AKA: Accelerated Ventricular Rhythm
Accelerated Idioventricular Rhythm (AIVR) Overview
- AIVR results when the rate of an ectopic ventricular pacemaker exceeds that of the sinus node.
- Often associated with increased vagal tone and decreased sympathetic tone.
- Proposed mechanism is enhanced automaticity of ventricular pacemaker, although triggered activity may play a role especially in ischaemia and digoxin toxicity.
- AIVR is classically seen in the reperfusion phase of an acute STEMI, e.g. post thrombolysis.
- Usually a well-tolerated, benign, self-limiting arrhythmia.
- Regular rhythm.
- Rate 50-110 bpm.
- Three or more ventricular complexes.
- QRS complexes >120ms.
- Fusion and capture beats.
Isorhythmic AV dissociation
Causes of Accelerated Idioventricular Rhythm (AIVR)
There are multiple causes of AIVR including:
- Reperfusion phase of an acute myocardial infarction (= most common cause)
- Beta-sympathomimetics such as 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
- AIVR is a benign rhythm in most settings and does not usually require treatment.
- Usually self limiting and resolves when sinus rate exceeds that of the ventricular foci.
- Administration of 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 in an attempt to increase sinus rate and AV conduction.
- Ventricular rhythm at 60 bpm.
- Multiple sinus capture beats.
Competing sinus and idioventricular pacemakers are present. There is underlying sinus arrhythmia, with sinus capture occurring when the sinus rate exceeds the idioventricular rate.
This patient was a healthy 36-year old marathon runner with presumably very high resting vagal tone causing sinus bradycardia and sinus arrhythmia.
Another ECG from the same patient showing:
- AIVR at 60 bpm.
- Isorhythmic AV dissociation with frequent sinus capture beats.
- A fusion beat.
- Ventricular rhythm at 75 bpm.
- AV dissociation — a dissociated P wave is seen in the rhythm strip, another in lead aVL. Elsewhere, dissociated P waves cause intermittent deformation of the QRS complexes.
- The taller left rabbit ear sign is present — there is a notched R wave in V1 with a taller initial R wave; this is highly specific for a ventricular origin of the QRS complexes.
- Broad complex at 90 bpm.
- No visible P waves.
This dysrhythmia occurred following reperfusion from an anterior STEMI.
- Brady WJ, Truwit JD. Critical Decisions in Emergency and Acute Care Electrocardiography
- Hampton, JR. The ECG In Practice, 6e
- Surawicz B, Knilans T. Chou’s Electrocardiography in Clinical Practice: Adult and Pediatric, 6e
- Wagner, GS. Marriott’s Practical Electrocardiography 12e
- Chan, TC. ECG in Emergency Medicine and Acute Care
- Mattu, A. ECG’s for the Emergency Physician
LITFL Further Reading
- ECG BASICS — Waves, Intervals, Segments and Clinical Interpretation
- ECG A to Z by diagnosis –alphabetical diagnostic approach to the ECG
- ECG CLINICAL CASES — ECG’s placed in clinical context with a challenging Q&A approach
- 100 ECG Quiz — Self-assessment tool for examination practice
- ECG Reference SITES and BOOKS — the best of the rest
- LITFL ECG IMAGE Database — Searchable database of LITFL ECG’s
- ECG and Cardiology Eponymous Syndromes — Cheats guide to eponymous emancipation
- ECG Exam Template — a framework for answering ECG exam questions.