Patient Characteristics and Map Segments Obtained
The characteristics of all patients recruited to the study are outlined
in table 1. One patient (patient 9) was excluded from analysis as only
organised atrial tachycardia could be induced when attending for the
procedure. In all but one patient (patient 12), two 30-second maps of AF
were obtained at baseline. Patient 12 had varying QRS morphology as a
result of left bundle branch block and only one 30s segment could be
obtained with sufficient quality of QRS-T wave subtraction to allow
analysis. Maps following pulmonary vein isolation were obtained in 12
patients and a further 8 recordings were obtained following
non-pulmonary vein ablation providing a total of 62 simultaneous AF
recordings in the left and right atrium. Mapping duration and temporal
variability analysis was performed on all maps obtained (a total of 124
maps including both chambers). Spatial variability analysis was
performed by comparing the two 30s maps obtained at baseline in the 20
patients.
Spatial Variability
LIA demonstrated the greatest spatial stability with
R2 of 0.83(0.71-0.88) across all maps analysed. This
was consistent across both chambers with values of 0.81(0.75-0.88) and
0.84(0.61-0.88) in the LA and RA respectively. Median
R2 for LRA and FF were 0.39(0.24-0.57) and
0.64(0.54-0.73) respectively. Multiple low frequency focal firings were
seen widely distributed across the atrial surface (see figure 5). For
high frequency FF, defined as occurring ≥10 times over the 30s,
R2 was 0.83(0.68-0.85). Detailed results are outlined
in table 2.
Stability of regions across both maps with the highest frequency
patterns identified at 30% cut off was also greatest for LIA in both
the LA and RA. Cohen kappa statistic for LIA in the LA and RA
respectively was 0.75 (0.64-0.78) and 0.75 (0.58-0.79). Full kappa
statistic results for all patients are outlined in table 3.
The anatomical regions with maximal LIA were the anterior and posterior
LA (in 46% and 27% of maps respectively) and the lateral and septal RA
(in 46% and 32% respectively). LRA showed similar distribution with
the zone of highest LRA frequency in the posterior LA in 41% and the
anterior LA in 34%. In the RA, the lateral wall was the most common
site (in 37%) followed by the septum and posterior walls (each in
24%). A similar distribution was observed for FF, most commonly
involving the anterior and posterior LA (in 34% and 29% respectively),
followed by the LA septum (20%). In the RA, the highest frequency of FF
was seen in the septum in 59% and the lateral wall in 22%.