- (associatted with malignant V tach/ Torsades) QT : Nl QT=.39*[Sqr rt:RR; QTc = QTmeas/[Sqr rt:RR; nl<.45; 
- Class I 
- quinidine
- Procainamide 
- Tricyclics
- Phenthiazines 
- Disopyramide
- Amiodarone 
- Hypokalemia, 
- Hypocalcemia; 
- ? Digoxin Causes of QT Shortening: 
- ? Digoxin - Hyper Ca