Supra Ventricular Tachycardias are often not considered as dangerous as ventricular tachycardias. Non-Sustaining Ventricular Tachycardia reportedly happens in younger, healthy hearts too (but not often). But those that seem to get bouts of SVT only tolerate them for X amount of time before going to the ER to have the episode terminated. How long does your episodes last, and has your doctor provided a trigger point where you should seek medical assistance? Have you had a stress test to observe their occurrence under stress on your heart?