Focal tachycardia can originate from enhanced automaticity or triggered activity. which option correctly reflects this?

• A. Enhanced automaticity or triggered activity
• B. Macroreentry only
• C. Conduction block only
• D. Vagal stimulation only

Answer: (A)

Focal tachycardia comes from a single ectopic focus that fires independently, not from a broad circuit. Two main ways this happens are enhanced automaticity and triggered activity. Enhanced automaticity means a non-nodal tissue gains pacemaker-like activity and fires on its own at a rate faster than the surrounding tissue. Triggered activity involves afterdepolarizations that reach threshold and trigger impulses: early afterdepolarizations during the repolarization phase or delayed afterdepolarizations after repolarization can start a rapid, focused rhythm from that site.

The other options describe mechanisms that don’t generate a focal source: a macroreentrant circuit requires a looping pathway, not a single ectopic focus; conduction block alone doesn’t produce a focal tachycardia; and vagal stimulation is autonomic input that modulates rate rather than creating the focal mechanism.