2.5 Conduction velocity (CV) measurement
After the construction of the LAT map and the confirmation of the PMF diagnosis, a careful observation of the propagation map was carried out in order to identify areas with apparent delay throughout the whole wavefront course in a complete tachycardia circle. In these areas, a manual point correction was carried out at each received point, by locating the first deflection of the local electrogram. The timing scale was set either by spreading the color palette over the entire CL of the tachycardia or by defining color changing steps of 20 ms. In the derived map the shortest transverse distance in the direction of the wavefront propagation of an isochronal step was measured. For CV measurement, this distance was divided by the time interval of isochronal step and expressed in m/s. From the analyzed areas, the sites with the lower CV were pointed out. In the inspection of the propagation map, channels of conduction with a width ≤1 cm were sought, and the impulse CV was also measured in these channels. Eligible for this analysis were maps containing more than 2,000 points with sufficient dispersion throughout the circuit course.
Follow-up
After ablation, antiarrhythmic drugs could be administered at the discretion of the electrophysiologists for a period of 2-3 months. Anticoagulants were continued for the first 2-3 months and stopped when the CHA2DS2VASC score was < 1. All patients underwent follow-up at 1, 3, 6, and 12 months following the ablation procedure and yearly thereafter. During the entire post-procedural period, the patients were also followed by their referring physicians. Subsequent information was obtained by phone and/or e-mail. Follow-up visits included clinical examination, an ECG recording, and 24-h Holter monitoring. Tachycardia recurrence was defined as any atrial tachyarrhythmia (AT or AF) episode lasting ≥ 30 s documented in an ECG or Holter recording or during interrogation of an implantable cardiac rhythm device. A 3-month time interval after MI ablation was defined as blanking period.
Statistical analysis
Continuous variables are summarized as mean ± standard deviation (SD) or as median (interquartile range) according to data normality and were compared using Student’s t test or Mann-Whitney rank-sum test, as appropriate. Categorical data are summarized as frequencies and percentages and were compared using Pearson Chi-squared test and Fisher’s exact test. Between-group differences were assessed using one-way ANOVA or the Kruskal-Wallis test, according to data normality. Rates for freedom from arrhythmia recurrence were determined using Kaplan-Meier analysis and were compared by the log-rank test across groups. Data analyses were performed using IBM SPSS Statistics version 25 (Armonk, NY, USA). A p value < 0.05 was considered statistically significant.