Triggered activity differs from automaticity in that it is not consistently spontaneous and can result in either a single or repetitive firing of myocardial cells caused by re-excitation. Late potentials during Phase 3 or 4 of the cardiac action potential can trigger afterdepolarizations, which can lead to ventricular arrhythmias. Reentry involves an impulse traveling through two pathways in the heart with different refractory periods, with the impulse reentering the first pathway after the second pathway recovers.
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