Arrythmias Flashcards
what are the shockable cardiac arrest rhythms?
ventricular tachycardia
ventricular fibrillation
what are the non-shockable cardiac arrest rhythms?
asystole = no significant electrical activity
pulseless electrical activity = all electrical activity except VT/VF, including sinus rhythm without a pulse
what is narrow complex tachycardia?
fast heart rate w
QRS complex duration less than 0.12s (3 small squares on ECG)
what are the main differentials of a narrow complex tachycardia?
sinus tachycardia
supraventricular tachycardia
atrial fibrillation
atrial flutter
what does the treatment of sinus tachycardia focus on?
the underlying cause
what is supraventricular tachcardia treated with?
vagal manoeuvres
adenosine
what is atrial fibrillation treated with?
rate control
rhythm control
what is atrial flutter treated with?
rate control
rhythm control
what is broad complex tachycardia?
fast heart rate w
QRS complex duration more than 0.12s (3 small squares)
what are the differentials of broad complex tachycardia?
ventricular tachycardia or unclear cause
polymorphic ventricular tachycardia - torsades des pointes
atrial fibrillation with bundle branch block
supra ventricular tachycardia with bundle branch block
how is ventricular tachycardia or unclear cause of broad complex tachycardia treated?
IV amiodarone
how is polymorphic ventricular tachycardia (torsades des pointed) treated?
IV magnesium
how is atrial fibrillation with bundle branch block treated ?
same as AF
rate or rhythm control
how is supra ventricular tachycardia with bundle branch block treated?
same as SVT
vagal manoeuvres and adenosine
what are life threatening feautures of tachycardia and what are patients with these treated with?
syncope (loss of consciousness), heart muscle ischaemia (chest pain) shock or severe HF
treated with synchronised DC cardioverison under sedation or general anaesthesia
IV amiodraone added if DC shocks unsuccessful
what normally happens to an electrical signal passing through the atria?
passes through once
stimulates contraction
disappears through AV node
what is atrial flutter caused by?
a re-entrant rhythm in either atrium
an extra electrical pathway in the atria causes the electrical signal to re-circulate in a self-perpetuating loop
therefore the signal goes round and round the atria without interruption
what is the usual atrial rate in atrial flutter?
300 bpm
in atrial flutter does the electrical signal enter the ventricles on every loop?
no
because of the long refractory period of the AV node
leads to 2 atrial contractions for every ventricle contraction - ventricle 150bpm
how does atrial flutter appear on an ECG?
sawtooth appearance
repeated P waves at around 300bpm with narrow complex tachycardia
what is the treatment of atrial flutter?
similar to AFib
anticoagulation based on CHA2DS2-VASc score
radiofreuency ablation of re-entrant rhythm can be permanent solution
what is the QT interval?
from the start of the QRS complex to the end of the T wave
what does the corrected QT interval (QTc) estimate?
the QT interval if the heart rate were 60bpm
when is the QT interval prolonged in men?
more than 440 milliseconds
when is the QT interval prolonged in women?
more than 460 milliseconds
what is depolarisation?
the electrical process that leads to heart contraction
what is repolarisation?
a recovery period before the muscle cells are ready to depolarise again (contraction)
what does a prolonged QT interval represent?
prolonged repolarisation of the myocytes (heart muscles) after a contraction
what can waiting for a long time for a repolarisation result in?
spontaneous depolarisation in some muscle cells before repolarisation
known as afterdepolarisations
what do afterdepolarisations do
and what can this lead to?
afterdepolarisations spread throughout the ventricles causing a contraction before proper repolarisation
when this leads to recurrent contractions without normal depolarisations this is known as torsades des pointes - types of polymorphic VT
what does torsades des pointes look like on an ECG?
standard ventricular tachycardia but looks as though the QRS complex is twisting around the baseline
height of QRS complex gets progressively smaller, then larger, then smaller, etc
what does torsades des pointes become?
it will either spontaneously terminate and revert to normal sinus rhythm
or progress to ventricular tachycardia which can lead to cardia arrest
what are the causes of prolonged QT syndrome?
long QT syndrome (inherited condition)
medications - antipsychotics, citalopram, flecanide, stall, amiodraone, macrolide antibiotics
electrolytes imbalances - hypokalaemia, hypomagnesaemia, hypocalcaemia
what is the management of prolonged QT syndrome?
stopping and avoiding medications that cause it
correcting electrolyte imbalances
beta blockers - not sotalol
pcaemaerks or implantable cardiac defibrillators
what is the acute management of torsades des pointes?
correcting underlying cause - electrolyte imbalances, medication
magnesium infusion - even if serum magnesium normal
defibrillation if ventricular tachycardia occurs
what is ventricular ectopics?
premature ventricular beats
what are ventricular ectopics caused by?
random electrical discharges outside the atria
what do patients with ventricular ectopics often complain of?
random extra or missed heat beats
who is ventricular ectopics more common in?
relatively common at all ages and in healthy patients
more common w pre-exiting heart conditions - ischaemic heart disease or heart failure
how does ventricular ectopics appear on an ECG?
isolated, random, abnormal, broad QRS complexes on an otherwise normal ECG
what is bigeminy?
when every other beat is a ventricular ectopic
how does bigeminy appear on an ECG?
normal beat, immediately followed by an ectopic beat, normal beta, ectopic beat etc
what does management of ventricular ectopics involve?
reassurance and no treatment in otherwise healthy people with infrequent ectopics
specialist advice for the with underlying heart disease, frequent or concerning symptoms (chest pain or syncope) or family history of heart disease or sudden death
beta blockers sometimes used to manage symptoms
what causes first degree heart block?
delayed conduction through the AV node
every atrial impulse still leads to a ventricular contraction
therefore every P wave is followed by a QRS complex
how does first-degree heart block present on an ECG?
PR interval greater than 0.2s (5 small or 1 big square)
what causes second-degree heart block?
when some atrial impulses do no make through the AV node to the ventricles
some P waves not followed by QRS complexes
what are the types of second-degree heart block?
mobitz type 1 - Wenckebach phenomenon
mobitz type 2
what is second-degree heart block mobitz type 1?
where the conduction through the AV node takes progressively longer until it finally fails after which it resets
how does second-degree heart block mobitz type 1 present on an ECG?
an increasing PR interval until a P wave is not followed by a QRS complex
PR interval then returns to normal and cycle repeats itself
what is second degree heart block mobitz type 2?
where there is intermittent failure of conduction through the AV node
what is this degree heart block?
complete heart block
there is no observable relationship between the P waves and QRS complexes
what is there a risk of with second degree heart block mobitx type 2?
asystole
how does second degree heart block mobitx type 2 look on an ECG?
absence of QRS complexes following P waves
usually a set ratio of P waves to QRS complexes
PR interval remains normal
when can it be difficult to tell if t is mobitz type 1 or 2 second degree heat block?
when there is a 2:1 block
2 P waves for every QRS complex
every other P wave does not stimulate a QRS complex
what is there a significant risk of with this degree heart block?
asystole
what is bradycardia?
slow heart rate
typically less than 60bpm
can be under 60 in normal fit healthy patients without causing any symptoms
what are some causes of bradycardia?
medications - beta blockers
heart block
sick sinus syndrome
what is sick sinus syndrome?
it encompasses many conditions that cause dysfunction in the SA node
what is sick sinus syndrome often caused by?
idiopathic degenerative fibrosis of the SA node
what can sick sinus syndrome result in?
sinus bradycarida
sinus arrythmias
prolonged pauses
what carries a risk of asystole?
mobitz type 2
third degree/complete heart block
previous asystole
ventricular pauses longer than 3s
what is the management of unstable patients and those at risk of systole?
IV atropine - first line
inotropes - isoprenaline or adrenaline
temporary cardiac pacing
permanent implantable pacemaker - when available
what are options of temporary cardiac pacing?
transcutaneous pacing - using pads on patients chest
transvenous pacing - using a catheter fed through the venous system to the heart directly
what type od medication is atropine?
antimuscarinic
how does atropine work?
by inhibiting the parasympathetic nervous system
leads to side effects of pupil dilation, dry mouth, urinary retention, constipation
