Localized bioelectrical conduction block from radiofrequency gastric ablation persists after healing: safety and feasibility in a recovery model

Pulsed-field ablation: an alternative ablative method for gastric electrophysiological intervention

Pulsed-field ablation (PFA) is an emerging ablative technology that has been used successfully to eliminate cardiac arrhythmias. As a nonthermal technique, it has significant benefits over traditional radiofrequency ablation with improved target tissue specificity and reduced risk of adverse events during cardiac applications. We investigated whether PFA is safe for use in the stomach and whether it could modulate gastric slow waves. Female weaner pigs were fasted overnight before anesthesia was induced using tiletamine hydrochloride (50 mg·mL-1) and zolazepam hydrochloride (50 mg·mL-1) and maintained with propofol (Diprivan 2%, 0.2-0.4 mg·kg-1·min-1). Pulsed-field ablation was performed on their gastric serosa in vivo. Adjacent point lesions (n = 2-4) were used to create a linear injury using bipolar pulsed-field ablation consisting of 40 pulses (10 Hz frequency, 0.1 ms pulse width, 1,000 V amplitude). High-resolution electrical mapping defined baseline and postablation gastric slow-wave patterns. A validated five-point scale was used to evaluate tissue damage in hematoxylin and eosin-stained images. Results indicated that PFA successfully induced complete conduction blocks in all cases, with lesions through the entire thickness of the gastric muscle layers. Consistent postablation slow-wave patterns emerged immediately following ablation and persisted over the study period. Pulsed-field ablation induces rapid conduction blocks as a tool to modulate slow-wave patterns, indicating it may be suitable as an alternative to radiofrequency ablation.NEW & NOTEWORTHY Results show that pulsed-field ablation can serve as a gastric slow-wave intervention by preventing slow-wave propagation across the lesion site. Stable conduction blocks were established immediately following energy delivery, faster than previous examples of radiofrequency gastric ablation. Pulsed-field ablation may be an alternative for gastric slow-wave intervention, and further functional and posthealing studies are now warranted.

Gastric slow-wave modulation via power-controlled, irrigated radio-frequency ablation

BACKGROUND

Recently, radio-frequency ablation has been used to modulate slow-wave activity in the porcine stomach. Gastric ablation is, however, still in its infancy compared to its history in the cardiac field, and electrophysiological studies have been restricted to temperature-controlled, non-irrigated ablation. Power-controlled, irrigated ablation may improve lesion formation at lower catheter-tip temperatures that produce the desired localized conduction block.

METHODS AND RESULTS

Power-controlled, irrigated radio-frequency ablation was performed on the gastric serosal surface of female weaner pigs (n = 5) in vivo. Three combinations of power (10-15 W) and irrigation settings (2-5 mL min-1) were investigated. A total of 12 linear lesions were created (n = 4 for each combination). Slow waves were recorded before and after ablation using high-resolution electrical mapping.

KEY RESULTS

Irrigation maintained catheter-tip temperature below 50°C. Ablation induced a complete conduction block in 8/12 cases (4/4 for 10 W at 2 mL min-1, 1/4 for 10 W at 5 mL min-1, 3/4 for 15 W at 5 mL min-1). Blocks were characterized by a decrease in signal amplitude at the lesion site, along with changes in slow-wave propagation patterns, where slow waves terminated at and/or rotated around the edge of the lesion.

CONCLUSIONS AND INFERENCES

Power-controlled, irrigated ablation can successfully modulate gastric slow-wave activity at a reduced catheter-tip temperature compared to temperature-controlled, non-irrigated ablation. Reducing the irrigation rate is more effective than increasing power for blocking slow-wave activity. These benefits suggest that irrigated ablation is a suitable option for further translation into a clinical intervention for gastric electrophysiology disorders.

Translation of an existing implantable cardiac monitoring device for measurement of gastric electrical slow-wave activity

BACKGROUND

Despite evidence that slow-wave dysrhythmia in the stomach is associated with clinical conditions such as gastroparesis and functional dyspepsia, there is still no widely available device for long-term monitoring of gastric electrical signals. Actionable biomarkers of gastrointestinal health are critically needed, and an implantable slow-wave monitoring device could aid in the establishment of causal relationships between symptoms and gastric electrophysiology. Recent developments in the area of wireless implantable gastric monitors demonstrate potential, but additional work and validation are required before this potential can be realized.

METHODS

We hypothesized that translating an existing implantable cardiac monitoring device, the Reveal LINQ™ (Medtronic), would present a more immediate solution. Following ethical approval and laparotomy in anesthetized pigs (n = 7), a Reveal LINQ was placed on the serosal surface of the stomach, immediately adjacent to a validated flexible-printed-circuit (FPC) electrical mapping array. Data were recorded for periods of 7.5 min, and the resultant signal characteristics from the FPC array and Reveal LINQ were compared.

KEY RESULTS

The Reveal LINQ device recorded slow waves in 6/7 subjects with a comparable period (p = 0.69), signal-to-noise ratio (p = 0.58), and downstroke width (p = 0.98) to the FPC, but with reduced amplitude (p = 0.024). Qualitatively, the Reveal LINQ slow-wave signal lacked the prolonged repolarization phase present in the FPC signals.

CONCLUSIONS & INFERENCES

These findings suggest that existing cardiac monitors may offer an efficient solution for the long-term monitoring of slow waves. Translation toward implantation now awaits.

Power-Controlled, Irrigated Radio-Frequency Ablation of Gastric Tissue: A Biophysical Analysis of Lesion Formation

BACKGROUND

Radio-frequency ablation of gastric tissue is in its infancy compared to its extensive history and use in the cardiac field.

AIMS

We employed power-controlled, irrigated radio-frequency ablation to create lesions on the serosal surface of the stomach to examine the impact of ablation power, irrigation, temperature, and impedance on lesion formation and tissue damage.

METHODS

A total of 160 lesions were created in vivo in female weaner pigs (n = 5) using a combination of four power levels (10, 15, 20, 30 W) at two irrigation rates (2, 5 mL min-1) and with one temperature-controlled (65 °C) reference setting previously validated for electrophysiological intervention in the stomach.

RESULTS

Power and irrigation rate combinations above 15 W resulted in lesions with significantly higher surface area and depth than the temperature-controlled setting. Irrigation resulted in significantly lower temperature (p < 0.001) and impedance (p < 0.001) compared to the temperature-controlled setting. No instances of perforation or tissue pop were recorded for any ablation sequence.

CONCLUSION

Power-controlled, irrigated radio-frequency ablation of gastric tissue is effective in creating larger and deeper lesions at reduced temperatures than previously investigated temperature-controlled radio-frequency ablation, highlighting a substantial improvement. These data define the biophysical impact of ablation parameters in gastric tissue, and they will guide future translation toward clinical application and in silico gastric ablation modeling. Combination of ablation settings (10-30 W power, 2-5 mL min-1 irrigation) were used to create serosal spot lesions. Histological analysis of lesions quantified localized tissue damage.

Anaesthesia by intravenous propofol reduces the incidence of intra-operative gastric electrical slow-wave dysrhythmias compared to isoflurane

Gastric motility is coordinated by bioelectrical slow-wave activity, and abnormal electrical dysrhythmias have been associated with nausea and vomiting. Studies have often been conducted under general anaesthesia, while the impact of general anaesthesia on slow-wave activity has not been studied. Clinical studies have shown that propofol anaesthesia reduces postoperative nausea and vomiting (PONV) compared with isoflurane, while the underlying mechanisms remain unclear. In this study, we investigated the effects of two anaesthetic drugs, intravenous (IV) propofol and volatile isoflurane, on slow-wave activity. In vivo experiments were performed in female weaner pigs (n = 24). Zolazepam and tiletamine were used to induce general anaesthesia, which was maintained using either IV propofol (n = 12) or isoflurane (n = 12). High-resolution electrical mapping of slow-wave activity was performed. Slow-wave dysrhythmias occurred less often in the propofol group, both in the duration of the recorded period that was dysrhythmic (propofol 14 ± 26%, isoflurane 43 ± 39%, P = 0.043 (Mann-Whitney U test)), and in a case-by-case basis (propofol 3/12, isoflurane 8/12, P = 0.015 (Chi-squared test)). Slow-wave amplitude was similar, while velocity and frequency were higher in the propofol group than the isoflurane group (P < 0.001 (Student's t-test)). This study presents a potential physiological biomarker linked to recent observations of reduced PONV with IV propofol. The results suggest that propofol is a more suitable anaesthetic for studying slow-wave patterns in vivo.