supraventricular tachycardia maze procedure cryoablation SUPRAVENTRICULAR TACHYCARDIA An arrhythmia is an irregular heartbeat, a condition that affects more than 10 million people worldwide. The irregularity can be a heartbeat that is too fast (supraventricular tachycardia) or too slow (bradycardia), but it is caused by a change or interruption in the heart's normal reception and distribution of electrical impulses.