Arrhythmias Year 3 Flashcards
What are shockable rhythms?
Ventricular tachycardia
Ventricular fibrillation
What are non shockable rhythms?
pulseless electrical activity
Asystole
What is Pulseless electrical activity?
All electrical activity except VT/VF without a pulse `
risk factors for asystole
- previous asystole
- ventricular pauses >3seconds
- mobitz type 2
- complete heart block
Management of unstable patients at risk of asystole
- IV atropine (first line)
- inotropes e.g. adrenaline
- temporal cardiac pacing
- permanent implantable pacemaker
Mechanism of action of atropine
antimuscarinic
inhibits parasympathetic nervous system
Adverse drug reactions of atropine
anticholingeric side effects:
- dry mouth
- urinary retention
- constipation
- blurred vision
What is bradycardia?
Heart rate <60bpm
What are the types of bradycardia?
- Absolute: <40bpm
- Relative: when Hr is inappropriately slow for Haemodynamic state of patient
What can sinus node dysfunction cause?
Sinus bradycardia
sick sinus syndrome
Sinus arrest
Part of vasovagal syncope
what is sick sinus syndrome?
- encompasses many conditions that cause SAN dysfunction
- often caused by idiopathic degenerative fibrosis of SAN
- can cause sinus bradycardia, sinus arrhythmias + prolonged pauses
What can cause sinus bradycardia?
- sinus node dysfunction
- medication e.g. beta blockers
- hypothyroidism
- hypothermia
- sleep apnoea
First line drug treatment of bradycardia?
IV atropine 500mcg
Normal PR interval
120-200ms (1 big square)
Normal QRS length
Up to 120ms
(3 small squares)
Normal QTc
400-440ms or 2 large squares
Types of heart block (AV block)
- first degree: prolonged PR interval >200ms (1 big box)
- Mobitz type I: progressive lengthening of PR interval followed by dropped QRs
- Mobitz type II: constant PR interval, random QRS dropped
- complete/third degree: no relationship between p waves + QRS complexes
What medications can cause heart block?
Adenosine
digoxin
opioids
lithium
B blockers
CCBs
what is first degree heart block?
prolonged PR interval
>200ms (1 big box)
what is second degree heart block Mobitz type 1?
progressively longer PR interval followed by dropped QRS
resets + repeats
what is second degree heart block Mobitz type 2?
constant normal PR intervals with random dropped QRS
what is 3:1 block?
ratio of 3 p waves to one QRS
what is 2:1 block?
ratio of 2 p waves to one QRS
what is complete heart block?
no relationship between P waves + QRS complex
What are the narrow complex tachycardias?
QRS <120ms (3 small squares)
- sinus tachycardia
- SVT
- AF
- atrial flutter
Describe atrial flutter
- narrow spectrum tachycardia (QRS <120ms)
- saw tooth pattern on ECG
- 2:1 conduction
- atrial rate ~ 300bpm
features of atrial flutter on ECG
- 300bpm
- saw tooth pattern
- 2:1 conduction
treatment of atrial flutter
rate or rhythm control
like in AF
what is supraventricular tachycardia?
when abnormal electrical signals from above the ventricles cause tachycardia
narrow complex tachycardia QRS <120ms
What causes SVT?
- electrical signal re-entering atria from the ventricles
- re-entry loop
- this causes another ventricular contraction
How does SVT present on ECG?
- narrow complex tachycardia <120ms (3 small boxes)
- p wave + T wave merge
management of SVT
- continuous ECG monitoring
Step wise approach if not life threatening: - vagal manoeuvers (first line)
- rapid bolus of adenosine (first line drug)
- verapamil or B blocker
-
synchronised DC cardioversion
. - if life threatening: synchronised DC cardioversion under GA + IV adenosine if unsuccessful
Describe vagal manoeuvres
- stimulate vagus nerve > increases parasympathetic nervous system
- slowing electrical activity of heart
- e.g. valsalva manoeuvre, carotid sinus massage, diving relfex
describe valsalva manoeuvers
- involve increasing intrathoracic pressure
- pt blows hard against resistance e..g blowing into syringe for 10 seconds
describe carotid sinus massage
- massage over the carotid sinus in the neck
- stimulates baroreceptors
Describe the diving reflex
briefly submerging pt face in cold water
mechanism of action of adenosine
slows cardiac conduction through AV node
Who should adenosine be avoided in?
- asthmatics
- COPD
- heart failure
- heart block
- severe hypotension
how should adenosine be administered for SVT management
rapid IV bolus into large proximal cannula
first 6mg > 12mg > 18mg
what should you warn a patient about before giving adenosine?
it may feel like theyr’e dying or their heart has stopped
descibe synchronised DC cardioversion
- electric shock applied to heart to restore normal sinus rhythm
- shock synchronised with ventricular contractions at the R wave
why is synchronised cardioversion used in patients with a pulse?
to avoid shock during T wave
as this can cause VF > cardiac arrest
management of paroxysmal SVT
- long term meds e.g. B blockers, CCBs, amiodarone
- radiofrequency ablation
What arrhythmias can radiofrequency ablation permanently resolve?
AF
atrial flutter
SVT
WPW syndrome
Describe Wolff Parkinson White syndrome
- caused by extra electrical pathway connecting atria + ventricles (Bundle of Kent)
- pre-excitation syndrome
ECG changes in Wolff Parkinson White syndrome
- short PR interval <120ms
- wide QRS complex >120ms
- delta wave
Management of WPW syndrome
radiofrequency ablation of accessory pathway (definitive treatment)
What are Broad complex tachycardias
- tachycardia with wide QRS complex >120ms (3 small boxes)
- VT or unclear cause
- polymorphic VT e.g. torsades de pointes
- AF with BBB
- AVT with BBB
Outline prolonged QT intervals
- QT interval from start of QRS complex to end of T wave
- QTc estimates the QT interval if HR was 60
- prolonged QT >440/460ms
- represents prolonged repolarisation of myocytes
Outline Torsades de pointes
- type of polymorphic ventricular tachycardia
- broad complex tachycardia >120ms
features of torsades de pointes on ECG
- looks like VT but with appearance that QRS is twisting around baseline
- QRS height progressively gets smaller + larger + smaller again
treatment of torsades de pointes
correcting underlying cause
IV magnesium
defibrillation
What are ventricular ectopics?
premature ventricular beats caused by random electrical discharges outside the atria
Features of ventricular ectopics
- irregularly irregular pulse
- that goes back to sinus at high HR
- feeling of missing a beat or extra beat
Appearance of ventricular ectopics on ECG
isolated random abnormal broad QRS complexes
on otherwise normal ECG
what is bigeminy?
when every other beat is a ventricular ectopic
Management of ventricular ectopics
- reassurance + no treatment if otherwise F+W
- specialist advice in pts with underlying heart disease, frequent or concerning symptoms, or family history of sudden head
- beta blockers to manage symptoms
Causes of hyperkalaemia
- AKI
- metabolic acidosis
- Addison’s disease
- rhabdomyolysis
- high K+ diet
- drugs *e.g. ACEi, ARBs, spironolactone, heparin,
How does hyperkalaemia appear of ECG
- tall tented T waves
- flattned p waves
- broad QRS complex >3 small squares
- sinusoidal wave pattern
Management of hyperkalaemia
- combined insulin dextrose infusion
- calcium gluconate
- calcium resonium
- salbutamol nebs
Causes of hypokalaemia
- vomiting
- thiazide or loop diuretics
- Cushing’s syndrome + Conn’s syndrome
- diarrhoea
- magnesium deficiency
How does hypokalaemia appear on ECG?
- U waves
- small or absent T waves
- prolonged PR interval
- ST depression
If a patient is hypokalaemic + you’ve giving lots of replacement K+ but K+ is not increasing, what should you do?
check magnesium + manage appropriately
Treatment of non-shockable rhythms
- CPR 30:2
- adrenaline 1mg ASAP
- repeat adrenaline every 5 mins
Treatment of shockable rhythms
- CPR 30:2
- defibrillation
- IV adrenaline 1mg once compression have restarted after 3rd shock
- repeat adrenaline every 5 mins
- IV amiodarone 300mg after 3 shocks
- further 150mg after 5 shocks
ECG changes in LBBB
WiLLiaM
W in V1
M in V6
Causes of LBBB
- MI
- hypertension
- aortic stenosis
- cardiomyopathy
Management of LBBB
- no treatment if asymptomatic + no other heart problems
- drugs to control conditions causing LBB e.g ACEi for HTN
- pacemaker
- cardiac resynchronisation therapy
ECG features of RBBB
MaRRoW
M in V1
W in V6
Causes of RBBB
- increasing age
- RV hypertrophy
- cor pulmonale
- PE
- MI
Management of RBBB
- no treatment if asymptomatic + no other heart problems
- drugs to control conditions causing RBB e.g ACEi for HTN
- pacemaker
- cardiac resynchronisation therapy
