Causes of Idioventricular Rhythm
Idioventricular rhythm occurs most commonly in the setting of acute myocardial infarction, particularly during reperfusion, and is also seen in digitalis toxicity, structural heart disease, and occasionally in individuals without any cardiac pathology.
Primary Causes
Acute Myocardial Infarction (Most Common)
- Accelerated idioventricular rhythm is a common arrhythmia in patients with acute MI, including those with ST-segment elevation MI undergoing primary PCI 1
- The arrhythmia is more closely related to the extent of infarction than to reperfusion itself 1
- When occurring after thrombolysis during acute MI, it serves as a marker of successful reperfusion 2
- More frequent in patients with inferior infarction 3
Structural Heart Disease
- Can occur in any form of structural heart disease 2
- Associated with rheumatic heart disease, primary myocardial disease, and hypertensive heart disease 4
- Seen in patients with cardiomyopathies 2
- May occur in valvular heart disease 4
Medication-Related Causes
- Digitalis excess is a well-recognized cause 4
- Previous intravenous digitalis medication can contribute to complicated arrhythmias with idioventricular rhythm 5
- Atropine can accelerate the idioventricular rate in some patients with complete heart block 6
Metabolic and Systemic Factors
- Electrolyte imbalances (particularly in the context of digitalis toxicity) 5
- Subarachnoid hemorrhage and other central nervous system abnormalities 4
- Autonomic influences, as the rhythm accelerates with exercise suggesting autonomic control 4
Idiopathic (No Structural Heart Disease)
- Can occur in adults or children without structural heart disease 2
- Accelerated idioventricular rhythm can be found in otherwise healthy newborns and infants, usually as a coincidental finding 1
- In infants, it is a benign arrhythmia that generally disappears without treatment in the first year of life 1
- Reported in asymptomatic patients without demonstrable heart disease, suggesting a good prognosis 4
Mechanistic Considerations
Rate-Related Factors
- The dominant sinus rhythm rate in patients with idioventricular rhythm is significantly slower than in patients without this arrhythmia 3
- Frequently preceded by late ventricular extrasystoles with variation in coupling intervals 3
- Double ventricular extrasystoles separated by ≥600 ms can be precursors 3
Escape vs. Accelerated Mechanism
- Can function as an escape rhythm when the sinus rate slows 3
- More commonly represents an accelerated rhythm with enhanced automaticity 3
- The rhythm shows spontaneous changes in cycle length 3
Clinical Context and Risk Stratification
The rate of idioventricular rhythm correlates with risk: rhythms below 75/minute are considered benign, while rapid idioventricular rhythm (75-120/minute) has a significant association with ventricular tachycardia 3. Irregular idioventricular rhythm frequently accelerates to ventricular tachycardia 3.