ARRHYTHMIAS

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ARRHYTHMIAS

• Jamil Mayet

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Arrhythmias - learning objectives

• Mechanisms of action of antiarrhythmic drugs
• Diagnosis
• To differentiate the different types of SVTs on
  the ECG
• To diagnose ventricular tachyarrhythmias from the
  ECG
• To differentiate different bradyarrhythmias from
  the ECG
• Treatment
• Understand different options drugs versus
  ablation pacing
• Importance of anticoagulation in atrial
  fibrillation
• Appreciate increasing use of ICDs

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Tachyarrhythmias

• Antiarrhythmic drugs
• Vaughn-Williams Classification
• Drugs divided according to EP effects on cells
• All are negatively inotropic
• Can also be pro-arrhythmic

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Tachyarrhythmias

• Class I
• Impede Na transport across cell membrane
• Ia increase AP duration eg quinidine,
  disopyramide, procainamide
• Ib shorten AP duration eg lignocaine, mexilitene,
  propafenone
• Ic little effect on AP eg flecainide

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Tachyarrhythmias

• Class II
• Interfere with effects of SNS on the heart eg
  beta blockers
• Class III
• Prolong AP duration but do not effect initial Na
  dependent phase eg sotalol, amiodarone
• Class IV
• Antagonise Ca transport across cell membrane
• SA and AV node particularly susceptible eg
  verapamil, diltiazem

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Supraventricular arrhythmias

• Atrial fibrillation
• Rapid atrial discharge (350-600/min)
• AV node cannot conduct all impulses
• Cardioversion (electrical or drugs) can restore
  SR
• Class Ia, Ic, III drugs may maintain SR
• Px often rate control and stroke prevention
• Rate control with digoxin, class II, III, IV
  drugs
• Anticoagulation with warfarin in most cases
• Causes include ht, ischaemia, rheumatic hd,
  alcohol, thyrotoxicosis, cardiomyopathy, PTE,
  thoracotomy, idiopathic (lone)

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Atrial fibrillation
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Supraventricular arrhythmias

• Atrial flutter
• Rapid atrial discharge (250-350/min)
• Occasional 11 conduction
• More often 21, 31, 41 conduction
• Diagnosis aided by increasing block eg CSM,
  adenosine
• Cardioversion (electrical or drugs) can restore
  SR
• Class Ia, Ic, III drugs may maintain SR
• Rate control with digoxin, class II, III, IV
  drugs
• ?Anticoagulation
• Similar causes to atrial fibrillation

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Atrial flutter
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Atrial flutter with 21 block
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Supraventricular arrhythmias

• Atrial tachycardia
• Atrial discharge slower (120-250/min)
• Occasional 11 AV node conduction
• More usually 21 conduction
• With AV block often due to digitoxicity
• Cardioversion (electrical or drug) can restore SR
• Overdrive pacing is an alternative

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Atrial tachycardia
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Supraventricular arrhythmias

• AV nodal re-entry tachycardia
• Re-entry circuit within AV node
• Rate usually 130-250/min
• CSM or adenosine may terminate arrhythmia
• Alternatives include cardioversion (electrical or
  drug) and overdrive pacing
• Prophylaxis with class II, IV, III, Ia, Ic drugs

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AV nodal re-entry tachycardia
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Supraventricular arrhythmias

• Pre-excitation syndromes
• WPW syndrome due to accessory pathway (bundle of
  Kent)
• 0.15 of population
• Accessory pathway allows rapid conduction
• Resting ECG shows short PR and delta wave
• May cause AV re-entry tachycardia
• A fib may be dangerous due to rapid conduction

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Supraventricular arrhythmias

• Pre-excitation syndromes
• Digoxin/verapamil may increase conduction in
  bundle of Kent and should be avoided
• Class Ia, Ic and III drugs slow ventricular rate
  and may cardiovert to SR
• Electrical cardioversion especially in fast A fib
• Lown-Ganong-Levine syndrome connection between
  atria and His bundle short PR no delta wave

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WPW syndrome
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Ventricular arrhythmias

• Ventricular tachycardia
• Broad complex tachycardia
• Independent atrial activity
• Capture/fusion beats
• Risk of degeneration to ventricular fibrillation
• Cardioversion (electrical or drug) can restore SR
• Overdrive pacing is an alternative
• Idioventricular tachycardia ratelt120/min often
  related to reperfusion in AMI Px often
  unnecessary

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Ventricular tachycardia
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Ventricular tachycardia
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Ventricular arrhythmias

• Torsades de pointes
• Twisting pattern
• Precipitated by prolonged QT
• May be congenital, metabolic or drug induced
• Ventricular fibrillation
• Death
• Electrical cardioversion

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Torsades de Pointes
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Rhythm Strip During Episode of Sudden Death
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VT versus SVT with aberrant conduction

• History of IHD (VT)
• Agegt60 (VT)
• Independent P wave activity (VT)
• Very broad QRS (gt140ms) (VT)
• Resting BBB of same morphology (SVT)
• Concordant QRS direction (V1-V6) (VT)
• If in doubt assume VT

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EP studies and ablation therapy

• Diagnosis and curative treatment of AVNRT, AVRT
  (eg WPW) atrial tachy and atrial flutter
• Potential curative treatment of VT
• Stratification of risk in patients with VT
• Guide need for implantable defibrillator
  insertion
• Guide antiarrhythmic drug treatment
• Potential for treatment of A fib

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Implanatable defibrillators
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Implanatable defibrillator in-situ
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Bradyarrhythmias

• Sinus node disease
• Bradycardias usually caused by idiopathic
  fibrosis, ischaemia or drugs
• Tachy-brady syndrome
• Combination of tachycardic and bradycardic
  episodes

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Sinus node disease
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Bradyarrhythmias

• AV node disease
• 1st degree prolonged PR interval
• 2nd degree Mobitz type I (Wenckebach)
  increasing PR interval then non-conducted P wave
• 2nd degree Mobitz type II non-conducted P waves
• 2nd degree 21 or 31 AV node block
• 3rd degree complete heart block
• AV block usually caused by idiopathic fibrosis
  other causes include MI, drugs and congenital
  block

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AV node disease
1st degree heart block
2nd degree heart block (21)
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AV node disease
Complete (3rd degree) heart block
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Bradyarrhythmias

• Treatment of symptomatic bradyarrhythmias often
  consists of pacing
• In the short-term drugs may be used to augment
  conduction eg atropine, isoprenaline