Table 1.

Clinical features suggesting arrhythmia mechanism.

Reentrant tachycardia	Automatic tachycardia	Triggered arrhythmia
•Regular rate or stable tachycardia cycle length •Paroxysmal, with abrupt onset and abrupt termination •Induced by programmed stimulation •Terminated by direct current (DC) shock or rapid overdrive pacing •Predictable slowing or termination with antiarrhythmic drugs that alter conduction through the tissue involved (e.g., Adenosine) •Amenable to ablation of one critical limb	•Wide variation in rate that correlates with autonomic tone •Gradual “warm-up” and “cool-down” of rates, at times incessant •Typically active during periods of high sympathetic tone. Cannot be induced by programmed stimulation •Inability to terminate with DC shock. Transiently suppressed by overdrive pacing. •Identified as focal disorder by intracardiac mapping, can be eliminated by ablation lesion at the epicenter of electrical activation	•Broad overlap with other mechanisms •Rate variation with warm-up and cool-down, sensitivity to catecholamines •Ability to induce and terminate with programmed stimulation or prolonged rapid pacing as well as termination with DC cardioversion. •In clinical practice, often identified by features not typical of either automaticity or reentry