Anatomic obstacles for catheter manipulation in GCV
For catheter ablation of DGCV-AIV VAs, a thorough understanding of CVS anatomy is essential[1,2]. The coronary sinus is located at the posterior and inferior part of the epicardial mitral valve and collecting the blood from CVS, ends in the right atrium. There is a small folded tissue known as Thebesian valve at the ostium of the coronary sinus, which might occasionally be an obstacle to catheterization. A small left atrial vein named Marshall (or Marshall ligament) is the remnant of the embryonic left superior cardinal vein and drains into the coronary sinus. It is at the point where Marshall vein drains into coronary sinus that coronary sinus turns into the great cardiac vein, 29.15% of patients have a well-developed Vieussens valve at this site that might preclude ablation catheter advancement. The GCV goes along the lateral portions of the mitral valve and extends into DGCV at epicardium of the anterolateral portion of mitral annulus. It is reasonable to believe that a curved GCV morphology may limit the advancement of catheter. DGCV turns into AIV beneath the aortic valve cusp at the left ventricular summit. The angle between AIV and DGCV2 has great individual variability. It is observed that an acute angle between AIV and DGCV2 would prevent the ablation catheter reaching proximal AIV, on the contrary, an obtuse angle would facilitate catheter performing mapping and ablation in proximal AIV. Communicating vein refers to the very thin veins between the GCV and conus branch that drains to the small cardiac vein, and Summit-CV is a distinct CV that is located between the aortic and pulmonary annulus, distal to the transitional area between the GCV and the AIV, and in close association with the superior portion of the LV summit. Previous studies have revealed summit-CV can be the source of idiopathic ventricular arrhythmias. However, the very thin lumen of this vessel usually limits the detailed mapping and ablation in this region. Above all, hamper of venous valves (Thebesian valve and Vieussens valve), deflections of GCV, acute angle between DGCV and AIV, thin lumen of Summit-CV, are all potential anatomic factors preventing catheter ablation of DGCV-AIV VAs. Therefore, any method, which could assist ablation catheter overcoming these anatomic obstacles, would contribute to the successful ablation of DGCV-AIV VAs. Figure2 .
In this study, the angle between AIV and DGCV, and width/ height of GCV in each patient was measured by three electrophysiologists independently in the individualized LAO view (under this view, the course of GCV was sufficiently unfolded and clearly visualized), a mean value was adopted for statistical analysis. The height of GCV was defined as the maximal vertical distance from the beginning of AIV to the proximal GCV. The width of GCV was defined as maximal transversal distance from lateral GCV to the maximal vertical line.