Feasibility of SVCI in patients with CIEDs
Several previous reports have shown the histological and
electrophysiological characteristics of the SVC. It has been
microscopically confirmed by autopsy of human hearts that the myocardial
sleeve of the SVC only extends approximately 1.5 cm from the
RA15; however, many previous reports have demonstrated
arrhythmogenicity of the SVC.16-18 In contrast, the
electrical potential of the SVC has been recorded approximately 4 cm
above the RA-SVC junction.19 Because breakthrough
points from the RA to the SVC are limited, circumferential RF
application is not always needed to achieve SVCI.20Therefore, RF applications to the site where the leads had been
positioned could be avoided in most cases. Recently, conduction patterns
between the SVC and the RA have been studied using ultra-high-resolution
mapping. A spontaneous conduction block line was observed in 50% of the
study patients, and the block line was mainly positioned from the lower
lateral wall to the higher anterior wall or from the lower
posterolateral wall to the higher mid-septal wall.19We confirmed that most of the leads passed through the lateral portion
of the SVC. This might explain why most of the leads did not become
obstacles for SVCI, which resulted in the high success rate for SVCI in
the CIED group. Electrical reconnection between the SVC and the RA was
observed in 9 of 12 patients who underwent the second session among the
CIED group. The reconnection sites corresponded with the SVC wall
contiguous to leads in all patients, which might have resulted from
insufficient RF application at the site closest to the CIED leads. SVCI
failed in 3 patients (8.8% of the study patients) after the final
ablation procedure, which indicated that the target myocardial sleeve
might have been in direct contact with CIED leads in these 3 patients.
One patient in whom SVCI failed in the first ablation session had a
dual-coil defibrillator lead. The SVC coil was located at the lateral
wall of the SVC with a long adhering lesion, which might result in the
electrical isolation failure of the SVC. (Figure 1A) Two patients in
whom electrical re-isolation of the SVC failed in the second ablation
session had leads with diameters of >2 mm. Therefore, leads
with a large diameter were associated with a large contact area to
target the myocardial sleeve of the SVC, which might result in SVCI
failure.