Ablation and hydrogel injection in beating heart and approach to
cardiac mapping
Upon establishing the ex vivo suspension and stable function of
the heart, patches were attached around the basin to permit ex
vivo electroanatomical mapping (EAM; CARTO3 system, Biosense Webster,
Diamond Bar, CA, USA). A 3.5 mm tip irrigated ablation catheter
(ThermoCool Navistar; Biosense Webster, Diamond Bar, CA, USA) was used
to perform both mapping and focal ablation. First, during normal sinus
rhythm, point-by-point mapping of the epicardial surface of the lateral
left ventricle was performed. Each point was adjudicated to establish an
appropriate timing reference. After this, a point with homogeneous
conduction and voltage was selected within the mapped region as a target
for ablation at 30 Watts for 1 minute with normal saline irrigation at
30 ml/min. We then remapped the region including within the scar region
and around in regions of normal tissue. The hydrogel was then injected
using an 18-gauge needle by sequentially injecting circumferentially
around the area of ablated myocardium by pushing the needle into the
tissue and slowly injecting the hydrogel as it was withdrawn with each
injection. Injections were then performed in perpendicular lines spaced
evenly 1 mm apart through the center of the lesion in a grid pattern.
After this, remapping was done of the region with again careful
attention to annotation of individual points. The time between injection
and remapping was within minutes. All mapping was done during sinus
rhythm.