Results
123 consecutive cases of DGCV VAs undergoing mapping and ablation in our center were retrospectively reviewed in this study, shown inFigure 3 . NS approach and SS approach were attempted in 123 cases and 79 cases respectively. By NS approach, DGCV-AIV target site reaching was obtained in 44 VAs (35.87%, 44/123) with successful ablation in 38 VAs (30.89%, 38/123) VAs. Via SS approach, DGCV-AIV target site reaching was obtained in 69 VAs (87.34%, 69/79) with successful ablation in 67 VAs (84.81%, 67/79). In 12 VAs, target sites failed to be reached by both NS approach and SS approach, the hydrophilic coated guidewire and Jukin’s-4 left coronary angiographic catheter-induced deep engagement of Swartz sheath was applied. By this way, the irrigated catheter was delivered to distal sites of DGCV-AIV. Among these 12 VAs, target sites was achieved in 7VAs (58.33%, 7/12) with successful ablation in 5 cases (41.67%, 5/12). There were no significant differences in catheter tip reaching coronary sinus, proximal GCV, middle GCV by NS approach and SS approach. Of note, some distal sites of GCV (DGCV1, DGCV2, AIV, Summit-CV) could be more possibly reached by catheter tip via SS approach. A successful ablation case of DGCV-AIV VAs by SS approach post failed NS approach was shown in Figure 4.
Due to the obstacle of venous valves of CVS, middle GCV could not be reached in 13 VAs and in 7 VAs by NS approach and SS approach, respectively. Nevertheless, via hydrophilic coated guide wire and coronary angiograohic catheter-guided deep engagement of Swartz sheath, the obstacle of venous valve was overcome. Hydrophilic coated guide wire could easily go through the venous valves, angiographic catheter went along super smooth guidewire, which provided a backup force for Swartz sheath and facilitate the Swartz sheath reach the middle GCV.
By NS approach, catheter tip accessed DGCV2 in 43 patients, among which, catheter tip could achieve AIV in only 21 patients. Via SS approach, catheter tip accessed DGCV2 in 69 patients, and catheter tip could further achieve AIV in 30 patients. The patients with AIV reached by catheter tip were compared with the patients of AIV not reached (51 VAs: 72.05±14.62° vs 61 VAs: 108.73±17.61°). The angel between AIV and DGCV2 ≤83° had a sensitivity of 94.1%, specificity of 77.0%, and accuracy of 94.5% for identifying the inaccessibility from DGCV2 to AIV, no matter SS approach or NS approached used, shown in Figure2 .
Whether the GCV morphology would affect the catheter manipulation approach selected was also investigated. In 44 VAs with target sites reached by NS approach, a smaller Width/Height of CVS was more found. On the contrary, in 67 VAs with target sites reached by SS approach, a relative larger Width/Height of CVS was observed. A W/H of CVS>0.69 had a sensitivity of 91.0%, specificity of 68.2%, and accuracy of 87% for identifying a SS approach application, shown in Figure2 .