[2] Ventricular tachycardia may lead to coma and persistent vegetative state due to lack of blood and oxygen to the brain.

[2][3] Diagnosis is by an electrocardiogram (ECG) showing a rate of greater than 120 beats per minute and at least three wide QRS complexes in a row.

[5] While waiting for a defibrillator, a precordial thump may be attempted (by those who have experience) in those on a heart monitor who are seen going into an unstable ventricular tachycardia.

[2] An implantable cardiac defibrillator or medications such as calcium channel blockers or amiodarone may be used to prevent recurrence.

Acquired problems are usually related to drug toxicity or electrolyte abnormalities, but can occur as a result of myocardial ischemia.

Class III anti-arrhythmic drugs such as sotalol and amiodarone prolong the QT interval and may in some circumstances be pro-arrhythmic.

This is particularly true if calcium channel blockers, such as verapamil, are used to attempt to terminate a presumed supraventricular tachycardia.

In this circumstance, it is best treated the same way as ventricular fibrillation (VF), and is recognized as one of the shockable rhythms on the cardiac arrest protocol.

The heart usually tolerates this rhythm poorly in the medium to long term, and patients may certainly deteriorate to pulseless VT or to VF.

This is known as idiopathic ventricular tachycardia and in the monomorphic form coincides with little or no increased risk of sudden cardiac death.

While the causes of idiopathic VT are not known, in general it is presumed to be congenital, and can be brought on by any number of diverse factors.

The shock may be delivered to the outside of the chest using the two pads of an external defibrillator, or internally to the heart by an implantable cardioverter-defibrillator (ICD) if one has previously been inserted.

If this fails after a short trial, the ICD will usually stop pacing, charge up and deliver a defibrillation grade shock.

Catheter ablation is a potentially definitive treatment option for those with recurrent VT.[18] Remote magnetic navigation is one effective method to do the procedure.

[19] In the past, ablation was often not considered until pharmacological options had been exhausted, often after the patient had developed substantial morbidity from recurrent episodes of VT and ICD shocks.

Antiarrhythmic medications can reduce the frequency of ICD therapies, but have efficacy varies and side effects can be significant.