Accelerated Idioventricular Rhythm

An accelerated idioventricular rhythm is basically a rapid idioventricular rhythm (Figure 31-6). The rates for accelerated idioventricular rhythm are above the rates typically expected for the ventricular pacemakers and are typically between 50 and 100 BPM. The rhythm is due to increased automaticity of an ectopic ventricular pacer. The ventricular complexes have the morphologic characteristics of the intrinsic ventricular rhythms (wider than 0.12 seconds, bizarre appearance, ST-segment and T-wave abnormalities).

The ECG complex for accelerated idioventricular rhythm shows a sharp dip, a curved peak, and a curved dip occurring at high frequency.

Figure 31-6 Accelerated idioventricular rhythm.

© Jones & Bartlett Learning.

Accelerated idioventricular rhythms are typically very regular, but there may be some slight irregularity at the onset of the rhythm. The rhythm can usually be overcome by overdrive pacing from an external pacer or by using pharmaceutical agents that speed up the heart or suppress ventricular activity. Overdrive pacing refers to using a pacemaker faster than the patient’s rate at the time. This will allow manual pacing to set the pacemaking rate in the hopes that when you lower the rate of the pacemaker, the patient’s own pacemaker can assume its position as the dominant pacemaker once more. Once again, be careful of pharmaceutical intervention because the ventricular pacemakers are the last defense against asystole or absence of rhythm. Overdrive pacing can be attempted as long as the patient is hemodynamically stable. But, as usual, in the case of any hemodynamic compromise, electrical cardioversion or defibrillation are still the treatments of choice.

Accelerated idioventricular rhythm may occur in the absence of any supraventricular rhythm, or it can occur as a ventricular response to an AV dissociation or block (Figure 31-7). As you can imagine, the faster ventricular rates in accelerated idioventricular rhythms can lead to more variability in fusion complexes with the dissociated P waves and, as we shall see in the next section, with partially conducted supraventricular complexes.

The ECG complex shows accelerated idioventricular rhythm with P waves buried at different points in the complexes. P-P intervals are regular.

Figure 31-7 Accelerated idioventricular rhythm with AV dissociation.

© Jones & Bartlett Learning.

Accelerated idioventricular rhythms are commonly found in patients having acute myocardial infarctions. They are also part of a set of rhythm disturbances seen commonly after reperfusion has begun during the administration of thrombolytics for an acute myocardial infarction (AMI). In this clinical setting, this set of arrhythmias is known as the reperfusion arrhythmias. The reperfusion arrhythmias are typically stable and transient in nature, although they are scary to observe on a monitor. When idioventricular or accelerated idioventricular rhythms appear as reperfusion arrhythmias, they do not require treatment unless they are causing significant hemodynamic compromise.