- SVTs are supraventricular tachycardias, that can be either atrial tachydysrhythmias (such as atrial fibrillation) or atrioventricular tachydysrhythmias. This document concerns the latter.
- Atrioventricular tachydysrhythmias arise from an abnormal impulse produced by, or dependent on, the AV node.
Types of atrioventricular tachydysrhythmia
- AV nodal reentrant tachycardia (AVNRT) (most common form, >50%); involves a reentrant circuit in the AV node itself
- AV reentrant tachycardia (AVRT); involves a reentrant circuit formed by aberrant myocardial accessory pathways between the atria and ventricles. Conduction may be orthodromic or antedromic down the normal His-Purkinje pathway, the latter tends to produce a wide QRS complex.
- Junctional ectopic tachycardia (rare)
- Nonparoxysmal junctional tachycardia (rare)
AVNRT; associated with:
- Myocardial ischemia
- Rheumatoid heart disease
- Mitral valve prolapse
- Medications, poisoning and toxic exposures (e.g. caffeine, theophylline)
AVRT; associated with:
- Presence of an accessory tract, often with evidence of a preexcitation syndrome on the baseline ECG (e.g. Lown-Ganong-Levine syndrome)
- Ebstein’s anomaly
Junctional ectopic tachycardia and nonparoxysmal junctional tachycardia
- Cardiac ischemia
- Digoxin toxicity
- Cardiac surgery
Consider secondary causes of tachycardia