I. Pathogenesis of atrial fibrillation For more than half a century, basic research workers and clinical cardiac electrophysiologists have unremittingly explored the possible pathogenesis of atrial fibrillation, and the research results achieved have strongly promoted the progress of atrial fibrillation treatment. However, there are still many unknown aspects about the pathogenesis of atrial fibrillation that need to be further explored. More than half a century ago, a possible mechanism for the development of AF was proposed as Multiple Wave Reentry, a theory that AF is triggered and maintained by the joint excitation of multiple independently propagating reentrant subwaves, and that the formation of multiple small reentrant loops depends on the slow conduction of atrial muscle and the inconsistency of atrial myocardial nonconductivity. Another possible mechanism of AF is the Trigger theory, which also first appeared in the 1950s; it was not until 1998 that Haissaguerre et al. suggested that atrial premature, atrial tachycardia, and atrial flutter of pulmonary vein origin accounted for nearly 90% of paroxysmal AF, which led to the modern catheter ablation. The Autonomic Nerve theory suggests that cardiac autonomic imbalance plays an important role in the development of both of these AF mechanisms. Increased sympathetic tone increases the ectopic excitability that induces atrial fibrillation, whereas vagal excitation shortens the effective atrial myocardial inactivity, both of which are more likely to promote the development of atrial fibrillation. Therefore, AF can also be classified into sympathetic and vagal-mediated types. In general, the trigger foci doctrine describes the triggering mechanism of AF, while the multiwave foldback is an important maintenance substrate (Substrate) for the development of AF. Autonomic nerve mediation, which is involved in the formation of ectopic foci of excitation and the triggering of AF, also plays an important role in the formation and maintenance of the multiwave foldback. Another theory of the maintenance mechanism of atrial fibrillation suggests that the multiwave foldback within the atria during atrial fibrillation is not completely disordered; several small microfoldbacks can trigger and drive a large foldback, which is also known as the dominant foldback loop or rotor, and several rotors can exist simultaneously in the left and right atria during atrial fibrillation, and the rotor encounters a functional or anatomical barrier when propagating within the atria to disperse more microfoldbacks, facilitating the induced atrial fibrillation and allows AF to be maintained. The latter is also referred to as the rotor or dominant foldback loop doctrine. These three aspects, triggering foci, multiwave foldback or rotor and autonomic nerves, are interacting and influencing each other in the development of AF, which is the Coumel’s Triangle Of Arrhythmogenesis theory first proposed by French scholar Philippe Coumel, organically integrating the above-mentioned pathogenesis of atrial fibrillation. The triangle of arrhythmogenesis proposed by Philippe Coumel The role of these pathogenesis theories is not identical in different stages of AF patients. In general, the trigger foci theory predominates in the early stages of paroxysmal AF, whereas the multiwave foldback and rotor theories may predominate in persistent and permanent AF. In addition, the role of autonomic mediation varies in different patients with atrial fibrillation at different stages of the disease course. Non-pharmacological treatments are most closely related to the mechanisms of AF, or different non-pharmacological treatments for AF are designed based on different theories of AF pathogenesis. In turn, the effectiveness of different nonpharmacologic treatments validates the different atrial fibrillation pathogenesis theories. The multi-wave foldback theory generally assumes that for AF to be maintained, there must be at least 6 to 7 small foldbacks in the atria, and each foldback loop needs to be supported by sufficient myocardial volume, i.e., the atria are large enough. The cardiac surgical maze procedure (Maze procedure), which was based on this academic theory, was successful in the late 1980s and early 1990s. The basic concept is that any small piece of atrial muscle divided by the Maze is not large enough to form a foldback, thus effectively preventing the development of atrial fibrillation; at the same time, the designed intra-atrial cutting lines guarantee the normal conduction of electrical activity originating from the sinus node within the atria and between the atria. The main limitations of the maze procedure are the complexity of the procedure and the perioperative mortality, and it is generally indicated mainly for patients with concomitant underlying cardiac disorders requiring surgical intervention. Current transcatheter ablation techniques sometimes improve the success rate of catheter ablation of persistent atrial fibrillation by adding linear ablation within the atria. In addition, one possible mechanism for atrial fractionated atrial electrograms (CFAE) and circumferential pulmonary vein ablation (CPVA) for the treatment of atrial fibrillation also involves partial modification of the atrial fibrillation maintenance substrate. modifications. However, the most important mechanism of circumpulmonary vein ablation for AF is the isolation of the pulmonary veins so that ectopic electrical activity originating from the pulmonary veins (including premature atrial rate, atrial tachycardia, atrial flutter, and atrial fibrillation) cannot be transmitted to the atria and is inhibited from inducing and driving AF. The results of both basic and clinical studies suggest that ablation of the autonomic plexus (Ganglionated plexi, GP) in the atria is also effective in preventing and reducing the occurrence of atrial fibrillation. The area of distribution of the autonomic plexus in the atria can be identified by endocardial high-frequency stimulation, and because of its relatively fixed anatomical location, usually around the pulmonary vein orifice, empirical ablation can also be performed at the most common site. The autonomic plexus is classified as superior right pulmonary vein, inferior right pulmonary vein, superior left pulmonary vein, and inferior left pulmonary vein autonomic plexus according to its location relative to the pulmonary veins. Recent studies have suggested that renal artery denervation ablation based on electrical isolation of the pulmonary veins in patients with combined hypertension is also beneficial in reducing the recurrence rate of postoperative atrial fibrillation by altering the autonomic function of the patient. The application of specially designed mesh-basket shaped multi-site labeling electrodes and computer processing technology can identify the rotor or driving foci (Focal Impulse And Rotor Modulation (FIRM)) in the atria during atrial fibrillation, and by ablating these sites, the occurrence of atrial fibrillation can also be prevented and reduced. Although several transcatheter atrial fibrillation ablation techniques have been devised according to different mechanisms of atrial fibrillation occurrence and formation, electrical isolation by circumferential pulmonary vein ablation remains the cornerstone of catheter ablation for atrial fibrillation. III. Causes of recurrence after transcatheter ablation of atrial fibrillation A gap period of 3 months after transcatheter ablation of atrial fibrillation, after which recurrence is generally defined as clinically significant. more than 90% of early recurrences of atrial fibrillation (within 1 year after surgery) are due to the recovery of electrical conduction between the pulmonary veins and the atria. The application of cold saline catheters, intraoperative assessment of the bi-directional conduction block in the circumferential pulmonary vein ablation line, and the application of adenosine and re-evaluation of the circumferential pulmonary vein ablation line after a certain period of observation can improve the “durability” of the circumferential pulmonary vein ablation line, mainly due to the inability to accurately evaluate intraoperatively whether the electrical connection between the pulmonary veins and the atria has been permanently blocked. “This can improve the durability of the ablation line, reduce the possibility of recovery of electrical conduction between the pulmonary veins and the cardiac chambers, and reduce the early recurrence of atrial fibrillation. Image fusion technology-guided individualized large-ring circumferential pulmonary vein ablation with electrical isolation can also improve the effectiveness of atrial fibrillation catheter ablation procedures because the ablation site is at the junction of the atrial and pulmonary vein vestibules, relatively closer to the atrial side, allowing for more isolation of the trigger foci and more improvement of the atrial fibrillation substrate. After catheter ablation, the main causes of late recurrence of AF (after 1 year post-procedure) include the formation of new ectopic foci of excitation outside the vein, triggering and driving AF, and progression of AF maintenance mechanisms. Atrial fibrillation is a progressive disease, and the HATCH score stratifies and scores patients with paroxysmal atrial fibrillation using hypertension (H: hypertension), age (A: age, 75 years), history of transient ischemic attack or stroke (T: TIA or stroke), chronic obstructive pulmonary disease (C: COPD), and heart failure (H: heart failure) The score was 2 for a history of transient ischemic attack or stroke and 1 for heart failure, and 1 for other risk factors. If a patient with paroxysmal AF has a HATCH score of 1 or 2, the risk of developing persistent AF within 1 year is 5-6%, whereas with a HATCH score of 6 or 7, the risk of developing persistent AF within 1 year is as high as 50%. In addition, diabetes and obesity are important influences on the progression of atrial fibrillation. Clinical studies have also found that patients with AF with higher HATCH scores have a higher recurrence rate after catheter ablation than those with lower scores, even after multiple catheter ablations. It has also been suggested that applying delayed enhancement magnetic resonance technique (DE-MRI) to quantify the degree of atrial fibrosis in patients with atrial fibrillation, mild fibrosis is defined as patients with atrial fibrosis of less than 15% of the entire atrial muscle, severe is defined as fibrosis of more than 35%, and moderate fibrosis is somewhere in between. Subgroup studies have shown that patients with atrial fibrillation with more severe fibrosis have a higher recurrence rate after ablation. All of these studies suggest that in addition to the transcatheter ablation technique for atrial fibrillation, the characteristics of the patient with atrial fibrillation itself, such as comorbid conditions and the degree of atrial fibrosis, are important factors that influence the effectiveness of catheter ablation for atrial fibrillation. To improve the effectiveness of catheter ablation for atrial fibrillation, recent studies suggest that catheter ablation should be performed early in patients with atrial fibrillation. The type of atrial fibrillation, the duration of atrial fibrillation, and the size of the left atrium are important factors that affect the effectiveness of catheter ablation for atrial fibrillation. In general, the effectiveness of catheter ablation in patients with paroxysmal AF is better than that in patients with persistent AF, and the longer the duration of persistent AF and the larger the left atrium, the higher the recurrence rate after catheter ablation. Based on these findings, both domestic and international guidelines for atrial fibrillation recommend that catheter ablation should be preferred for patients with symptomatic paroxysmal atrial fibrillation who have failed to respond to pharmacological therapy (recommendation category I, level of evidence A). IV. Summary Catheter ablation aims to prevent and reduce the occurrence of atrial fibrillation by removing and inhibiting the excitatory foci that induce atrial fibrillation, improving the substrate that maintains atrial fibrillation, and balancing the autonomic function from the mechanism of its occurrence. Because AF is a progressive disease, it is important to select the right population for the procedure and the time point for catheter ablation in order to improve the effectiveness of catheter ablation for AF. Catheter ablation should be actively performed in appropriate patients with atrial fibrillation, in experienced centers, and using reasonable catheter ablation techniques, which can bring significant improvements in symptoms and prognosis for patients with atrial fibrillation based on effective prevention and reduction of atrial fibrillation recurrence. As our understanding of the pathogenesis of atrial fibrillation continues to improve, and as catheter ablation techniques continue to improve, the effectiveness of catheter ablation for atrial fibrillation will continue to improve.