Arrythmias Flashcards
What are the 5 main clinical causes of arrythmias?
I DAMAG(E)
- Inflammation (viral myocarditis
- Drugs (direct or indirect)
- Abnormal anatomy (LVH, acc. pathways)
- Metabolic (hypoxia, ischaemia, electrolyte)
- Autonomic nervous system
- Genetic (ion channel genes)
What are ectopic beats?
Beats or rhythms that originate in places outwith the SA node
What is Wolf Parkinson White syndrome?
- Accessory pathway tachycardia
What is triggered activity?
- In the terminal phase of the AP (phase 3) a small depolarisation may occur and if of sufficient magnitude can lead to a sustained train of depolarisations (TA)
- This mechanism underlies digoxin toxicity, TdP in the long QT syndrome and hypokalaemia
What what two factors can cause rentry?
- Structural abnormalities: accessory pathways, scar from myocardial infarction, congenital heart disease
- Functional: Conditions that depress conduction velocity or shorten refractory period promote functional block, e.g. ischaemia, drugs
What are the main symptoms of an arrhythmia?
- Palpitations
- Dyspnoea
- Dizziness
- Presyncope/Syncope
- Sudden cardaic death
- Angina
- Heart failure
Why would you use a 12 lead ECG when dealing with arrythmias?
- To assess rhythm
- Signs of previous MIs (Q waves) or pre-excitation (Wolf Parkinson White syndrome)
What does pre excitation look like on an ECG?
Why would you do an exercise ECG for a suspected arrhythmia?
- To assess for ischaemia
- Test for exercise induced arrhythmia
When would you use a 24hr Holter ECG when testing for arrhythmia?
- To assess for paroxysmal arrhythmia
- To like symptoms to underlying heart rhythm
Why would you use an echo with suspected arrhythmia?
To assess for structural diseases e.g.
- enlarged atria in AF
- LV dilatation
- previous MI scar, aneurysm
What is an electrophysiological study?
- Trigger the clinical arrhythmia and study its mechanism/pathway
- Opportunity to treat arrhythmia by delivering radiofrequency ablation to extra pathway
What is Normal Sinus Arrhythmia?
- Variation in heart rate, due to reflex changes in vagal tone during the respiratory cycle
- Inspiration reduces vagal tone and increases HR
- Physiological (normally seen in young, healthy people)
What is sinus bradycardia and what can cause it?
- <60 bpm
- physiological (i.e. athlete)
- drugs (ß blocker)
- ischaemia: common in inferior STEMIs
What is the treatment of sinus bradycardia?
- atropine (if acute, e.g. acute MI)
- pacing if haemodynamic compromise
What is and what causes sinus tachycardia?
- >100 bpm
- physiological (anxiety, fever, hypotension, anaemia)
- inappropriate (drugs etc.)
How do you treat sinus tachycardia?
- Treat underlying cause
- ß blockers
What are the symptoms and treatment of atrial ectopic beats?
- Asymptomatic
- Palpitations
- Generally no treatment
- ß blockers may help
- Avoid stimulants e.g. coffee/cigarettes
What are AVNRT, AVRT and EAT
- AVNRT = AV nodal reentrant tachycardia
- AVRT = AV reentrant tachcardia (via an accessory pathway)
- EAT = ectopic atrial tachycardia
What is orthodomic AVRT? What does it look like on a 12 lead ECG?
Antegrade (moving forward) conduction through AV node due to accessory pathway
What is antidromic AVRT? What does it look like on a 12 lead ECG?
Retrograde (moving backwards) conduction through AV node
What is the management of acute supraventricular tachycardia?
- Increase vagal tone (valsalva, carotid massage)
- Slow AVN conduction - IV adenosine or verapamil
What is the management of chronic supraventricular tachycardia?
- Avoid stimulants
- Electrophysiologic study and Radiofrequency ablation (first line in young, symptomatic patients
- Beta blockers
- Antiarrhythmic drugs
What is RFCA?
- Radiofrequency catheter ablation
- Selective cautery of cardiac tissue to prevent tachycardia, targeting either an automatic focus or part of a re-entry circuit
What does the Electrophysiologic Study and RFCA procedure involve?
- ECG catheters to heart via femoral veins
- Intracardiac ECG recorded during sinus rhythm, tachycardia and during pacing manouvres to locate tachycardia mechanism
- catheter placed over focus/pathway and tip heated to 55-65oC
What is heart block?
AVN conduction disease
What are some causes of heart block?
- Ageing
- Acute MI
- Myocarditis
- Infiltrative disease (amyloid)
- Drugs (ß blockers, CCBs)
- Calcific aortic valce disease
- Post-aortic valve surgery
- Genetic: Lenegre’s disease, myotonic dystrophy
What defines 1st degree heart block, what is the treatment and what is the follow up?
- PR interval longer than normal (>0.2s)
- Treatment: none
- Long term follow up reccomended as advanced block may develop over time
What is Mobitz 1 second degree heart block? What does it look like on an ECG?
Mobitz I
- progressive lengthening of the PR interval, eventually resulting in a dropped beat
- usually vagal in origin
What is 3rd degree heart block? What is the treatment of it and what does it look like on a 12 lead ECG?
- Where no APs from the SA node/atria get through the AV node
- Ventricular pacing = treatment
What is Mobitz 2 second degree heart block? What is its treatment and what does it look like on an ECG?
- Pathological, may progress to complete heart block (3rd degree HB)
- Usually 2:1, or 3:1, but may be variable
- Permanent pacemaker indicated
What are the types of pacemakers?
- Single chamber (paces the RA or RV only)
- Dual chamber (paces both RA and RV) - maintains AV syncrony (preseves atrial kick), used for AVN disease
What are some causes of ventricular ectopics?
- Structural causes: LVH, heart failure, myocarditis
- Metabolic: Ischaemic heart disease, electrolytes
- May be a marker for inherited cardaic conditions
When do you need to further investigate ventricular ectopics and what can be done to treat it?
- Further investigation if worse on exercise
- ß blockers
- Ablation of focus
What is the danger of ventricular tachycardia and what are the causes
- Can cause sudden death
- Most patients have CAD/a precious MI
- More rare: cardiomyopathy or inherited syndromes such as Long QT or Brugada
What are the defining ECG characteristics of VT?
- Rapid, wide, distorted QRS
- Large, inverted T waves
- Usually no P waves
What is ventricular fibrilation overall?
- Chaotic ventricular electrical activity which causes the heart to lose the ability to function as a pump
What is the long term treatment
- Correct ischaemia e.g. revascularisation
- Optimise congestive heart failure therapies
- ICD
- VT catheter ablation
What should you treat a wide QRS tachycardia with a history of CAD/HF as?
VT until proven otherwise
What use are AADs in VTs
Reduce symptoms - ineffective on survival
What is Atrial Fibrilation?
- Chaotic and disorganized atrial activity
- Causes a irregular heartbeat
- Most common sustained arrythmia
- Incidence increases with age
What are the three types of atrial fibrilation?
- Paroxysmal - lasting <48 hrs, often recurrent
- Persistent - Episode >48 hrs that can be cardioverted to NSR, unlikely to spontaneously revert to NSR
- Permanent - no way to restore NSR
What are the methods of termination of atrial fibrilation?
- Pharmacologic cardioversion with AADs (30% effective)
- Electrical cardioversion (90% effective)
- Spontaneous reversion to sinus rhythm
What is lone A Fib?
- A Fib with absence of any heart disease and no evidence of ventricular dysfunction
- Could be gnetic
- Significant stroke rate if >75 yo
What are the symptoms of A Fib?
- Palpitations
- Pre-syncope (dizziness), Syncope
- Chest pain
- Dyspnoea
- Sweatiness
- Fatigue
What is the atrial rate, rhythm, ventricular rate and signs of A Fib on an ECG?
- Atrial: >300bpm
- Rhythm: Irregularly irregular
- Ventricular rate: variable
- Signs: no P waves, presence of F
What complication can be caused by A Fib?
- Reduced diastole, reduced CO
- Can lead to congestive heart failure, especially if diastolic dysfunction
What is a dangerous ventricular rate in A Fib?
- <60 bpm points to AV conduction disease
- Caution w AADs
- May require permanent pacing
What are the main aims of atrial fibrilation management?
- Rhythm control - attempt to maintain SR
OR
- Rate control - accept AF but control V rate
- Anticoagulation for both if approaches high risk for thromboembolism
What four drugs can be used to slow down AVN conduction and treat rate control of A Fib?
- Digoxin
- Betablockers
- Verapamil, diltiazem
- Alone or in combination
What can be dine to restore and maintain NSR in A Fib?
Restore
- Pharmacological (AAM e.g. amiodarone)
Maintain
- AAMs
- Catheter ablation of atrial focus / pulmonary veins
- Surgery (Maze procedure)
What is TdP?
Torsades de Pointes
- Heart rate: 200 - 250 bpm
- Rhythm: Irregular
- Recognition:
- Long QT interval
- Wide QRS
- Continuously changing QRS morphology
What score can be used to identify likelhood of a stroke?
CHA2DS2-VASC
If you have A Fib and mitral valve disease what should be done?
Anticoagulation
What is A Flutter, where does it originate and what can it lead to?
- Rapid and regular form of A tachycardia
- Usually paroxysmal
- Sustained by macro-reentrant circuit in RA
- Can lead to A Fib or result in thrombo embolism
What is the defining characteristic of a A Flutter ECG?
Sawtooth baseline
What are the A Flutter treatment options?
- RF ablation (80-90% long term success
- AAM - slow ventricular rate, restore and maintain NSR
- Cardioversion
- Warfarin to prevent thromboembolism
What are shockable and unshockable rhythms?
- Shockable
- VF
- Pulseless VT
- Non-shockable
- PEA
- Asystole
