Accelerated idioventricular rhythm

Background

• Results when rate of an ectopic ventricular pacemaker exceeds sinus node
• Usually benign,self limiting
• Terminology
  • Idioventricular rhythm: 20-40 bpm
  • Accelerated idoventricular rhythm: 40-120 bpm
  • Ventricular tachycardia: >120 bpm

Causes

• Reperfusion phase of acute myocardial infarction (most common cause)
• Beta-sympathomimetics (isoprenaline or adrenaline)
• Drug toxicity, especially digoxin, cocaine and volatile anaesthetics such as desflurane
• Electrolyte abnormalities
• Cardiomyopathy
• congenital heart disease
• myocarditis
• Return of spontaneous circulation (ROSC) following cardiac arrest
• Athletic heart

Clinical Features

• Asymptomatic or palpitations

Differential Diagnosis

Wide-complex tachycardia

Assume any wide-complex tachycardia is ventricular tachycardia until proven otherwise (it is safer to incorrectly assume a ventricular dysrhythmia than supraventricular tachycardia with abberancy)

• Regular
  • Monomorphic ventricular tachycardia
  • PSVT with aberrant conduction:
    • PSVT with bundle branch block^
    • PSVT with accessory pathway
    • Atrial flutter with bundle branch block^
  • Sinus tachycardia with bundle branch block^
  • Accelerated idioventricular rhythm (consider if less than or ~120 bpm)
  • Metabolic
    • Hyperkalemia
    • Digoxin toxicity
    • Severe metabolic acidosis
• Irregular
  • Atrial fibrillation/atrial flutter with variable AV conduction AND bundle branch block^
  • Atrial fibrillation/atrial flutter with variable AV conduction AND accessory pathway (e.g. WPW)
  • Atrial fibrillation + hyperkalemia
  • Polymorphic ventricular tachycardia
    • Torsades de pointes
    • Nonsustained ventricular tachycardia

^Fixed or rate-related

Palpitations

• Arrhythmias:
  • Narrow-complex tachycardias
  • Wide-complex tachycardias
  • AV blocks
    • Second Degree AV Block Type I (Wenckeback)
    • Second Degree AV Block Type II
    • Third Degree AV Block
  • Premature atrial contraction
  • Premature junctional contraction
  • Premature ventricular contraction
  • Sick sinus syndrome
  • Wandering atrial pacemaker
• Non-arrhythmic cardiac causes:
  • Acute coronary syndrome
  • Cardiomyopathy
  • Congenital heart disease
  • Congestive heart failure (CHF)
  • Mitral valve prolapse
  • Pacemaker complication
  • Pericarditis
  • Myocarditis
  • Valvular disease
• Psychiatric causes:
  • Panic attack
  • Anxiety
  • Somatic Symptom Disorder
• Drugs and Medications:
  • Alcohol
  • Caffeine
  • Drugs of abuse (e.g. cocaine)
  • Medications (e.g. digoxin, theophylline)
  • Tobacco
• Misc
  • Anemia
  • Hyperthyroidism
    • Thyroid storm
  • Pulmonary embolism
  • Dehydration
  • Sepsis
  • Pheochromocytoma

Evaluation

ECG features

• Regular rhythm
• Rate 50-110 bpm
• Three or more ventricular complexes
• QRS complexes >120ms
• Fusion and capture beats

Management

• AIVR is a benign rhythm in most settings and does not usually require treatment
• Self limiting and resolves when sinus rate exceeds that of the ventricular foci
• Anti-arrhythmics may cause precipitous haemodynamic deterioration and should be avoided
• Treat the underlying cause: e.g. correct electrolytes, restore myocardial perfusion
• Patients with low-cardiac-output states (e.g. severe biventricular failure) may benefit from restoration of AV synchrony to restore atrial kick – in this case atropine may be trialled to increase sinus rate and AV conduction

Disposition

• Normally outpatient

External Links

• http://lifeinthefastlane.com/ecg-library/aivr/