Arrhythmias Flashcards
What is an arrhythmia?
Any deviation from the heart’s sinus rhythm
List the main types of supra-ventricular arrhythmias?
- Supraventricular tachycardia:
Atrial fibrillation
Atrial flutter
Ectopic atrial tachycardia
- Bradycardia
Sinus bradycardia
Sinus pauses
List the main types of ventricular arrhythmias
- PVC (premature ventricular complexes)
- Ventricular tachycardia
- Ventricular fibrillation
- Asystole
List the main types of Atrio ventricular node arrhythmias.
- AVNRT ( AVN Re-entry tachycardia)
- AVRT (AV reciprocating tachycardia)
- AV block (1st, 2nd and 3rd block)
What are the main causes of arrhythmias?
- Abnormal anatomy:
Left ventricular hypertrophy
accessory pathways
congenital HD
- Autonomic nervous system (ANS)
sympathetic stimulation: stress, exercise, hyperthyroidism
increased Vagal tone causing bradycardia
- Metabolic:
Hypoxia: Chronic Pulmonary disease, PE
Ischaemic myocardium: acute MI, angina
Electrolyte imbalance: K+, Ca 2+ , Mg 2+
- Inflammation: viral myocarditis
- Drugs:direct electrophysiologic effects or via ANS e.g. beta blockers
- Genetic: mutations of genes encoding cardiac ion channels e.g. the congenital long QT syndrome
What is an ectopic beat?
Beat or rhythms that originate in places other than the SA node
caused by altered automaticity (ischaemia)
or triggered activity (digoxin toxicity, Long QT syndrome)
What is the pathophysiology of a re-entry arrhythmia?
requires more than one conduction pathway, with different speed of conduction (depolarization) and recovery of excitability (refractoriness)
caused by accessory pathway tachycardia (wolf parkinson white syndrome)
where is the origin of a supraventricular arrhythmias?
above the ventricle
ie SA, atria, AV, HIS
where is the origin of a ventricular arrhythmia?
Ventricle
Discuss how a tachycardia forms.
- Ectopic focus may cause single beats or a sustained run of beats, that if faster than sinus rhythm it will take over the intrinsic rhythm
- Re-entry: triggered by an ectopic beat, resulting in a self perpetuating circuit.
Give causes of those which increase Phase 4 slope in myocyte graph causing increase in ectopics (heart rate)?
Hyperthermia
Hypoxia
Hypercapnia
Cardiac dilation
Hypokalaemia, prolongs repolarization
Give causes which decrease phase 4 slope in myocyte causing decrease in heart rate (bradycardia, heart block).
Hypothermia
hyperkalaemia
What is afterdepolarisation?
ii. what does this cause?
When a small depolarisation will occur in Phase 3 (terminal phase) of cardiac myocyte graph
ii. May cause triggered activity if it reaches threshold and lead to a sustained train of depolarisation
e. g.caused by digoxin toxicity
What are the general signs and symptoms of arrhythmias?
- Palpitations
- Chest pain
- Dysopnea
- Syncope (LOC)
- Presyncope (faintness)
- Hypotension
- Dizziness
can sometimes be asymptomatic
How would you diagnose an arrhythmia?
- 12 lead ECG (in tachycardia , during SR)
- CXR
- Echocardiogram - assess for structural heart disease
4.Stress ECG
Look for myocardial ischaemia, exercise related arrhythmias
5.24 hour ECG Holter monitoring
Event recorder: (capture the arrhythmia)
- Electrophysiological (EP) study
Induce clinical arrhythmia to study mechanism and map arrhythmia
can treat it by delivering radiofrequency ablation to extra pathway
Discuss the characteristics of Normal sinus arrhythmia.
Variation in heart rate due to reflex changes in vagal tone during the resp cycle
Inspiration reduces vagal tone and increases heart rate
What is the definition of sinus bradycardia?
Defined as heart rate <60bpm
What are the causes of Sinus bradycardia?
- Physiological: Athletes lower hearbeat
- Cardiac: Ischaemia, iatrogenic, aortic valve disease,myocarditis, Post MI and cardiomyopathy
- Drug induced: Beta blockers, amiodarone, verapamil and digoxin
- Non-cardiac: Vasovagal (verycommon) endocrine (hyperthyroidism),Metabolic (hypoxia, hyperkalaemia)
How do you manage sinus bradycardia?
- Address the cause
- Give atropine if adverse effects and acute
- If atropine not sufficient then transcutaneous pacing or haemodynamic compromised (Hypotension, CHF)
What is sinus tachycardia?
When heart rate is greater than 100 bpm
What are the main causes of sinus tachycardia?
- Physiological: exercise, anxiety, hypotension, pain
- Bleed
- dehydration
- Drugs (caffeine, nicotine and salbutamol)
- Anaemia, sepsis , Co2 retention
- Hyperthyroidism, PE
How do you manage Sinus tachycardia?
Treat underlying cause
Beta blockers
What are the main symptoms of atrial ectopic beats?
- Palpitations
2. asymptomatic
How do you manage Atrial ectopic beats?
- Beta blockers may help
2. Avoid causes (caffeine, cigarettes)
What is the difference between AVRT and AVNRT?
AVRT - circuit using the AVN and AP’way (macro-reentry
AVRNT - circuit within the AVN (micro-reentry)
What is antidromic AVRT?
Retrograde (anticlockwise )conduction through AVN
properties:
- Wide QRS complex with delta wave
- P wave rarely seen
- if P-wave visible retrograde and occurs just before QRS
What is orthodromic AVRT?
Antegrade (clockwise) conduction through AVN
Properties:
- Normal QRS duration
- No delta wave
- Retrograde P wave after QRS
How do you manage supraventricular tachycardias?
Acute management:
Increase vagal tone: valsalva manoeuvre or carotid massage.
- Slow conduction in the AVN
carotid massage only used for young patients and with a low risk of stroke
IV Adenosine - not if asthmatic
IV Verapamil
Chronic management: Avoid stimulants Electrophysiologic study and Radiofrequency ablation (first line in young, symptomatic patients) Beta blockers Antiarrhythmic drugs
What is an RFCA?
Radiofrequency catheter ablation
prevents tachycardias by attacking automatic focus or part of re entry circuit
What is heart block?
Disrupted passage of electrical impulse through the AV node
What is 1st degree heart block?
ii. How do you diagnose it?
iii. How do you manage it?
Conduction between atria and ventricles are delayed
ii. PR interval is prolonged (>0.2 s) and unchanging; no missed beats
iii. No treatment - should have long term follow up as more advance block may occur
What is 2nd degree heart block
ii. what are the two types?
Intermittent block at the AVN (dropped beats)
ii. Mobitz I and Mobitz II
What occurs in 2nd degree heart block Mobitz I?
PR interval is longer and longer until a QRS is missed, the pattern then resets- wenckebach phenomen
causes missed beat
usually vagal in origin
What occurs in 2nd degree heart block mobitz II?
Is when there is a fixed number of non conducted P waves for the number of QRS complexes.
PR interval is constant but there will be P waves without QRS.
Usually 2:1 or 3:1.
ECG: progressive lengthening of PR and then missed beat.
May deteriorate into complete heart block or asystole.
How do you manage Mobitz II?
Ventricular pacemaker
What is 3rd degree Heart block?
complete heart block - no impulses from atria and ventricles
P waves and QRS waves appear independent of each other
patient may become very bradycardic - may be Haemodynamicaly uncompromised
How do you manage 3rd degree heartblock?
Ventricular pacing
What are the causes of Heart block?
- IHD (especially inferior MI
- acute myocarditis
- Sick sinus syndrome
- Drugs: Digoxin toxicity B blockers and CBBs
- Age
- Calcification aortic valve disease
- Post- aortic valve surgery
- Genetic: Lenegre’s disease and myotonic dystrophy
What are the two main types of pacemakers?
single chamber - right atria or right ventricle only
dual chamber - (paces the RA and RV)
Maintains A-V synchrony (preserves atrial kick)
Used for AVN disease
What are ventricular ectopics?
Ventricular ectopic are extra electrical impulses that arise from the ventricles.
The may occur healthy individuals but are also the most common post MI arrhythmia and indicate myocardial instability.
What are the main causes of ventricular ectopics?
- Structural causes: LVH, heart failure, myocarditis
- Metabolic: Ischaemic heart disease, electrolytes
- May be marker for inherited cardiac conditions
- If worse on exercise, need to investigate further
- Beta-blockers, Ablation of focus
What is ventricular tachycardia?
Type of broad complex tachycardia where ECG shows rate >100 bpm and QRS complexes >120ms
What are the causes of Ventricular tachycardia?
Coronary artery disease
A previous myocardial infarction
Rare causes:
- Cardiomyopathy
Inherited/ Familial arrhythmia syndromes
Long QT, Brugada syndrome
How do you diagnose VT?
ECG:
- The T waves are large with deflections opposite the QRS complexes.
- The ventricular rhythm is usually regular.
- P waves are usually not visible.
- The PR interval is not measurable.
- A-V dissociation may be present.
- V-A conduction may or may not be present.
How do you differentiate VT from SVT?
Difficult on ECG surface however several factors can help point to VT:
- +ve or -VE QRS concordance in all chest leads (i.e all +VE in R wave and all negative in QS)
- QRS >160ms
- Fusion or capture beats
- marked left deviation