Cardiology (Arrhythmia con.) Flashcards
Wolff-Parkinson-White (WPW) syndrome is
a congenital disorder characterised by an accessory pathway that allows the conduction of electrical impulses from the atria to the ventricles directly, bypassing the atrioventricular (AV) node.
This leads to AV re-entry tachycardia (AVRT) and can cause paroxysmal supraventricular tachycardia.
This can also trigger ventricular fibrillation and cause sudden cardiac death.
WPW syndrome is associated with:
- Ebstein’s anomaly
- Hypertrophic obstructive cardiomyopathy
- Hyperthyroidism
- PRAKAG2 – this is a gene associated with a familial form of WPW syndrome
WFW ECG findings
- PR interval is short
- QRS complexes are wide with a slurred upstroke known as a delta wave
- Associated left axis deviation or right axis deviation
- Non-specific ST changes
management of WPW
The definitive management step involves radiofrequency ablation of the accessory pathway.
Initial management steps of an acute episode are similar to supraventricular tachycardia such as vagal manoeuvres except adenosine is not used if co-existing atrial fibrillation is suspected:
This is because adenosine blocks the AV node which can increase the ventricular rate potentially leading to ventricular fibrillation.
Ventricular tachycardia (VT)
is a broad complex tachycardia that originates from a ventricular ectopic focus. It is defined as 3 or more consecutive beats at a rate of >100 bpm. It requires urgent treatment as it can lead to ventricular fibrillation and cardiac arrest.
types of VT
Monomorphic VT:
* Stable SQRS morphology with no variation between beats
* Most commonly caused by myocardial infarction
Polymorphic VT:
* QRS morphology changes with each beat
* A subtype of polymorphic VT is torsades de pointes.
Presentation of VT
- Palpitations
- Breathlessness
- Chest pain or tightness
- Anxiety
- Dizziness
- Syncope
- Fatigue
- Haemodynamic instability
ECG findings VT
- Rate >100 bpm
- Wide QRS complexes (>120 ms)
- Atrioventricular dissociation
management of VT
Haemodynamically unstable
- Manage as per the Resuscitation Council UK Tachycardia guidelines. These are discussed in Adult Tachycardia.
Haemodynamically stable
- IV amiodarone through a central line
- Other options include lidocaine and implantable cardioverter-defibrillators
Torsades de Pointes
translates to “twisting of the points”. It is a polymorphic ventricular tachycardia. It is polymorphic because the QRS amplitude varies and the QRS complexes look like they are twisting around the baseline.
Torsades de pointes is associated with a prolonged QT interval and may degenerate into sustained ventricular tachycardia or ventricular fibrillation. Torsades de pointes is a life-threatening arrhythmia that may present as cardiac arrest in people with structurally intact hearts.
risk factors for torsades de pointes
1) Congenital QT syndromes (described in Long QT Syndrome)
2) Acquired QT syndromes (described in Long QT Syndrome):
- Myocardial infarction
- Drugs e.g. erythomycin
- Electrolyte imbalances
- CNS lesions e.g. subarachnoid haemorrhages
presentation of Torsades de pointes
Patients may be asymptomatic or have recurrent episodes of symptoms which are usually triggered by stress, fear, or physical exertion. Some recurring features may be:
1) Palpitations
2) Dizziness
3) Syncope:
* Preceded by: palpitations, shortness of breath, and dyspnoea
* During: pallor and cyanosis
* After: recovery period brief and there is flushing
4) Sudden cardiac death
5) Features of a congenital disorder e.g. sensorineural hearing loss in Jervell and Lange-Nielsen syndrome
ECG for Torsades de pointes
- Shows polymorphic ventricular tachycardia consistent with Torsades de pointes
- May show QT prolongation
management of Torsades de Pointes
- 1st line: IV magnesium sulfate
- Also withdraw offending drugs and correct electrolyte abnormalities
- Management of long QT syndrome
- In recurrent torsades de pointes, temporary or permanent pacing may be indicated
management of bradycardia if evidence of life-threatening signs e.g. shock, syncope, MI, HF
Give IV atropine 500 micrograms
management of adult tachycardia with life threatening features e.g. shock, syncome, MI, HF
- Give up to 3 synchronised DC shocks
Give sedation or anaesthesia if conscious
If unsuccessful:
* Amiodarone 300mg IV over 10-20 minutes
* Repeat synchronised DC shock
shockable rhythms
VF and VT
non-shockable rhythms
- pulseless electrical activity
- asystole
initial management of all patients who are unrepsonsive and not breathing properly
- Call the resuscitation team/ambulance
- Commence CPR at a ratio of 30 compressions:2 breaths (30:2)
- Attach the defibrillator/monitor and assess rhythm
- Obtain IV access
- If this isn’t possible, deliver drugs through the intraosseous (IO) route
4 Hs
- Hypoxia
- Hypovolaemia
- Hypokalaemia, hyperkalaemia, hypoglycaemia, hypocalcaemia and other metabolic disorders
- Hypothermia
4 Ts
- Thrombosis – coronary or pulmonary
- Tension pneumothorax
- Tamponade (cardiac)
- Toxins
management of shockable rhythm
If “witnessed” cardiac arrest i.e. in a coronary care unit: 3 stacked shocks then 2 minutes CPR then check rhythm then give single shocks instead and repeat
If not witnessed: 1 single shock then 2 minutes CPR then check rhythm then repeat
After third shock:
* adrenaline 1mg and amiodarone 300mg
* Repeat adrenaline 1mg every 3-5 minutes i.e. during alternate cycles of CPR
After fifth shock: further 150mg dose of amiodarone
Use lidocaine if amiodarone is not available
If non-shockable (asystole/PEA)
Adrenaline 1mg as soon as possible followed by CPR then check rhythm
Repeat adrenaline 1mg every 3-5 minutes i.e. during alternate cycles of CPRIf non-shockable (asystole/PEA)
