It is usually a regular, wide complex tachycardia with a rate between 120 and 250 beats per minute. A medically significant subvariant of ventricular tachycardia is called torsades de pointes (literally meaning "twisting of the points", due to its appearance on an EKG), which tends to result from a long QT interval.Both of these rhythms normally last for only a few seconds to minutes (paroxysmal tachycardia), but if VT persists it is extremely dangerous, often leading to ventricular fibrillation. Supraventricular
This is a type of tachycardia that originates from above the ventricles, such as the atria. It is sometimes known as paroxysmal atrial tachycardia (PAT). Several types of supraventricular tachycardia are known to exist. Atrial fibrillation
Atrial fibrillation is one of the most common cardiac arrhythmias. In general, it is an irregular, narrow complex rhythm. However, it may show wide QRS complexes on the ECG if a bundle branch block is present. At high rates, the QRS complex may also become wide due to the Ashman phenomenon. It may be difficult to determine the rhythms regularity when the rate exceeds 150 beats per minute. Depending on the patients health and other variables such as medications taken for rate control, atrial fibrillation may cause heart rates that span from 50 to 250 beats per minute (or even higher if an accessory pathway is present). However, new-onset atrial fibrillation tends to present with rates between 100 and 150 beats per minute. AV nodal reentrant tachycardia
AV nodal reentrant tachycardia (AVNRT) is the most common reentrant tachycardia.
It is a regular narrow complex tachycardia that usually responds well to the Valsalva maneuver or the drug adenosine. However, unstable patients sometimes require synchronized cardioversion. Definitive care may include catheter ablation. AV reentrant tachycardia
AV reentrant tachycardia (AVRT) requires an accessory pathway for its maintenance. AVRT may involve orthodromic conduction (where the impulse travels down the AV node to the ventricles and back up to the atria through the accessory pathway) or antidromic conduction (which the impulse travels down the accessory pathway and back up to the atria through the AV node). Orthodromic conduction usually results in a narrow complex tachycardia, and antidromic conduction usually results in a wide complex tachycardia that often mimics ventricular tachycardia. Most antiarrhythmics are contraindicated in the emergency treatment of AVRT, because they may paradoxically increase conduction across the accessory pathway. Junctional tachycardia
Junctional tachycardia is an automatic tachycardia originating in the AV junction. It tends to be a regular, narrow complex tachycardia and may be a sign of digitalis toxicity. Management
The management of tachycardia depends on its type (wide complex versus narrow complex), whether or not the person is stable or unstable, and whether the instability is due to the tachycardia. Unstable means that either important organ functions are affected or cardiac arrest is about to occur. Unstable
In those that are unstable with a narrow complex tachycardia, intravenous adenosine may be attempted. In all others immediate cardioversion is recommended.