The difference between the postpacing interval (PPI) and the tachycardia cycle length (TCL; PPI−TCL) is a useful tool in mapping macro-reentrant tachycardias. However, entrainment pacing causes some perturbation of the conduction velocity within the tachycardia circuit, which may affect the repeatability and consequently the accuracy of the measurement of PPI−TCL. The aim of this study was to assess PPI−TCL repeatability both in vivo and in silico.Methods and Results—
In the experimental part, entrainment pacing was performed twice at each of the 124 tested sites for 30 patients undergoing radiofrequency ablation of atrial and ventricular re-entrant arrhythmias. A similar protocol was used in a simplified computer model of the cardiac tachycardia circuit in a 2-dimensional tissue strip using a Fenton–Karma model of cardiac tissue. In vivo, in the case of fast tachycardias (<350 ms), PPI−TCL variability observed was doubled compared with slow tachycardias (>350 ms; 95% Limits of Agreement ranged from −21.4 to 21.6 ms for TCL<350 ms and from −10.8 to 11.5 ms for TCL>350 ms). Simulations show that this increase of variability may be because of the oscillations of the conduction velocity inside the tachycardia circuits. The effect of the restitution properties of cardiac tissue on the outcome of entrainment pacing is discussed.Conclusions—
PPI−TCL is characterized by a high repeatability with the differences between the results for individual stimulations of ≤20 ms. The variability of this parameter is significantly lower in the case of slow tachycardias.