AVNRT entrainment results in PPI-TCL of what?

• A. <115 ms
• B. =115 ms
• C. Not determinable
• D. >115 ms

Answer: (D)

The main idea is that PPI-TCL shows how far your pacing site is from the reentrant circuit during entrainment. If you pace from inside the circuit, the return interval after pacing closely tracks the tachycardia cycle length, so PPI-TCL is small. If you pace from outside the circuit, there’s extra time as impulses travel back to the circuit before the tachycardia resumes, making the post-pacing interval longer than the tachycardia cycle length.

In AVNRT, the reentrant circuit sits in or near the AV node. Entrainment pacing from outside that circuit, such as from the ventricle, typically yields a PPI-TCL that is substantially longer than the tachycardia cycle length. A common threshold used is about 115 ms; when the PPI-TCL exceeds this, it suggests the pacing site is outside the circuit. Hence, AVNRT entrainment results are usually greater than 115 ms.