An example of ventricular tachycardia in Lead II.  This patient's rate is about 190/min.  V Tach will have the following criteria:  Rate greater than 100/min, QRS duration greater than .12 sec. (120 ms), and no P wave associated with the QRS.

It can be difficult to distinguish V Tach from other wide-complex tachycardias without a 12-lead ECG, but all wide-complex tachycardias should be treated as V Tach until proven otherwise, as V Tach is a potentially lethal dysrhythmia.  V Tach can cause a severe reduction in cardiac output which can lead to V Fib and death.