What are the 12-lead EKG findings for accelerated idioventricular rhythm?

This case explains the expected 12-lead EKG findings after successful STEMI treatment and reperfusion


Article Updated July 31, 2017

You were dispatched to a rural medical facility to transport a patient diagnosed with an acute coronary syndrome to the closest cath lab. Upon arrival, you are briefed on the current status of your patient, a 64-year-old diabetic, hypertensive female, who was brought to the facility an hour ago with evidence of a STEMI.

She arrived within 30 minutes of her symptoms' onset and has been treated with aspirin, heparin and thrombolytics for several minutes now. She reports that she is pain-free and actually feels much better.

As your patient calmly talks to you en route to the cath lab, you glance at the rhythm monitor casually and notice a rhythm change in the 12-lead EKG.

The EKG Club learning objectives for this care are to: 

  • Basic: Identify the origin of ectopic impulses.
  • Intermediate: Identify treatment options for disrythmias.
  • Advanced: Differential diagnosis for post STEMI patients. 

Initial patient treatment

Your partner agrees with you that this is a case of an accelerated idioventricular rhythm (AIVR), most likely resulting from the reperfusion of an injured heart muscle. You both determine that no treatment is necessary, as reperfusion is usually self-limited; however, you begin to watch the rhythm more closely. As the patient continues to be asymptomatic and maintains adequate cerebral perfusion, you see no benefit to changing the treatment.

Response to treatment and report to hospital

You contact medical command to inform them of the patient’s status. The physician agrees with your assessment and your decision to withhold any interventions.  Shortly after communicating with medical command, there is a change.

The patient spontaneously converts back to a normal sinus rhythm. Upon reassessment, the patient continues to feel the same and no other changes are noted in her condition. You deliver the patient at the receiving hospital without further incident.

Acute MI reperfusion

When treating acute STEMI with thrombolytics, there are three major signs of successful reperfusion (adapted from Dr. Mattu). These are:

  1. T wave inversion within the first four hours. If the T wave inversions occur beyond four hours, it's uncertain.
  2. Resolution of the ST elevation by at least 70 percent in the lead with maximal ST elevation.
  3. Development of a "reperfusion arrhythmia," most notably accelerated idioventricular rhythm (AIVR). 

A STEMI patient that continues to have persistent pain/symptoms OR an absence of ST elevation resolution after 90 minutes warrants strong consideration of rescue angioplasty.

Reperfusion arrhythmias may be experienced for up to three hours after reperfusion begins. These may present as premature contractions, transient tachycardia lasting only a few moments, or other abnormal rhythms.

In this 12-lead EKG case, the AIVR is easily explained by reperfusion. AIVR is an automatic, ectopic ventricular rhythm mimicking ventricular tachycardia, which generally does not affect the patient's course or condition. Morbidity and mortality depends on the underlying condition.

AIVR is a very common reperfusion disrythmia but requires no treatment. When hemodynamic compromise arises, it is usually due to the bradycardia, which could be treated with atropine 0.5mg IV or transcutaneous pacing, but these are rarely needed.
 
EKG findings of AIVR include:

  • A run of three or more premature ventricular beats above 30-40 bpm, usually around 60-100 bpm, that can last for as long as one to two minutes.
  • The QRS complex is usually wide due to the ventricular involvement, just as you would see in a premature ventricular contraction.
  • As the AIVR emerges, the P-R intervals shorten and the P-P intervals prolong until the P-waves no longer relate to the QRS complex. This reflects the ventricular control of pacing.
  • As the AIVR fades away, P-P intervals shorten and P-waves again are seen before each QRS complex. Remember, ventricular tachycardia should have a rate that exceeds 120bpm. 

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