Discussion
This is the first and largest study to report the safety and efficacy of
the mapping of atrial arrhythmias using the planar ‘grid’ design. The
novel organization of electrodes allows for multidirectional
determination of signal conduction that has not been previously
available from other HD mapping catheters through the simultaneous
recording of electrograms in multiple bipolar
orientations.1 The use of fixed 3mm equidistant
electrodes in a two-dimensional square organization allows
bi-directional and omnipolar interpretations of signal conduction both
along and across the splines. This unique feature contrasts from other
non-spiral multi-spline mapping catheters that adopt flexible spline
arrangements. Notably, the continuous fluctuations of electrode
distances between splines in these catheters may compromise the
integrity of voltage maps collected due to minute discrepancies in
wavefront interpretations. In addition, the grid design does not allow
for deformation and crowding of electrodes that results in some
mathematical benefit to putative rotor mapping during atrial
fibrillation, allowing an increase in atrial area covered for possible
rotor identification.2 However, to the best of our
knowledge, the new design catheter has been largely absent in large case
series and real-world efficacy and risk associated with the Grid design
are not reported.
After initial use in more complex cases, our operators quickly became
familiar with the handling and performance of the new design and its use
became first-line in the majority of patients. Given that the planar
design does not conform to the circular fit of most catheters used for
mapping pulmonary veins, one might question the role in pulmonary vein
mapping and isolation. We found the use of the catheter did not
compromise acute procedural success and during long-term follow-up we
observed low recurrence rates. Complications reported in our case series
are low and in keeping with contemporary data on complications and
risks. The pericardial tamponade occurred after the catheter ablation
and remote from mapping. Both incidents of cerebral ischemic insult
occurred in long standing (2.9 and 3.3 years) persistent atrial
fibrillation patients with cardiomyopathy and severe left atrial (LA)
enlargement (46.4 and 48.1 ml/m2). Previous studies
have demonstrated an independent association of mortality with increased
LA volume index after 5-year follow-up, with a 2.4 relative risk of
stroke for every 10-mm increase in LA size.3,4 We did
not attribute these complications to the novel catheter design
particularly, as one patient omitted oral anticoagulation for several
days post discharge.
A possibility of recurrence due to inadequate mapping in significant LA
enlargement rather than ablation failure was not observed in our patient
cohort, as there were no significant differences in LA volume and size
observed in the reported recurrent arrhythmia cases. Acute procedural
success was reported in all patients, supporting the use of the HD Grid
as a mapping tool. Our rate of arrhythmia recurrence (21.3%) is similar
to rates previously described by multiple circular mapping catheter
studies (21% and 26%).5,6
The low rates of complications reported in the current study (2.0%)
demonstrate comparable levels of mapping safety to established
circumferential pulmonary vein ablations using traditional circular
mapping catheters (3.5%) with similar reports of complications causes
including stroke and cardiac tamponade.7 Cardiac
tamponade arising due to the use of contact force-sensing catheters
remains low in our study (0.67%) and is consistent with the low
incidence of tamponade in non-contact force catheters
(0.44%).8
The highest recurrence rate reported from atrial tachycardia was
somewhat surprising given the potential advantages of the mapping
technology and catheter. However, these patients were a mixed bag of
incisional atrial tachycardia and focal sources. Recurrence in 6 of the
7 cases were classified with the same type of arrhythmia, suggesting a
failure of ablation strategy rather than diagnosis and mapping. The
group collectively had shorter procedure and ablation times, with one
case reported to have observed only 10 seconds of RF lesions to achieve
termination of tachycardia, therefore no further lesions were delivered.
Recurrence was mapped to the same location and longer ablation was
delivered to achieve durable success.