What defines non-sustained ventricular tachycardia (NSVT) in clinical practice?
A. A heart rate of over 100 beats per minute lasting for at least 30 seconds
B. Episodes of rapid heart rate originating from the atria, lasting less than 10 seconds
C. Rapid heart rate originating from the ventricles, lasting less than 30 seconds and resolving spontaneously
D. A period of slow heart rate, followed by a rapid increase in heart rate, often caused by electrical impulses originating in the atria