Tachyarrhythmias Flashcards
What is an arrhythmia?
An abnormality of cardiac rhythm
What can arrhythmias cause?
Sudden death Syncope Dizziness Palpitations Asymptomatic
What are the two broad categories of arrhythmias?
Describe them briefly!
Bradycardia: slow HR, less than 60 bpm
Tachycardia: fast HR, more than 100 bpm
What categories can tachycardias be subdivided into?
Describe them!
Supraventricular tachycardias (SVT) - arise from the atria or atrioventricular junction
Ventricular tachycardias
- arise from the ventricles
What is meant by sinus rhythm?
Rhythm controlled by the sinus node!
What is the normal cardiac pacemaker?
The sinus node
What is the sinus node?
What controls it?
A collection of cells found in the upper wall of the RA
It is the main pacemaker of the cell
It is controlled by the autonomic nervous system
What is sinus arrhythmia?
Arrhythmia caused by changes in the sinus rhythm, specifically the sinus discharge rate
What is sinus tachycardia?
Is it necessarily a bad thing?
Increase in sinus rhythm causing an increase in heart rate
No, it occurs naturally in response to exercise + excitement
It also occurs in response to fever, anaemia, heart failure, acute PE, and many more
What causes an arrhythmia? There are two mechanisms.
Cardiac rhythm not being generated correctly by SAN
Cardiac rhythm id generated correctly by SAN but is not conducted properly through the heart
What is re-entry?
Don’t describe
A process that occurs in the heart that is the cause of many types of arrhythmia
Involves the formation of abnormal electrical circuits in the heart
Describe what re-entry is, use the AV node as an example.
There are 2 pathways in the AVN, imagine a diamond shape, the pathways are on each side
- slow, with short refractory time
- fast, with long refractory time
In re-entry, the fast pathway gets transiently blocked, because a premature impulse from the SA node has meant the fast pathway is in its repolarisation phase so can’t be depolarised
No impulses can travel down the pathway but the tissue is still excitable
Impulses travel down the slow pathway as normal, but when they get to the apex (where fast and slow meet) the impulses start to travel back up the fast pathway in the wrong direction
You get retrograde conduction up the fast pathway, creating a re-entry circuit
This leads to arrhythmias
In which node do re-entry circuits form?
AV node
What are ectopic beats?
Electrical disturbances that arise from tissue that is not part of the usual heart conduction system
Can be ventricular or atrial
Cause benign, non-sustained arrythmias
A patient complains of feeling missed heart beats, that feel a bit like a heart hiccup. What does this sound like?
Ectopic beats
What is the difference between a narrow and broad complex tachycardia?
Narrow: ventricles are depolarised by the Purkinje fibres still (narrow QRS complex)
Broad: ventricles are not depolarised by the Purkinje fibres (broad QRS complex)
Describe the electrical conduction of the heart?
Impulse generated by SAN
Travel down internodal pathways causing atrial depolarisation
Impulse reaches AVN
Down AV bundle
Down either R or L bundle branch
Into Purkinje fibres causing ventricular depolarisation
Name 4 supraventricular tachyarrhythmias?
Atrial fibrillation
Atrial flutter
AVNRT: atrioventricular nodal re-entry tachycardia
AVRT: atrioventricular re-entry tachycardia
What is atrial fibrillation?
The SA node is conducting impulses irregularly
Causing the atria to not contract properly
And, some (not all) of the chaotic SA impulses are conducted to the ventricles, causing an irregular heartbeat
What does an ECG of atrial fibrillation look like?
Irregularly irregular chaotic heart rhythm
No P waves visible
QRS complexes appear normal but they occur irregularly
Name and describe 3 types of atrial fibrillation?
Paroxysmal: spontaneous termination within 7 days
Persistent: not self-resolving, needs treatment by cardioversion
Permanent: long standing, over 1 year, not treatable by cardioversion
List some causes of atrial fibrillation?
Hypertension CHD Valve disease Hyperthyroidism Idiopathic
Clinical features of atrial fibrillation?
Asymptomatic Palpitations Dyspnoea Syncope Stroke
Why does atrial fibrillation cause strokes?
The blood in the atria becomes stagnant in the atria because the fibrillation means it can’t be pumped out properly
Stagnant blood forms clots
Complications of atrial fibrillation?
Stroke or other clotting problem
Heart failure
Cardiomyopathy
Investigations of arrhythmias in general?
ECG
Bloods: including coagulation
CXR
ECHO
Management of atrial fibrillation?
HR control: beta blockers or sodium channel blocker (verapamil)
Rhythm control: electrical or chemical cardioversion
Thromboprophylaxis: warfarin, apixiban
What is atrial flutter?
Extremely fast atrial heart rate caused by re-entry circuits
The AV node conducts some but not all of the impulses from SAN to the ventricles
What is meant by 2:1 atrial flutter
Atrial flutter
Where the AV node is able to conduct every other impulse from the SAN to the ventricles
What is meant by 3:1 atrial flutter?
Atrial flutter
Where the AV node is only able to conduct every 1 in 3 impulse from the SAN to the ventricles
What would the ECG of atrial flutter look like?
Extremely fast atrial heart rate of about 300
Saw tooth pattern
Rapid, regular P waves
Causes of atrial flutter?
CHD
Atrial dilatation
Hypertension
Obesity
Presentation of atrial flutter?
Palpitations Dyspnoea Syncope Heart failure Stroke
Management of atrial flutter?
Cardioversion
Thromboprophylaxis
Ablation of the part of the heart causing the arrhythmia, the re-entry circuit
What does AVNRT stand for?
Atrioventricular nodal re-entry tachycardia
What is AVNRT?
An accessory conduction pathway arises in the heart, between the atrium and the AVN
Re-entry circuit is created causing arrhythmia
Causes of AVNRT?
Idiopathic, usually occurs in young adults, especially females
What would the ECG of AVNRT look like?
Rapid but normal QRS complexes
Followed immediately by P waves, caused by the retrograde excitation of the atria from the re-entry circuit
Presentation of AVNRT?
Palpitations Chest pain Syncope Dyspnoea Neck pulsation
Management of AVNRT?
Adenosine: can block the AV node so blocking the abnormal impulses from getting to ventricles
Ablation
Medication: beta blockers, calcium channel blockers
What does AVRT stand for?
Atrioventricular re-entry tachycardia?
What is AVRT?
An accessory conduction pathway arises connecting the atria to the ventricles
Re-entry circuit is formed causing arrhythmia
What complications can arise from AVRT? How does it occur?
Wolff-Parkinson White syndrome
When the re-entry circuit begins to travel in both directions
What causes Wolff-Parkinson White syndrome?
A congenital abnormality
Presentation of AVRT?
Palpitations
Syncope
Dizziness
What are the usual causes of ventricular tachycardias?
Ischaemic heart disease
Heart failure
Congenital cardiomyopathies and structural heart defects
List some ventricular tachycardias?
Ventricular fibrillation
Ventricular tachycardia
Torsade de pointes
Premature ventricular contractions
Is premature ventricular contraction a narrow or broad complex tachycardia?
Broad, because the contraction of the ventricles is not caused by the Purkinje fibres
Caused by ectopic beats arising in the ventricles
What is premature ventricular contraction?
Ventricular ectopic beats cause abnormal ventricular contraction
Contraction is slower than usual
These ectopic beats can occur randomly or in patterns
What would an ECG of premature ventricular contraction look like?
Premature broad QRS complexes
They can occur as a one off, or every other beat, or in patterns
Management of premature ventricular contraction?
None needed!
What is ventricular tachycardia (as a specific condition)?
A run of successive ventricular ectopic beats
That take the heart rate above 100bpm
Non-sustained = lasts less than 30 seconds
Sustained = lasts more than 30 seconds
Non-sustained vs sustained ventricular tachycardia?
Non-sustained: the ectopic beats last less than 30 seconds
Sustained: the ectopic beats last more than 30 seconds
What does the ECG of ventricular tachycardia (as a specific condition) look like?
Broad, odd looking QRS complexes that are all of the same shape
Like this: /\/\/\/\/\/\
Occasional P waves are seen super-imposed onto the QRS complexes
Presentation of ventricular tachycardia (as a specific condition)?
Syncope Dyspnoea Angina Compromised CO V-fib Death
Management of Ventricular tachycardia?
Cardioversion
What is Torsades de Pointes?
Episodes of tachycardia interspersed with periods of bradycardia
Causes of Torsades de Pointes?
Long QT: congenital channelopathy
Drugs
Torsades de Pointes involves periods of tachycardia interspersed with periods of bradycardia
What are the risks that occur with each?
During the tachycardic sections there is a risk of going into V-fib and death
During the bradycardic sections you develop long QT which carries a risk of death as well
What would an ECG of Torsade de Pointes look like?
Varying amplitude of QRS
And varying width, indicating the tachy and bradycardic periods
Waxing and waning of QRS amplitude and width
Management of Torsade de Pointes?
Correct the underlying cause
If congenital, use beta blockers and implantable defibrillator
What is ventricular fibrillation?
Rapid, chaotic rhythm of ventricular contraction
Resulting in no CO, and often death if not treated quick enough
What would an ECG of V-fib look like?
Chaotic ventricular rhythm characterised by irregular wavelets of electrical contraction
No QRS complexes due to no ventricular contraction
Management of V-fib?
Urgent cardioversion
Drugs, implantable pacemaker
What does a delta wave look like on an ECG?
What pathology does it indicate?
A convex shape to the QR line
Indicates Wolff-Parkinson White syndrome
What is pulseless ventricular tachycardia?
- HR greater than 180bpm
- A very wide QRS complex.
- Patient is pulseless
- The rhythm originates in the ventricles
Treatment of pulseless ventricular tachycardia?
Cardioversion
