Arrhythmias Flashcards
Atrial fibrillation Atrial Flutter WPW Brugada Heart block SVT Ventricular tachycardia Ventricular fibrillation Prolonged QT
what is atrial fibrillation?
chaotic irregular atrial rhythm
AVN responds intermittently so there is irregular ventricular rate
What does AF increase the risk of?
embolic strokes
What are the causes of AF?
- HF/ischaemia
- HTN
- MI
- PE
- mitral valve disease
- Pneumonia
- Hyperthyroidism
What are the sx of AF
Palpitations, SOB, chest pain, faintness, asymptomatic
What is the one main sign of AF
irregularly irregular pulse
What can be found on ECG in AF
absent p waves
irregular QRS complexes
What are the 3 main types of AF?
- paroxysmal - 2 or more episodes that self-terminate (<7 days)
- persistent - episodes that don’t self-terminate (>7 days)
- permanent - continuous AF that can’t be cardioverted (chronic)
Give the management of acute AF
- O2, U+E, emergency cardioversion
- Rx associated illness e.g. MI
- Control ventricular rate: diltiazem, verapamil, metoprolol
- start full anticoagulation w LMWH
What are the two main options for treatment of AF
- RATE control - BB or CCB (diltiazem)+ digoxin if needed
2. Rhythm control - cardio version, get the pt into and maintain normal sinus rhythm
When can a patient not be cardioverted and why?
if they have had sx for more than 48hrs or aren’t on anticoagulants as the moment a pt switches from AF to sinus rhythm is the highest risk of embolism
What is the management of AF w onset under 48hrs
Heparinise
Those w RF s for ischaemic stroke - lifelong anticoagulation
Cardioversion
What are the types of cardio version? when are they used?
- electrical cardioversion ‘DC’
2. pharmacological - amiodarone if structural HD (most elderly ppl), flecainide if not
What is the management of AF >48rs
Anticoagulation for at least 3 weeks prior to cardio version
Electrical cv recommended
Anticoagulate for 4 weeks
What is atrial flutter
form of SVT where there is succession of rapid atrial depolarisation waves
How does atrial flutter appear on ECG?
Sawtooth pattern
What is the treatment of atrial flutter?
similar to AF but is more sensitive to electrical CV and requires lower energy levels
Cure is radio frequency ablation of tricuspid valve isthmus
What is 1st degree HB
PR interval is >0.2s
always generates a QRS
What are the sx and rx of 1st degree HB
usually asymptomatic, no Rx needed
What are the different types of 2nd degree heart block?§
1st (wenkebach) - progressive prolongation of PR interval until QRS is dropped
2nd PR interval constant but P wave often not followed by QRS complex
What is 3rd degree hb?
complete HB, no association between p waves and QRS c
What is the management of 2nd and 3rd degree heart blocks?
type 1 - none unless symptomatic, atropine IV or temp pacemaker
type 2 - permanent pacemaker
3rd degree - permanent pacemaker unless cause is reversible
What is Wolff Parkinson white?
congenital accessory conducting pathway (bundle of Kent) between atria and ventricles causing atrioventricular re-entry tachycardia (paroxysmal SVT)
Why is WPW dangerous?
episodes of AF or an abnormal heart rhythm can degenerate to VF as the accessory pathway doesn’t have the rate slowing properties of the AV node
What are the symptoms in WPW
palpitations, SOB, lightheadedness and syncope
What findings can be found on ECG in WPW?
In normal sinus rhythm: short PR interval Wide QRS Delta waves - slurred upstroke of QRS Right axis deviation (if L sided accessory pathway) During a re-entry tachycardia: no p waves tachycardia Often indistinguishable from other forms of SVT
What is the treatment for:
I) stable WPW
ii) unstable WPW
Stable: Procainamide if wide QRS Adenosine or CCB if narrow QRS Unstable: Electrical CV Long term definitive therapy: radio frequency catheter ablation
What is the inheritance pattern of Brugada syndrome?
autosomal dominant
mutation of SCN5A gene - encodes myocardial sodium ion channel protein
In what group of people is Brugada syndrome more common?
asian
Why is brugada syndrome dangerous?
can cause fainting or sudden cardiac death due to serious abnormal heart rhythms e.g. VF or polymorphic ventricular tachycardia
What ECG changes can be seen in Brugada syndrome
Convex ST segment elevation >2mm in >1 of V1-3 followed by negative T wave
Partial RBBB appearance
what is the treatment of Brugada syndrome?
implantable cardioverter defibrillator
What can cause 3rd degree heart block?
Coronary ischaemia - most common: - Inferior wall MI - damage resolves - Anterior wall mI - extensive permanent damage Hyperkalaemia Congenital - lupus
How does atropine work?
reduces vagal stimulation through the AV node
What is supraventricular tachycardia?
sudden onset of narrow complex tachycardia
How is SVT different to ST?
SVT: begins abruptly HR: 160-240 Terminated by vagal manoeuvre ST: Begins more slowly Rate <160 Not terminated by vagal manoeuvre
What is the management of paroxysmal SVT?
Acute: vagal manoeuvres e.g. valsalva, carotid sinus massage (differentiates between tachy of ventricular origin)
IV adenosine: 6mg ->12mg
Electrical CV
How are episodes of PSVT prevented?
beta blockers
radio frequency ablation
What is an alternative for adenosine?
verapamil
When is carotid sinus massage CI and why?
in elderly due to risk of stroke in those w atherosclerotic plaques in carotid arteries
how do vagal manoeuvres work?
increase the resistance of the AV node to transmit impulses through the activation of the parasympathetic nervous system conducted to the heart by th vagus nerve
How does adenosine work?
increases atrioventricular (AV) node refractoriness
What SVTs does adenosine not work and why?
atrial flutter and AF as they don’t involve the AV node
In who should adenosine not be given to and why?
Those who will not tolerate its transient bradycardic effects e.g. hypotension, coronary ischaemia, decompensated HF
asthma or COPD due to bronchospasm
What can cause ectopic beats?
post MI or normal healthy adults
When are those with ectopic beats at risk of VF?
if no gap before T wave
What is the treatment of ectopics?
iv amiodarone or just observe
Why is VT dangerous?
can turn into VF
What can be seen on ECG in VT?
Broad QRS
No p waves
T waves difficult to identify
Regular QRS w rate ~200bpm
what can cause VT
Commonly: Coronary heart disease heart failure cardiomyopathy valvular disease Less commonly: Brugada long QT prinzmetals angina sarcoidosis
What are the two main types of VT
monomorphic - commonly due to MI
Polymorphic - e.g. torsades de pointer caused by prolonged QT interval
What is the treatment of VT
If haemodynamically unstable (adverse signs SBP<90, chest pain, HF): immediate cardioversion
If stable:
amiodarone (central line ideally) IV w dextrose or lidocaine or procainamide
if drugs fail, electrical CV
What drug should not be used in VT and why?
verapamil as can precipitate cardiac arrest
When should lidocaine be used with caution in vt?
in those w severe LV impairment
How can further VTs be prevented?
surgical isoplation of arrhythmogenic area or implantable cardioverter defibrillator (indicated if severe lv function)
What is the treatment of VF?
asynchronised DC shock
What is a capture beat?
when the SA node captures ventricles in midst of AV dissociation to produce a normal QRS complex
What is a fusion beat
supra ventricular + ventricular pulse coincide to produce hybrid complex
What are the congenital causes of prolonged QT
Jervell-Lange-Nielsen syndrome (inc deafness)
Romano-Ward syndrome
What drugs cause long QT syndrome
Class 1a anti-arrhythmic drugs e.g. amiodarone, sotalol TCAs, SSRIs Methadone Chloroquine Erythromycin Haloperidol Ondansetron
What are other causes of long QT syndrome
Electrolyte imbalances: - hypocalcaemia - hypokalaemia - hypomagnesaemia Acute MI Myocarditis Hypothermia SAH
What is the management of long QT syndrome?
avoid precipitants
beta blocker
implantable cardioverter defibrillator
When does bradycardia require treatment?
- signs of haemodynamic compromise:
- shock - hypotension, pallor, cold extremities, clammy, confusion, impaired consciousness
- syncope
- Myocardial ischaemia
- HF - Risk of asystole
what is the treatment for bradycardia peri-arrest
atropine 500mcg IV (max 300mg)
transcutaneous pacing
isoprenaline/adrenaline titrated IV
What are risk factors for asystole in Bradycardia
- complete HB w broad complex QRS
- Recent asystole
- Mobitz type II AV block
- Ventricular pause >3 seconds
What is the treatment of torsades de pointes?
IV magnesium sulphate
What is the normal QTC n men and women ?
<430 in males
<450 in females
In long QT syndrome, when are implantable cardiodefibrillators required as treatment?
QTc >500 or prev cardiac arrest
