CVS 9 (Drugs & the CVS)

Question 1

What are the 3 usual causes of arrhythmia’s?

Answer 1

1) Ectopic pacemaker activity
2) After depolarisations
3) Re-entry loops

Question 2

Name some types of arrhythmia’s:

Answer 2

• Bradycardia
• Atrial flutter
• Fibrillation
• Ventricular tachycardia
• Supraventricular tachycardia

Question 3

Name the 4 classes of anti-arrhythmic drugs:

Answer 3

1) Drugs that block voltage-gated Na+ channels
2) beta-adrenoceptor antagonists
3) Drugs that block K+ channels
4) Drugs that block Ca2+ channels

Question 4

Give an example of a class I anti-arrhythmic drug, and its action:

Answer 4

Lidocaine - blocks voltage-gated Na+ channels

Question 5

What type of anti-arrhythmic drug is Lidocaine?

Answer 5

Class I - Drug that blocks voltage-gated Na+ channels

Question 6

Give an example of a class II anti-arrhythmic drug, and its action:

Answer 6

Propanolol/Atenolol

Beta-adrenoceptor antagonist = decreases slope of pacemaker potential

Question 7

What type of anti-arrhythmic drug is Propanolol?

Answer 7

Class II - Beta-adrenoceptor antagonist

Question 8

Explain Wolff-Parkinson-White syndrome:

Answer 8

Re-entry loop due to an extra conduction pathway causes tachycardia

Question 9

What type of anti-arrhythmic drug is Amiodarone?

Answer 9

Class III - Drug that blocks K+ channels

Question 10

Name the drug which is used to treat tachycardia associated with Wolff-Parkinson-White syndrome:

Answer 10

Amiodarone

Question 11

Give an example of a class IV anti-arrhythmic drug, and its action:

Answer 11

Verapamil

• Blocks Ca2+ channels
• Decreases slope of AP
• Decreases AV nodal conduction
• Decreases force of contraction

Question 12

What type of anti-arrhythmic drug is Verapamil?

Answer 12

Class IV = Drug that blocks Ca2+ channels

Question 13

Which circulating molecule is anti-arrhythmic, by briefly blocking conductance, restoring the sinus rhythm?

Answer 13

Adenosine

Question 14

Define heart failure:

Answer 14

Chronic failure of the heart to provide sufficient output to meet the body’s requirements.

Question 15

Name the 2 types of drugs which can increase cardiac output during heart failure:

Answer 15

1) Cardiac glycosides

2) beta-1 adrenoceptor agonists

Question 16

Give an example of a cardiac glycoside, and explain how it can be used to treat heart failure:

Answer 16

Digoxin/Ouabain
- Inhibits Na+/K+-ATPase
- Reduced activity of NCX
- More Ca2+ stored in SR
= Increased force of contraction (^CO)

Question 17

Give an example of a beta-1 adrenoceptor agonist, and explain how it can be used to treat heart failure:

Answer 17

Dobutamine/Adrenaline/NA

• Increases contractility = Increases cardiac output
• Short-term = used in acute but reversible heart failure, after surgery

Question 18

Name 3 types of drugs which can decrease the workload of the heart during heart failure:

Answer 18

1) ACE inhibitors
2) Beta-adrenoceptor antagonists
3) Diuretics

Question 19

Explain how an ACE inhibitor can be used to treat heart failure:

Answer 19

Prevents formation of Angiotensin II:

• less vasoconstriction = decreases blood pressure = decreased afterload
• less Na+ and H2O reabsorption = less fluid retension = decreased preload

Question 20

Name the 2 types of drugs used to treat AF and/or valve disease:

Answer 20

1) Anticoagulants

2) Antiplatelets

Question 21

Give an example of an anticoagulant, and explain how it is used to treat AF + valve disease:

Answer 21

Heparin (short-term)

• Activates anti-thrombin III = inactivates Thrombin + Factor Xa
• Decreases risk of thrombus formation

Warfarin (long term)
- Inhibits vitamin K reductase
= no production of Factors II, VII, IX + X
- Decreases risk of thrombus formation

Question 22

Give an example of an antiplatelet drug, and explain how it is used to treat AF + valve disease:

Answer 22

Aspirin

• Inhibits cyclo-oxygenase-1
• Prevents formation of Thromboxane (an inducer of platelet aggregation)
• Decreases risk of thrombus formation