The catheter anatomical guidance facilitates ethanol ablation of ventricular arrhythmias from the left ventricular summit

Venous ethanol ablation (VEA) is effective for ablation-refractory ventricular arrhythmias (VAs), particularly those arising from the left ventricular (LV) summit and interventricular septum.¹ However, numerous intricate veins within this region make the accurate mapping technique challenging.² Despite the microelectrode or guidewire could be integrated within the three-dimensional electroanatomic mapping system, a venogram is mandatory to present the venous atlas. We aimed to evaluate whether the catheter guidance (CG) at the earliest endocardial site could facilitate identifying the optimal vein and the procedure of VEA.

We retrospectively enrolled 28 patients with radiofrequency ablation (RFA) refractory ventricular tachycardia (VT) or premature ventricular contractions (PVCs) who underwent VEA between February 2022 and December 2023 in Fuwai Hospital, China. The VAs all met the criteria of intramural origins.³ All patients consent to study participation. The study was approved by the institutional Ethics Committee (NO. 2023-1976).

Before VEA, all the patients underwent mapping and ablation using a 3.5 mm irrigated catheter. If the VAs were suppressed within 15 s, the energy application was maintained for 60–90 s with a maximum power of 50 W in the endocardium. Ablation in the great cardiac vein/anterior interventricular vein (GCV/AIV) was limited to 30 s and 20 W with an irrigation speed of 30 mL/s. Also, anatomical ablation on the opposite endocardial side was attempted.

Patients with refractory VAs were treated with venous mapping and VEA as previously described.⁴ If there was obvious presystolic potential (≥15 ms) in the endocardial site, the ablation catheter was positioned at the earliest endocardial activation site during angiography, and those patients were classified into the CG group. The vein nearest the catheter tip was initially mapped, requiring verification from at least two projections: left anterior oblique at 45° and right anterior oblique at 30°. Additional caudal or cranial projections were used if there was significant overlap. If no presystolic potential was detected in any chamber or catheter positioning was unstable, venous angiography and VEA proceeded without CG, classifying as the ‘non-CG group’. After coronary venous angiography, the guidewire covered with a balloon was cannulated into the adjacent veins for mapping (Figure 1). A branch showing earlier activation than endocardial sites or the main trunk of GCV/AIV, with a ‘QS’ pattern in the unipolar signal, was considered a potential target vein. The 95% ethanol, up to 2 mL, was used for attempted ablation. If the initial ablation was effective, additional ethanol would be injected for consolidation. The total infusion volume was determined based on the size of myocardial staining, with a maximum of 6 mL in each vein. Otherwise, other veins in the LV summit region were mapped sequentially. Acute and 3-month success was defined as ≥80% reduction of PVC and no VT recurrence. Additionally, the total procedure time and fluoroscopy time were recorded.

Figure 1

Clinical outcomes of venous ethanol ablation with and without the catheter guidance in the endocardium. (A) Schematic of the catheter utilization in two groups. The branch closest to the catheter was apparent and proven to be the target vein with guidewire mapping. (B) The catheter guidance group demonstrated higher success rate, shorter procedural time, and less fluoroscopy exposure. Data are expressed as the percentage or median with interquartile (Q1, Q3). CG, catheter guidance; non-CG, non-catheter guidance; GCV/AIV, great cardiac vein/anterior interventricular vein; RVOT, right ventricular outflow tract.

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A total of 28 patients received VEA with or without the CG (CG group, n = 17; non-CG group, n = 11). The average PVC burden was 32% and 23 patients (82%) monitored monomorphic VT. Ten patients (36%) had previous failed procedures. The two groups showed no significant differences in clinical characteristics. The details of mapping and ablation are presented in Table 1. The acute success rate was significantly higher in the CG group than in the non-CG group (76.5% vs. 27.3%, P = 0.019). One patient recurred during follow-up, and the success rate at 3 months was 70.6% and 27.3% in the CG and non-CG groups (P = 0.025). The preceding activation time for the patient with recurrence was −30 ms, while the median time for those without recurrence was −20 ms. However, it is notable that the ethanol injection dose administered to this patient (6 mL) was lower than those who did not experience recurrence (median of 8.5 mL). The recurrence might be attributed to incomplete necrosis at the site of arrhythmia origin. The median procedural time (142 vs. 198 min, P = 0.004) and fluoroscopy time (25 vs. 32 min, P = 0.039) were significantly shorter in the CG group (Figure 1). No major complications occurred.

A prior study found nearly half of the LV summit VAs had the earliest ventricular activation from septal perforator veins. Only 11.3% could be successfully ablated from the opposite endocardial site with anatomic guidance using a guidewire in the coronary vein.⁵ The effectiveness of RFA might be limited by the prominent thickness of the ventricle wall. In contrast to the previous study, we utilized the CG at the earliest endocardial site and searched for the nearest vein for mapping and ethanol infusion. To our knowledge, the availability of the microelectrode is limited in many countries and electrophysiology (EP) laboratories. The visualization of tiny branches may only be achieved through angiography, and the guidewire is the only tool for venous mapping, while placing the catheter at the earliest endocardial ventricular activation site operators could predict the most probable location for VEA.

The first reason for the relatively low success rate in the non-CG group might be insufficient guidewire mapping due to the unknown target area. In this group, most cases (8/11) did not detect obvious presystolic signals in the endocardium. Mapping in the venous system simply with a guidewire might be inadequate and result in undetected identification of the target vein. The second reason might be no effective joint endocardial ablation. Half of the patients in the CG group (9/18) underwent endocardial ablation and achieved transient suppression, whereas only two patients in the non-CG group. The combination of RFA and VEA likely led to enhanced transmural lesions and improved clinical outcomes. The main limitation was the small sample size due to the rarity of this type of VAs.

Utilizing the catheter placed at the earliest endocardial site could provide crucial anatomic guidance in choosing the optimal vein for VEA, which may result in a higher success rate, shorter procedural time, and less fluoroscopy exposure.

Author contributions

Conceptualization: L.-J.M. and H.-D.Z.; data curation: L.-J.M., H.-D.Z., and K.Z.; formal analysis: L.-J.M., H.-D.Z., and J.L.; funding acquisition: H.-D.Z. and M.T.; methodology: L.-J.M., H.-D.Z., and L.D.; project administration and resources: M.T.; writing—original draft: L.M.; writing—review & editing: H.-D.Z., J.L., K.Z., L.D., F.Y., Z.J., and A.-K.Z. All the authors have read and agreed to the published version of the manuscript.

Funding

This study was supported by Chinese Academy of Medical Sciences (CAMS) Innovation Fund for Medical Sciences: 2022-I2M-C&T-B-047; Chinese Academy of Medical Sciences Innovation Fund for Medical Sciences: 2023-I2M-C&T-B-067; National High-Level Hospital Clinical Research Funding: 2023-GSP-GG-14.

Data availability

The data sets presented in this article are not readily available because research data are confidential. Requests to access the data sets should be directed to [email protected].

References

Author notes