Arrhythmias

Question 1

What controls the hearts rhythm?

Answer 1

The heart rhythm is controlled via the sinoatrial node which depolarises rhythmically causing depolarisation to surrounding atrial tissue and AVN.

Question 2

What are Arrhythmias and how are they caused?

Answer 2

Arrhythmia are deviations from the normal rhythm caused by disturbances in depolarisation, generation or conduction.

Question 3

What symptoms would a patient suffering from arrhythmias express?

Answer 3

Arrhythmias will cause symptoms such as palpitations, chest pain and breathlessness.

Question 4

What are the two main classes of arrhythmias and how do they differ?

Answer 4

The two classes of arrhythmias are tachy and brady.brady is associated with a slow heart rate and tachy is associated with a fast heart rate.

Question 5

What risk factors increase the occurrence of arrhythmias?

Answer 5

Arrhythmia occurrence is increased with heart failure, heart attack, heart valve disease and inflamed cardiac muscle.

Question 6

In what type of patients is atrial fibrillation more common?

Answer 6

Atrial fibrillation is common in patients with hypertension.

Question 7

What can the occurrence of atrial fibrillation lead to?

Answer 7

Patients with atrial fibrillation may lead to thrombosis caused by unoptimal flow of blood, these clots can travel to cerebral arteries causing ischaemic stroke where anticoagulants may be used.

Question 8

What are the 3 mechanism of arrhythmias?

Answer 8

Accelerated automaticity - fast depolarisation then normal.

Triggered activity - damage causes after depolarisations

Re-entry - depolarisation re entry problems caused by damage to ring of tissue.

Question 9

What occurs if an area of the myocardium is damaged in terms of action potential passing through?

Answer 9

If damaged the tissue won’t conduct normally again and might only conduct in one direction slowly causing reconduction after the action potential has already passed causing a extra/skip of beat.

Question 10

Antiarrhythmic drugs are classified on their effects of action potential. What are the classes?

Answer 10

Class I
A
B
C
Class II
Class III
Class IV

Question 11

What is the main mechanism of action of all antiarrhythmic Class I drugs?

Answer 11

They inhibit sodium channels slowing the rate of depolarisation.

Question 12

Class I antiarrhythmics are subdived based on their effects on the duration of the action potential. Name a drug for each subclass of A to C.

Answer 12

IA - disopyramide
IB - lidocaine
IC - Flecainide

Question 13

What types of channel blockages occur with Class IA use and what effect does this have on the repolarisation?

Answer 13

Class IA block both sodium and potassium channels which prolongs repolarisation.

Question 14

What types of channel blockages occur with Class IB use and what effect does this have on the repolarisation?

Answer 14

They weakly block sodium channels and have no effect on repolarisation but may shorten it.

Question 15

What types of channel blockages occur with Class IC use and what effect does this have on the repolarisation?

Answer 15

The block both marked sodium channels and weak potassium channels and calcium channels and minimal effect on repolarisation.

Question 16

What are the class II antiarrhythmics and what effect do they have?

Answer 16

These are the beta blockers blocking the action of catecholamines on the heart, reduce the rate of depolarisation of the SA and AV node.

Question 17

Give an example of a Class III antiarrhythmic.

Answer 17

Amiodarone and Sotalol.

Question 18

How do class III prolong the duration of action potential?

Answer 18

They block potassium channels involved in repolarisation and increasing refractory periods.

Question 19

What is special about the effects caused by Amiodarone?

Answer 19

The block sodium, potassium and Calcium channels and antagonise alpha and beta adrenoceptors.

Question 20

What are Class IV drugs and how are do they act as an antiarrhythmic?

Answer 20

Class IV drugs are calcium channel blockers which block L-Type calcium ion channels, this slows the conduction of the action potential.

Question 21

There are other antiarrhythmic drugs that are not classified what are these?

Answer 21

Adenosine and Digoxin.

Question 22

How does adenosine work as a antiarrhythmic?

Answer 22

Adenosine cause hyperpolarisation in the AVN slowing nodal conduction by opening potassium channels.

Question 23

How does digoxin work as a antiarrhythmic?

Answer 23

Digoxing stimulates vagal activity releasing ACh which slows heart rate and conduction in AVN and bundle of his