There were many causes of AF with old age being an independent risk factor [9]. As the world population is aging, the number of AF patients is expected to continue to increase in the future, and the incidence of AF in China is approximately 0.77% [10]. AF can cause a variety of hazards, including thromboembolism and heart failure, which can seriously affect the physiological function of patients. It also imposes an economic burden on families and social health care to a certain extent. With the increasing prevalence and mortality of AF, it has been a major public health problem.
Radiofrequency ablation is an important method for maintaining sinus rhythm in patients with AF, especially those with symptomatic AF. The key to successful radiofrequency ablation is the formation of continuous and transmural tissue damage, which depends on the depth and extent of irreversible cellular damage caused at each ablation target. However, the success rate of AF operations, especially in terms of relieving patient pain after ablation, is currently suboptimal due to an incomplete understanding of the pathogenesis of AF and the limitations of radiofrequency ablation techniques. Although radiofrequency ablation therapy for AF has been developing and progressing in recent years, patients often have significant pain during ablation and even after surgery. Some researchers have concluded that the possible reason for pain in patients might be that the current ablation operation was basically performed in the left atrium, which had a relatively weak posterior wall and was adjacent to the tracheoesophageal [11]. Additionally, some researchers found by autopsy that the vagus nerve in the posterior wall of the left atrium was the most distributed and abundant, and the vagus nerve density was higher at the site of radiofrequency ablation, which might lead to injury sensitivity due to the uneven distribution of the vagus nerve in the left atrium [12]. This might better explain the fact that most of the painful points in radiofrequency ablation of AF were located in the posterior wall of the left atrium. To improve the short/long-term efficacy of radiofrequency ablation as well as to reduce the postoperative pain of patients, performing ablation by increasing the radiofrequency output power and reducing the ablation time point by point were proposed.
Although there were no uniform criteria regarding high- and low-power radiofrequency ablation operations, many studies have shown that high-power radiofrequency ablation could reduce adjacent tissue damage with significant advantages compared to low-power ablation. An animal study showed that ablation with output power/duration of 50W/5s and 60W/5s appeared to be more likely to achieve effective transmural injury without increasing surgical complications compared to that of 40W/30s [13]. Pambrun et al. found that high-power ablation (40-50W) was shallower in depth and wider in ablation diameter than low-power ablation (25-30W) [14]. The high-power ablation line had higher integrity and a wider damage range at the same depth of injury. It was also shown that the high-power ablation strategy could achieve adequate continuity without increasing the ablation depth. A study comparing the effects of different power ablation strategies on the degree of injury in isolated pig hearts under the same pressure conditions found that the ablation strategy of 50W/13s was sufficient to meet the needs of left atrial ablation, could minimize the damage to adjacent organs and tissues such as the left atrial posterior wall and esophagus, ensured good tightness and effective ablation depth between each target point, thus reducing pain [15]. To the best of our knowledge, this is one of the few studies in China to investigate the effect of different power radiofrequency ablations in treatment and postoperative pain in AF patients. The effectiveness of the high-power ablation strategy for the treatment of AF was confirmed in this study. There were no significant differences in the number of ablation points and some intraoperative electrophysiological indicators between different power groups. However, the high-power group was superior to the conventional power group in terms of total discharge time and pulmonary vein isolation time, suggesting that the high-power ablation strategy could further improve the surgical efficiency on the basis of effectiveness.
This study also analyzed the effect of radiofrequency ablation procedures with different powers on patients' postoperative pain. The results showed that high-power ablation reduced patients' immediate and late postoperative pain, which might be due to better continuity and shorter duration of the ablation process at a certain ablation range and depth, which was conducive to reducing tissue and nerve damage. As local anesthesia and fentanyl analgesia were used during radiofrequency ablation surgery in China, patients inevitably experienced pain, which could affect real-time catheter apposition, prolong the operation time, and reduce the effectiveness of ablation. The high-power ablation strategy seemed to increase patient comfort on the basis of better safety.
The findings in this study should be interpreted with consideration of the study limitations. Firstly, the sample was from a single hospital with a small sample size. A prospective study with a large sample size is needed in the future. Secondly, the surgical effect indicators were limited to the intraoperative period. Finally, postoperative pain was measured no more than 24 hours after surgery. A follow-up study could be conducted to determine the long-term effect of different power radiofrequency ablations in treatment and postoperative pain in AF patients.