Drugs acting on the heart

Question 1

What is angina pectoris?

Answer 1

Crushing pain that may radiate to the left arm, neck and shoulder
Secretes potassium, H+, bradykinin, adenosine
Results from cardiac ischaemia

Question 2

Glyceryl Trinitrate (GTN)/ Propranolol

Answer 2

Dilate peripheral blood vessels, so that the heart doesn’t have to work as hard and less blood is returned therefore lower force of contraction
Administered orally, sublingually, spray, patches
Used to treat angina and heart attacks

Question 3

Atenolol

Answer 3

Beta-blocker that acts on beta 1 adrenoceptors in the heart
Heart contractions slow down, decrease oxygen, ischaemia is relieved
Used to treat angina

Question 4

Digoxin

Answer 4

Used to treat heart failure and rhythm disorders
Increases cardiac output
Increases force of contraction without increasing oxygen consumption
Decreases need for hospitalisation

Question 5

Classification of dysrhythmias

Answer 5

Site of origin:
- atrial
- junctional (super ventricular) 
- ventricular
True arrhythmias:
- a very disorganised rhythm
Tachycardia's:
- heartbeat is too fast
Bradycardia's:
- heartbeat is too slow

Question 6

List 4 dysrhythmic mechanisms

Answer 6

Ectopic pacemakers:
- cardiac tissue other than SAN initiates heart beat
Delayed after-depolarisation:
- build up of calcium in cells leads to train of action potentials
Re-entry circuits:
- tissue damage/abnormality causes action potentials to travel in circles
Congenital abnormalities:
- additional conducting pathways between atria and ventricles
Heart block:
- damage to conducting pathways disrupts atrial-ventricular signaling

Question 7

People at risk of dysrhythmias

Answer 7

Coronary heart disease
Heart valve disorders
Blood chemistry disorders
Caffeine
Cocaine
Beta-blockers
Amphetamines
Psychotropic
Sympathomimetic

Question 8

What is ventricular fibrillation?

Answer 8

Caused by development of ventricular ectopic circuits
Ventricles cease beating in a co-ordinated way
No QRS waves
Rapidly fatal
DC electrical shock the only way of restoring contractions

Question 9

Classification of anti-dysrhythmic drugs by clinical utility

Answer 9

Drugs for dysrhythmias of supra-ventricular origin:
- adenosine, verapamil
Drugs for dysrhythmias of either supra-ventricular/ventricular origin:
-amiodarone, flecainide, propranolol, quinidine
Drugs for dysrhythmias of ventricular origin:
- lidocaine