Arrythmias: Pathophysiology, Presentation and Investigations Flashcards
What are the three ways in which an abnormal heart rhythm can arise?
automaticity
re - entry
triggered activity
Explain how sinoatrial node, AV node and Purkinje fibres have automacticity?
if you leave them alone- they will trigger by themselves
Why is the sinoatrial node in control?
it’s automaticity is the fastest- heart rate of about 60 bpm
Automaticity of AV node?
45 bpm
Automaticity of ventricles?
35 bpm
What can provoke sinus tachycardia?
fever , thyrotoxicosis and exercise
What is sinus tachycardia?
heart rate shoots up very fast
What can provoke sinus bradycardia?
hypothyroidism
SA node disease/ chonotropic incompetence
What is sinus bradycardia?
slowing of heart rate
What is focal atrial tachycardia?
another area of atria with abnormal heart rhythm
What is re-entry ?
re- entry is caused by a short circuit (created by two different pathways- separate from each other and usually have different properties)
typically
path 1: slow conduction, short refractory period
path 2: rapid conduction, long refractory period
What do the two pathways surround?
for e.g. a valve that doesn’t conduct or a bit of scar from heart attack
What happens when electrical impulse enters the pathway?
it goes down fast pathway and back up slow pathway . Then stops as no more tissue to depolarise
What will happen if timing is perfect?
re-entry is created. The impulse will continue going around the circuit until it is interrupted.
What are supraventricular tachycardia?
fast rhythms coming from the top chambers
What is atrial flutter?
circuit that goes around the tricuspid valve and involves right atrium
What is AV nodal re-entry tachycardia?
is in top left where the entire circuit is within the centre of the heart within the AV node.
Individual born with slow and fast pathway
What is AV re-entry tachycardia?
accessory pathway
abnormal connection between top and bottom that allows that circuit to create.
Goes down through the AV node through the bottom chambers and it should then just stop but in 1 in 300 people has a way back up to the top through an extra connection.
What is triggered activity?
impulse initiations caused by ‘ after depolarisations’
membrane potential oscillations occurring during or immediately after an action potential
If threshold potential is reached a new AP is generated
this can lead to self sustaining tachycardia
Triggered activity examples?
Torsades de pointes
VF
VT
What are the common arrythmias?
atrial fibrillation
atrial flutter
supra ventricular tachycardia
ventricular tachycardia
ventricular fibrillation
complete heart block
Give features of atrial fibrillation?
-common in elderly
-common cause of stroke
- top chamber uncoordinated and therefore bottom chamber goes very quickly and in an irregular fashion
-top chamber wobbling is risk factor for blood clots forming
symptoms are palpitations, breathlessness, fatigue and dizziness
What is the management of atrial fibrillation?
stroke and symptoms management first
Does person with AF need to be on a blood thinner?- CHADSVA score
For symptoms:
rate control- beta blockers, calcium channel blockers , digoxin
rhythm control- drugs (amiodarone, flecainide), ablation
ECG of AF?
irregularly irregular
there are no definite p waves
Features of Atrial Flutter?
- top chamber going really fast like 300 bpm
-risk of blood clots
Why is atrial flutter easier to treat?
re entry circuit and goes round tricuspid valve
Management for atrial flutter?
ablation catheter into heart
try slow down and out of rhythm
Atrial flutter ECG?
regular both in top chambers and bottom chambers
bottom have saw toothed pattern
Give features of supraventricular tachycardia?
- means fast heart from above the ventricle
-includes AVNRT, AVRT and focal AT
-does not include sinus tachycardia, AF, flutter
-not life threatening but causes symptoms
Describe ECG of supraventricular tachycardia?
regular, usually narrow complex
How is SVT treated?
amenable to catheter ablation
treated acutely with intravenous adenosine
What is Wolf Parkinson white syndrome?
extra connection between top and bottom where electricity can go from top to bottom
Describe ECG of SVT?
short PR interval
delta wave (slurred upstroke to QRS)
Give features of Ventricular Tachycardia?
-cause of shockable cardiac arrest (along with VF)
-people can have and feel ok or can be associated with losing all output
-commonest cause is scarring in bottom chambers
Treatment for VT?
drugs to reduce occurrence
defibrillators
VT ECG?
regular broad complex tachycardia
Give features of VF?
bottom chambers uncoordinated
cant have pulse with VF
Treatment of VF?
drugs to reduce recurrence (beta blockers, amiodarone)
VF survivors usually fitted with an ICD
Give features of complete heart block (3rd degree)?
commonest cause is age related disease of AV node
can have normal atria and ventricles but can have damage in AV node between the two- giving heart block
no electrical connection between atria and ventricles
ECG of complete heart block?
P waves, QRS complexes with no relationship between them
Treatment of complete heart block?
permanent pacemaker
Distinguishing between ECGs of first, second and third degree heart block?
first- length between p wave and QRS long
second (I) - length between p wave and QRS increasing
second (II)- only letting every third p wave through
complete- absoloutely NO relationship
What is sinus pause?
sinus node just fails
What does presentatio n of arrythmia depend on?
blood pressure during arrhythmia and
how long arrythmia lasts
VT/Vf presentations?
blood pressure zero or very low
- cardiac arrest
-drop dead
Sudden bradycardia presentation? (gaps in ECG)
syncope, collapse, faint
AV/ SVT/ flutter presentations?
dizziness, palpitations, breathlessness
AF/ flutter presentation?
can be asymptomatic , esp in elderly
Investigations for PERSISTENT arrythmia?
12 lead ECG
others:
echo (maybe with cardiac MRI)
bloods (thyroid function , cardiac enzymes)
coronary imaging
EP study
Investigations for paroxysmal arrythmia? (episodes)
24 hour ECG (Holter)
event recorder (2-6 weeks
AliveCor - patient purchased
Loop recorder- implanted on chest wall
