 23

React with thiols (-SH) in vascular smooth muscle to release (NO2)-. It is then reduced to NO which is a powerful vasodilator.
Guanylate cyclase is activated. Increased cGMP. [Ca2+]i lowered. Muscle relaxes.

Question 24

Where can organic nitrates NOT dilate? Where do they dilate instead to increase blood flow to an ischaemic area?

Answer 24

Arterioles

Collateral arterioles

Question 25

What do antithrombotic drugs do?

Answer 25

Reduce the risk of thrombus formation

Question 26

Name 2 types of antithrombotic drugs. Give an example for both

Answer 26

Anticoagulants- heparin, warfarin

Antiplatelet drugs- aspirin

Question 27

Name 2 drug types used to treat hypertension

Answer 27

ACE-inhibitors

B-blockers