50 year old female complaining of frequent AICD shocks

After 4 shocks over an hour from her 2 year old automatic internal cardiac defibrillator (AICD), the patient called an ambulance. On arrival to the ED, she explains that she gets VT but says that she doesn't know why and it generally only makes her feel a bit dizzy for the first 20 minutes or so. This time however, she had passed out each time before she was shocked.
She is sent to cardiology and her chart reveals her to have Idiopathic VT and the only treatment provided was the AICD.

A 12 lead ECG if found from a previous admission...

 

 a new one is is performed, and...

 

 12 lead ECG monitoring by your friends in the cardiac sciences department catch the arrhythmia brilliantly (in both standard 25mm/s...

 

  and slow 100mm/s format.

What are your thoughts?
What is the tachycardia?
From the first two ECGs, can you guess a likely diagnosis/cause of this lady's tachyarrhythmia?
And for the electrophysiologists in the audience, where is this arrhythmia arising from?