Cardiac arrhythmias Flashcards
How can the normal electrical control of the heartbeat be recorded
Using an ECG
What is an ECG reading made up of
P wave
QRS Complex
T wave
What is the P wave
Atrial contraction
What is the QRS complex
Ventricles contractracting
What is the T wave
Repolarisation of the ventricles after contraction
Which nervous system controls the heart rate
Autonomic nervous system
What effect does the sympathetic nervous system have on heart rate
Increases heart rate and contractility
What effect does the sympathetic nervous system have on heart rate
Slows down heart rate
What can cardiac arrhythmia be divided into
Tachycardia
Bradycardia
What can cardiac arrhythmia be divided into
Tachycardia
Bradycardia
What is Tachycardia
Pulse rate over 100 beats per min
What is bradycardia
Pulse rate les than 60 beats per min
Give examples of tachycardia
- Sinus tachycardia
- Supraventricular tachycardia
- Ventricular tachycardia
- Atrial fibrillation
- Ventricular fibrillation
What is sinus tachycardia
Heart rate of above 100 beats per min with ECG showing a normal P wave before each QRS complex
When does sinus tachycardia occur
Normal response to exercise
What can sinus node disease lead to
Both bradycardia and tachycardia due to malfunction of the Sino atrial node
What is supra ventricular tachycardia
A term used for abnormal tachycardias originating in or above the AV node
Where can supraventricualr tachycardia result from
May arise from the atria where a P wave will still be seen or from the AV node itself
When does a ventricular tachycardia arise
Arises within the ventricle because the electrical impulse spreads from the abnormal focus directly through the heart muscle
What might the ECG of a person suffering from ventricular tachycardia show
A wider than normal QRS complex
What is atrial fibrillation
where the atrial acirtvity becomes completely disorded with constant electrical activity throughout the atria and loss of co ordinated atrial contraction
Describe the ECG of a patietn with atrial fibrillation
No P waves
What can ventricular fibrillation cause
Causes chaotic ventricular activity that can cause a cardiac arrest
Give examples of some bradycardias
- Sinus bradycarida
- Atrio ventricular block
- Sinus node disease
- Cardiovascular reflex disorders
What can sinus bradycardia be caused by
Drugs or hypothyroidism
What is another term for atria ventricular block
Heart block
When does atrioventricular block occur
When conduction of the impulse from the atria to the ventricles is impaired as a result of disease of the AV node or bundle of HIS
What can cadiovasuiclar reflex disorders result in
Syncope due to transient bradycardias
What can arrhythmias present with
Can be asymptomatic or present with:
1. Palpitations
2. Heart failure
3. Syncope
What clinical assessments do you need to make at the time of suspected arrhythmia
- Basic life support
- Pulse
- Blood pressure
- ECG
How are tachycardias usually treated
By drugs such as:
1. digoxin
2. beta blockers
3. Amiodarone
Why is beta blockers given to tachycardias patientss
To control the ventricular rate in atrial fibrillation
Why is digoxin given to tachycardias patients
To control the ventricular rate in atrial fibrillation
Why is Amiodarone given to tachycardias patients
Can sometimes revert atria fibrillation to sinus rhythm
How are drugs used to treat arrhythmia classified
- Can be classified by what they act on
- Classified using the Vaughan Williams classification
How are drugs used to treat arrhythmia classified by what they act on
- Acting on supraventicular arrhythmia
- Acting on supraventricular arrhythmia
- Acting on ventricular arrhythmia
Give an example of an arrhythmia managing drug that acts on supraventicular arrhythmia
Verapamil
Give an example of an arrhythmia managing drug that acts on venticular arrhythmia
Lidocaine
Give an example of an arrhythmia managing drug that acts on supraventicular and ventricular arrhythmia
Amiodarone
What is the Vaughan Williams classification based on
antidysrhythmic action based in class I-IV
Describe class I arrhythmia managing drug
Membrane stabilising drugs
Describe class II arrhythmia managing drug
Beta adrenorecpetors antagnost
Describe class III arrhythmia managing drug
Agents influencing potassium channels
Describe class IV arrhythmia managing drug
Calcium channel blockers
What can class I antiarrhythmics be further divided into?
I a, I b, I c
Depending upon the kinetics of their binding to the sodium channel and their effect on the cardiac action potential
What do class I a drugs do
Prolong the action potential
What do class I b drugs do
Shorten the action potential
What do class I c drugs do
Have little or no effect on the action potential
Talk through the mechanism of action of class I membrane stabilising drugs
They act on sodium channel blockers
this means the binding site for these drugs is only available when the sodium channel is in the open or refractory state
Accessibility to the target is governed by the rate of openign of the channel
Do antiarrhythmic drugs have a greater effect on dysrhythmic or normal hearts? why?
dysrhythmic as the more a channel is open the more likely the drug is to achieve its effect and in dysrhythmic hearts the channels are open more frequently
Give examples of class I membrane stabilising drugs
Procainamide and quinidine
what effect can class I membrane stabilising drugs have on oral structures and dental management
They may produce angioedema that can effect the lips tongue and floor of the mouth
What drug interaction should we be aware of if a patient is on a class I membrane stabilising drugs
- bupivacaine as myocardial depression can occur
- Erythromycin increases the likelihood of ventricular arrhythmia when given with quinidine
- Antifungals should not be prescribed to patients taking quinidine due to risk of ventricular arrythmias
Take through the mechanisms of action for class II beta adrenorecpetors antagonist
These drugs decrease cardiac sympathetic activity by selectivity blocking beta adrenergic receptors
Take through the mechanisms of action for class III agents influencing potassium channels
By blocking potassium channels these drugs prolong repolarisation
what effect can class III agents influencing potassium channels have on oral structures and dental management
Patients on amiodarone may complain of a metallic taste and this drug can produce Thrombocytopenia
What drug interaction should we be aware of if a patient is on a class III agents influencing potassium channels
- Bupivicaine
- Erythromycin increases the risk of ventricular arrhythmias when combines with amiodarone so should be avoided
Take through the mechanisms of action for class IV calcium channel blocker
Acts on non-dihydropyridines verapamil and diltiazem on cardiac L-type calcium channels resulting in slowing of the sino-atrial node pacemaker.
Give one example of cardiac glyocsides
Digoxin
Talk through the mechanisms of action of cardiac glycosides
They inhibit the membrane bound sodium potassium ATPase which result sin an increase in intracellular sodium
As a consequence of this intracellular calcium rises producing an increase in contractility
What impact can digoxin have on oral structures
Can produce a pain solar to trigeminal neuralgia in the lower part of the face
What is digoxin toxicity perciprated by
hypokalaemia
Give examples of drugs in dentistry that can produce hypokalaemia
LA with adrenaline
Amphotercin \
Give examples of drugs in dentistry that can produce hypokalaemia
LA with adrenaline
Amphotercin
Give examples of drugs that can increase the plasma concentration of digoxin
- NSAIDS
- Erythromycin
- Itraconazole
