Intrinsic cardiac or pulmonary disease
Metabolic derangements
Drug toxicity (including Digoxin)
Wandering atrial pacemaker
Intrinsic cardiac or pulmonary disease
Polymorphic ventricular tachycardia
Metabolic derangements
Accelerated idioventricular rhythm
Drug toxicity 
Narrow-complex tachycardia
Idiopathic fascicular left ventricular tachycardia