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.