Inclusion Criteria:  Age between 18-80 years old EKG shows regular rhythm, narrow QRS complex tachyarrhythmias (QRS complex <0.12 msec, and rate >150 beats per minute; bpm) Pulse can be palpated The tachycardia is not terminated by a vagal maneuver.  Exclusion Criteria:  Acute asthmatic attack Pregnant or tendency to be pregnant Acute heart failure Acute chest pain Alteration of consciousness Hypotension Presenting of signs of hypoperfusion