Lecture 14- Drugs And CVS

Question 1

Causes of tachycardia?

Answer 1

Ectopic pacemaker activity

Atrial fibrillation

Re entry loop

Afterdepolarisations

Question 2

Causes of bradycardia?

Answer 2

Conduction block at Sv node or bundle of his

Sinus bradycardia

Question 3

What are after depolarisations?

Answer 3

More likely to occur with high intracellular calcium they result in depolarisation after the action potential and main depolarisation has occurred. Creates oscillations

Question 4

What can cause atrial fibrillation?

Answer 4

Re entrant mechanisms whereby signal goes around circuit it’s not supposed to and can come back on itself

Question 5

What are the four classes of anti arrhythmic drugs?

Answer 5

I- block voltage sensitive sodium channels

II- beta blockers

III- block potassium channels

IV- drugs that block calcium channels

Question 6

How do class 1 drugs work?

Answer 6

Block sodium channels in damaged depolarised tissue and channels in inactive state. Prevents damaged tissue from depolarising spontaneously and from events happening between depolarisations .
Sometimes used after MI

Question 7

Class 2?

Answer 7

Beta blockers used after MI as they reduce oxygen demand and reduce slope of pacemaker potential to slow conduction at av node and heart rate

Question 8

Class 3?

Answer 8

Blocking potassium channels prolongs the action potential and the subsequent refractory period which slows heart rate
Eg amiodarone

Question 9

Class 4?

Answer 9

Calcium channel blockers such as verapamil.

Decreases AV node conduction and cause negative inotropy

Question 10

Adenosine?

Answer 10

Short acting but hyperpolarises cells to prevent APs and so treats tachycardia

Question 11

What can be given to patients that can’t tolerate ace inhibitors?

Answer 11

Angiotensin II receptor blockers such as losartan

Question 12

Diuretics?

Answer 12

Eg furosemide reduce circulating volume

Question 13

Calcium channel blockers?

Answer 13

Work on vascular smooth muscle to reduce TPR and BP eg amlopidine and verapamil which works on heart to reduce contraction force

Question 14

What are positive inotropes?

Answer 14

Cardiac glycosides such as digoxin. Useful short term but long term better off not having heart work so hard

Beta adrenergic agonists like dobutamine

Question 15

How can nitrates be used to treat angina?

Answer 15

Cause vasodilation which reduces preload of the heart. Heart therefore contracts less which reduces its oxygen demand.

Dilates collaterals which helps perfuse tissue also. Has little to no effect on arterioles

Question 16

For what conditions are anti-thrombotic drugs important?

Answer 16

Atrial fibrillation

History of MI

Prosthetic heart valves

Question 17

What are the two classes of anti thrombotic drugs?

Answer 17

Anticoagulants such as heparin and warfarin

Antiplatelet drugs such as aspirin and clopidogrel