What is NSVT?

Answer 1

This is likely an abbreviation for "non-sustained ventricular tachycardia"

Sustained VT (or simply VT) is a fatal rhythm where the ventricles are essentially quivering instead of pumping. The heart is not able to pump in this rhythm, and unless the patient is shocked out of it (defibrillated) or brought out of it with drugs, death will follow shortly. NSVT is a short run of VT where the heart brings itself out of the rhythm without outside intervention.