The stretch and strain experienced by the action potential’s left shoulder region is almost similar* in both long and short QT syndromes that trigger a VT.(* Hope this explanation makes some electrical sense !)
*Click over the image for high resolution
What is short QT interval ?
It is a range . Any thing less than 380 ms can be considered short.Generally It becomes important only at < 320ms.
Relationship between QTc and risk of VT .
Dr.S.Venkatesan MD 