Idioventricular Rhythms

Idioventricular rhythms are rhythms where the initiating pacemaker is ectopically located in the ventricles themselves instead of the SA node or AV node. ECTOPY is an abnormal beginning point--a site of ectopic origination--of an electrical impulse within the cardiac muscle.

These ventricular arrhythmias range from asymptomatic premature ventricular beats to ventricular fibrillation. Patients at risk are those with heart failure and cardiomyopathy. There are 2 main categories of ventricular arrhythmias:

1. Lethal arrhythmias: 
   
   --Sustained ventricular tachycardia.
   --Ventricular fibrillation.

2. Nonsustained/tolerated arrhythmias:
   
   --Ventricular premature beats (VPBs)
   --Nonsustained ventricular tachycardia (NSVT)
   --Accelerated idioventricular rhythm (AIVR).

Ventricular Premature Beats (VPBs)

VPBs occur in up to 95% of those with heart failure. In those with MI, however, they signify an increased risk of death. (In non-ischemic cardiomyopathy they are not.) Because of this risk, they should be suppressed with medication.

Symptoms of VPBs: Palpitations. Beta-blockers can usually control their frequency.

Nonsustained Ventricular Tachycardia (NSVT)

NSVT "runs" (3 or more consecutive ventricular beats within a heart rate of 100-140 beats/min) occur in up to 80% of those with heart failure and cardiomyopathy.

• The rate of an idioventricular rhythm is usually 20-40 beats per minute.
• An accelerated idioventricular rate is higher, > 40 beats/minute.

ECG

These rhythms show no relationship between the QRS complexes and the preceding atrial cardiac activity.

• P waves are often absent or abnormal and
• QRS complexes are wide.

At least three consecutive beats are required to make a rhythm or “run.”