In entrainment mapping, a pacing result with no fusion and a PPI equal to TCL indicates:

In entrainment mapping, a pacing result with no fusion and a PPI equal to TCL indicates:

• A. Concealed entrainment
• B. Manifest entrainment
• C. Non-entrained
• D. Exit block

Answer: (A)

In entrainment mapping, the key is where the pacing impulse fits relative to the reentrant circuit. When you pace during tachycardia and there is no visible fusion on the surface ECG, but the post-pacing interval is the same as the tachycardia cycle length, it means the stimulus is entering and circulating entirely within the reentrant circuit without producing a new activation pattern on the outside myocardium. That is concealed entrainment: the pacing is inside the circuit and the tachycardia continues with the same QRS morphology because the captured impulse doesn’t create a separate fusion beat. If you had visible fusion, that would be manifest entrainment, indicating the pacing is influencing outside tissue as well. If pacing didn’t alter the tachycardia or the PPI wasn’t equal to the TCL, other scenarios like non-entrainment or exit block would be at play.

In entrainment mapping, the key is where the pacing impulse fits relative to the reentrant circuit. When you pace during tachycardia and there is no visible fusion on the surface ECG, but the post-pacing interval is the same as the tachycardia cycle length, it means the stimulus is entering and circulating entirely within the reentrant circuit without producing a new activation pattern on the outside myocardium. That is concealed entrainment: the pacing is inside the circuit and the tachycardia continues with the same QRS morphology because the captured impulse doesn’t create a separate fusion beat. If you had visible fusion, that would be manifest entrainment, indicating the pacing is influencing outside tissue as well. If pacing didn’t alter the tachycardia or the PPI wasn’t equal to the TCL, other scenarios like non-entrainment or exit block would be at play.