Introduction to Atrial FibrillationRapid, disorganized atrial contractionsRapid, irregular ventricular response to cardiac conduction–atrial fibrillationEpidemiologyAtrial fibrillation is one of the most common chronic or recurrent tachyarrhythmias in clinical practiceSun Zongquan, Department of Cardiac Surgery, Peking Union Medical College Hospital, WuhanPopulation incidence: 0.15-1.0%People over 60 years of age: 8-17 Patients with mitral valve disease: 79% of patients with cerebral thromboembolism, 33% of patients with AF. 60% die or become permanently disabled Epidemiology Worldwide number of people with AF In the mid-1990s, approximately 5.5 million people worldwide had AF, with a new diagnosis rate of 720,000 people/year. It is estimated that the number of people with AF will double in most industrialized countries by 2050, with more than half of them aged 80 years and older. Two theories of pathogenesis have been agreed upon – One or more ectopic foci (trigger hypothesis) – Multiple microwave refractions Electrophysiological mechanisms (a) Garrey’s experimental observations and conclusions in the 1920s: There must be a piece of atrial tissue that is essential to the triggering of AF The root of AF is refracture, not autoregulation. Foldback, not autonomic foci, was the root cause of AF Lewis proposed the “foldback” theory 4 years before Garrey, suggesting that AF was triggered by a ring of foldbacks around the suprachiasmatic orifice but the erroneous theory persisted for 35-40 years until the 1950’s Electrophysiologic Mechanisms (ii) Single autonomic foci theory Garrey experimentally disproved the multiple autonomic foci theory Electrophysiologic Mechanisms (III) In the late 1950’s, Moe did a remarkable experimental study and proposed the Multiple Subwave Theory Hint: AF can be triggered by applied electrical stimulation (spontaneous supraventricular tachycardia cannot be triggered by controlled stimulation) Confirmation of AF refractoriness Pathophysiology and Clinical Consequences Three major hazards Ventricular arrhythmias, increased ventricular rate – discomfort Loss of AF Blood transport function, shortened ventricular filling time – impaired hemodynamic function Blood retention in the left atrium – thrombosis Pathophysiology and Clinical Consequences Clinical Classification of AF (3P Approach) Paroxysmal: often sudden onset, self-reversible, usually less than a week in duration, pharmacologically or electrically reversible. Persistent: atrial fibrillation lasting more than 7 days but less than 1 year Permanent: atrial fibrillation lasting more than 1 year Pharmacologic therapy Catheter ablation Surgical therapy Pharmacologic therapy Rhythm control or ventricular rate control Pharmacologic resuscitation in some patients; ventricular rate control to maintain cardiac function Anticoagulation to prevent thrombosis and serious vascular events Occurrence Limitations: only ventricular rate control in most patients, while the greatest risk of atrial fibrillation remains Indications for catheter ablation: paroxysmal atrial fibrillation with frequent, symptomatic episodes that have not responded to medication Limitations: not suitable for chronic and permanent atrial fibrillation High rate of reablation Inaccurate targeting of ablations Widespread ablation affects left atrial function Technological bottlenecks (high skill and experience required of the operator) Surgical treatments began in the early 1980s: corridor procedures Pulmonary venous system (PVS) Early 80’s: corridor surgery pulmonary vein isolation maze surgery I, II, III (invented by Dr. James Cox) Current gold standard is maze III surgery is the only treatment option that can alleviate the 3 aspects of atrial fibrillation that are physiologically abnormal: tachycardia thromboembolism hemodynamic abnormalities Surgical treatment history (i) left atrial isolation (80’s, Williams) Problem: Left atrium still in atrial fibrillation, thrombus may form in left atrium Surgical treatment history (ii) Corridor surgery (Guiraudon, ’85): free the atrial tissue between the sinus node and the AV node, connect the two tissues in a corridor in which atrial fibrillation does not occur Problems: atrial fibrillation still in atrial fibrillation, thrombus may form in left atrium Atrial-ventricular dyssynchrony, impaired hemodynamic function Surgical treatment history (iii) Labyrinth surgery Type I, II (Cox, 89) Maze surgery type III (Cox, 92) Other modified surgery based on maze type III surgery Comparison of the therapeutic effects of the three surgical methods Electrophysiological basis of maze surgery Cox found experimentally that atrial fibrillation is the result of multiple folding loops around anatomical obstruction zones or functional block zones, and that a single folding loop metamorphoses into multiple wavelets, leading Cox to conclude that: atrial fibrillation does not occur in corridor. Cox concluded that the electrophysiologic basis of atrial fibrillation is multiple, sustained large foldback loops. This suggests that the only effective way to prevent refractoriness is to keep the distance between the incisions shorter than the wavelength of the large refractoriness, so that refractoriness cannot form in the gap between the incisions; in addition, sinus impulse and atrial synchronous transmission should be preserved, so that the risk of thromboembolism can be eliminated. Postoperative follow-up revealed two major problems: failure to produce the corresponding sinus tachycardia and left atrial hypoplasia. The Cox Experimental Group found that in humans there is an “an atrial pacemaker complex”, encompassing the sinus node, which is distributed along the right atrium at the junction of the superior vena cava and the terminal crest of the upper and lower chambers, and extends over a wide area of the right atrium. The maze I and II surgeries damaged this complex to varying degrees. The maze III surgery made two improvements on the basis of the maze I and II surgeries: not to make an incision on the top of the right atrium in the maze I type, to avoid damage to the sinus node and its arteries and the sinus impulse generating area of the right atrium and to make a cup shaped incision around the opening of the 4 pulmonary veins, to minimize the size of the maze I and II surgeries, and to make a cup shaped incision in the right atrium. Minimize the extent of the isolated areas of maze types I and II, thereby maintaining left atrial transmission Maze type III surgery (illustrated) Maze type III surgery/targeted maze surgery Injury: blocking the refractory pathway directing conduction from the sinus node to the AV node creates small areas of tissue that are too small to emit electrical impulses Effectiveness of maze type III surgery Risk of stroke with maze surgery Same level as in sinus rhythm (95% mech MVR) Compared to those who did not undergo the maze procedure: the maze procedure significantly reduces the incidence of stroke Compared to those in sinus rhythm: the risk of stroke has been reduced to the same level Maze III: Advantages and Disadvantages Advantages Higher success rate due to permeability: the incision and suture ensures permeable scarring and ensures the blockage of the refractory pathways that cause atrial fibrillation Precise: incision method creates many small areas of tissue that can receive electrical impulses (ensures atrial contractile function) Disadvantages Not widely used because:Unsafe; complex incisions and sutures mean longer operative time, extracorporeal circulation time, and more complications such as bleeding. Not simple and easy to perform; requires a high degree of operating skill Right-side and left-side labyrinthine procedures The right-side and left-side portions of the labyrinthine type III procedure are performed for patients with right atrioventricular and tricuspid malformations and combined simple mitral valve pathology, respectively The surgical results are satisfactory but not as good as those of the labyrinthine type III procedure Surgical procedures versus catheter-based radiofrequency ablation Comparisons of other modifications of the procedure COX-Maze Surgical procedures, despite being effective in the treatment of AF Although COX-Maze surgery is effective in treating AF, it is complicated, time-consuming, and risky, and has been used sparingly. Based on the principles of COX-Maze surgery and the surgical route, various forms of energy ablation surgery have been designed Surgical radiofrequency ablation Surgical radiofrequency ablation Surgical radiofrequency ablation Surgical radiofrequency ablation Surgical radiofrequency ablation of atrial fibrillation is the most widely utilized in clinical practice at the present time, with the Wolf Mini-Maze procedure as the representative. There are several types of radiofrequency ablation catheters, commonly used single-ended ablation and adjustable bipolar probes, pencil-like probes with cold saline infusion at the tip and bipolar clamp-like probes. The probe can be placed on the epicardium under direct vision. Epicardial manipulation can be performed without stopping the heart. The bipolar ablation clamp technique is ideally suited for ablation of the epicardium and allows for timely assessment of permeability, and is an important advance in the surgical treatment of AF Cryoablation applies liquid nitrogen or carbon dioxide gas to the atrial muscle via a probe at a temperature of -60°C for 2 to 3 minutes, producing tissue fibrosis and scarring and blocking electrical excitation conduction. The advantages are that the tissue structure is basically maintained and thrombosis is minimal. Disadvantages freezing is extensive and affects left atrial transmission function. Microwave ablation microwave energy of 40~45W, frequency of 50~60Hz, temperature of 50℃, time of 20~30 seconds, producing atrial muscle burns, the disadvantage is that the clinical application time is relatively short, the effect remains to be observed other ablation energy sources including laser and confocal ultrasound. The biggest characteristic of laser is strong penetration ability, but the shortcoming is that intraoperative damage can not be judged directly, so it is not conducive to the application of surgical direct vision. Confocal ultrasound is similar to laser in terms of damage penetration ability, and its damage range and degree of damage are more controllable, and its damage range can be judged under intraoperative visualization, so it may be a promising new energy source. Modified Saline Flush Radiofrequency Maze Modified Saline Flush Radiofrequency Maze Modified Saline Flush Radiofrequency Maze Modified Saline Flush Radiofrequency Maze Modified Saline Flush Radiofrequency Maze Modified Saline Flush Radiofrequency Maze Modified Saline Flush Radiofrequency Maze Modified Saline Flush Radiofrequency Maze Modified Saline Flush Radiofrequency Maze Maze Maze Maze Maze Maze Maze Maze Maze Maze Maze Maze Maze Maze Maze Maze Maze Maze Maze Maze Maze Maze Maze Maze Maze Maze Maze Mode Step 9 Left Atrial Incision. An incision in the left atrium, the usual one located in the interatrial sulcus, reveals the mitral valve, and the incision line extends upward slightly beyond the inlet at the right upper pulmonary V and downward slightly beyond the left atrial inlet at the right lower pulmonary V. The incision is made in the left atrium, and the incision is made in the left atrium. Modified Saline Flush RF Maze Procedure Modified Saline Flush RF Maze Procedure Modified Saline Flush RF Maze Procedure Modified Saline Flush RF Maze Procedure Modified Saline Flush RF Maze Procedure Modified Saline Flush RF Maze Procedure Maze Procedure Maze Procedure Step 16 Suture Suture closure of the left and right atria. After venting the cardiac chambers, the ascending aortic block clamp is opened. Suture closure of the right atrial incision during the rewarming phase The future of minimally invasive and atrial fibrillation therapy