Entrainment With Long Postpacing Intervals From Within the Flutter Circuit

Long Postpacing Interval After Entrainment of Tachycardia Including a Slow Conduction Zone Within the Circuit

BACKGROUNDS

Postpacing interval (PPI) measured after entrainment pacing describes the distance between pacing site and reentrant circuit. However, the influential features to PPI remain to be elucidated.

METHODS AND RESULTS

This study included 22 cases with slow/fast atrioventricular (AV) nodal reentrant tachycardia (AVNRT), 14 orthodromic AV reciprocating tachycardia (AVRT) using an accessary pathway, 22 typical atrial flutter (AFL), and 18 other macroreentrant atrial tachycardia (atypical AFL). Rapid pacing at a pacing cycle length (PCL) 5% shorter than tachycardia cycle length (TCL) was done from a site on or close to the reentry circuit. Pacing sites included the coronary sinus ostium in AVNRT, earliest atrial activation site in AVRT, and cavotricuspid isthmus in typical AFL. In atypical AFL, tachycardia circuit was determined on the basis of CARTO mapping, and then the pacing site was. TCL was significantly longer in AVNRT and AVRT than in typical AFL and atypical AFL (both P < 0.05). PCL minus TCL value was similar among the 4 groups. PPI minus TCL value (milliseconds) was significantly longer in AVNRT (median, 40 [IQR, 29-60.8]) and AVRT (34 [20-47]) than in typical AFL (0 [0-4]) and atypical AFL (3.5 [0-8]) (both P < 0.05). Furthermore, PPI minus TCL was prolonged with shortening of PCL in AVNRT and AVRT (both P < 0.05), whereas it was unchanged in typical AFL (P = 0.50).

CONCLUSION

PPI after concealed entrainment is prolonged compared with TCL when the reentry circuit involves a slow conduction zone with a decremental conduction property such as the AV node.

Usefulness of entrainment mapping using the activation sequence of the last captured excitation in complex dual-loop atrial tachycardia

BACKGROUND

Electroanatomical mapping is useful for locating the atrial reentrant circuit, but analysis of the dynamic relation of the reentrant circuit is sometimes difficult. This article describes three cases of complex dual-loop reentrant atrial tachycardia analyzed by entrainment mapping using not only the postpacing interval (PPI) but also the activation sequence of the last captured beats.

METHODS

Case 1 was dual-loop reentry consisting of the tricuspid annulus (TA) and a localized atrial reentry at the coronary sinus (CS) ostium with different exit sites to the right and the left atrium that was cured by catheter ablation at the CS ostium showing fractionated potential. Case 2 was dual-loop reentry around the TA and the superior trans-septal incision line. Case 3 was dual-loop reentry around the TA and longitudinal dissociation along the cavo-tricuspid isthmus.

RESULTS

In Cases 1 and 2, entrainment with a shorter pacing cycle length demonstrated antidromic penetration to the circuit and changed the activation sequence of the last captured beat depending on the anatomical relation of the reentrant circuit. In Cases 1-3 with dual-loop reentry, the excitation wavefront induced by stimulation entered one circuit after going around the other; thus, the penetration to the other reentry circuit became the second beat after the stimulus (one lap behind).

CONCLUSIONS

The PPI is obtained from the pacing site only, but the last captured beat could be obtained from all electrodes. It is advantageous to use the information from all available electrode recordings to determine the dynamic relation between complex dual-loop reentrant circuits.