Overcoming High Impedance in the Transitional Area of the Distal Great Cardiac Vein during Radiofrequency Catheter Ablation of Ventricular Arrhythmia

Abstract

(1) Background: Radiofrequency catheter ablation (RFCA) is an essential treatment for ventricular arrhythmia (VA). However, high impedance in the transitional area of the distal great cardiac vein (TAODGCV) often leads to ablation failure. This study aimed to explore the factors influencing impedance and identify effective ways to reduce impedance. (2) Methods: A total of 156 patients with VA arising from the TAODGCV received RFCA therapy at our center from October 2009 to August 2021 and were retrospectively analyzed. Local impedance variation during RFCA was monitored, recorded, and analyzed. (3) Results: The impedance increased from the proximal to distal portions of the TAODGCV and decreased by increasing the saline flow rate at the same site. To overcome high impedance, we implemented the following strategies: (1) Reset the upper limit impedance to 300 Ω and accelerate the saline flow rate to 60 mL/min (effective in 118 of 144 patients); (2) turn off the upper limit impedance (effective in eleven of 21 patients); (3) use high-flow-rate irrigation devices (effective in five of 15 patients); and (4) increase the upper limit temperature (effective in six of ten patients). (4) Conclusions: In the TAODGCV, local impedance is mainly influenced by the target site location and saline flow rate. We concluded several methods to overcome the high impedance and contribute to a successful ablation.

Keywords: Impedance; distal great cardiac vein; electrophysiology; radiofrequency catheter ablation; ventricular arrhythmia.

Figure 1

The CVG and electrocardiogram of typical cases. (A1–A4) shows that the catheter tip reached Summit-CV via the Swartz sheath support approach. (B1–B4) shows the catheter tip inserted to AIV directly. (C) Sample electrocardiogram of a successful ablation of PVC originating from DGCV2. RFon indicates the beginning of radiofrequency energy delivery. The RF energy was delivered at the limit temperature of 43 °C, power of 30 W with a 60 mL/min saline flow rates.

Figure 2

The impedance in different parts of the TAODGCV. The above impedance values were measured at the initial state (saline flow rate was 2 mL/min).

Figure 3

The average impedance under the different saline flow rates. DGCV2 = distal great cardiac vein 2; AIV = anterior interventricular vein; Summit-CV = summit communicating vein at the top of the left ventricle.

Figure 4

The ablation process of patients with TAODGCV-VA. TAODGCV-VA = =ventricular arrhythmia originating from the transitional area of the distal great cardiac vein; LAD = left anterior descending coronary artery. * Ineffective means does not meet the standard of effective ablation (VA is terminated and cannot be induced by intravenous administration of isoproterenol and programmed stimulation, which usually requires energy delivery >20 W and lasting >30 s). # Ineffective because the spontaneous cut-off caused by the sharp impedance increase during ablation.

Figure 5

The X-ray imaging and anatomy of TAODGCV. (A,B) are the X-ray imaging of TAODGCV. (C,D) are anatomical diagrams of TAODGCV. The red ovals indicate the range of DGCV1 and DGCV2 defined in this study. TAODGCV = transitional area of the distal great cardiac vein; DGCV1 = distal great cardiac vein 1; DGCV2 = distal great cardiac vein 2; GCV = great cardiac vein; AIV = anterior interventricular vein; Summit-CV = summit communicating vein at the top of the left ventricle; TA = tricuspid annulus; MA = mitral annulus; ALV = anterior lateral vein; LAO = left anterior oblique position; RAO = right anterior oblique position.