I. Epidemiology and classification of atrial fibrillation.
Atrial fibrillation (atrial fibrillation for short), is one of the most common arrhythmia diseases. During an episode of atrial fibrillation, various parts of the atria present a rapid and disordered flutter, up to about 500 times per minute. As the atria are unable to perform normal and regular contraction and diastole activities, the ventricular beating also becomes uneven, with the heart rate reaching 130-160 beats per minute when it is fast and 50 beats per minute when it is slow, which is extremely irregular.
According to epidemiological surveys, there are nearly 9 million patients with atrial fibrillation in China, and the trend is increasing year by year. What is more noteworthy is that the incidence of atrial fibrillation increases with age, with a prevalence of up to 5.9% in people over 65 years of age, and even up to 10% in people over 75 years of age.
According to the latest research atrial fibrillation confirmed that atrial fibrillation can lead to a significant increase in arterial embolism in the brain and limbs, leading to heart failure, reduced quality of life and increased mortality in patients. Atrial fibrillation has become a serious health problem that endangers people’s health in the 21st century.
According to the duration and characteristics of atrial fibrillation episodes, the “3P” classification method was often used in clinical practice, namely.
① Paroxysmal atrial fibrillation (Paroxysmal atrial fibrillation);
② Persistent atrial fibrillation (Persistent atrial fibrillation);
③Pemanent atrial fibrillation.
The latest ESC 2010 guidelines for the treatment of atrial fibrillation classify atrial fibrillation into five categories: first diagnosed atrial fibrillation, paroxysmal atrial fibrillation, persistent atrial fibrillation, long-standing persistent atrial fibrillation (atrial fibrillation lasting longer than 1 year) and permanent atrial fibrillation. The common causes of atrial fibrillation are hypertension, valvular disease, coronary artery disease, precordial disease, hyperthyroidism, etc. Some patients with atrial fibrillation cannot find a clear cause clinically generally diagnosed as isolated atrial fibrillation and idiopathic atrial fibrillation The former refers to patients who are relatively young, under 55 years of age, while the latter refers to patients over 55 years of age, whose age increases, the risk of organic organ disease also increases.
Second, the pathogenesis of atrial fibrillation.
The pathogenesis of atrial fibrillation includes the focal excitation and foldback theory, and it is currently believed that atrial fibrillation often arises as a result of the action of multiple factors. Atrial enlargement, slow conduction, shortened atrial expiration, and increased dispersion can all contribute to the occurrence of atrial fibrillation. Although various theories cannot be fully unified, it is undeniable that the generation of atrial fibrillation requires triggering factors and the maintenance of atrial fibrillation requires corresponding substrates, and other factors such as inflammation and autonomic nerves can also synergistically promote the triggering and maintenance of atrial fibrillation.
Third, the treatment strategy of atrial fibrillation.
1. The traditional therapeutic goals of atrial fibrillation include.
① control of ventricular rate ;
(2) Conversion of sinus rhythm;
③Maintain sinus rhythm to prevent recurrence;
④ Prevention and control of thromboembolic complications.
For the first time, the ESC 2010 guidelines for the treatment of atrial fibrillation include “hospitalization” along with “death and stroke” in the top three goals for the treatment of atrial fibrillation. The ESC 2010 Atrial Fibrillation Treatment Guidelines for the first time include “hospitalization” among the top three goals of atrial fibrillation treatment, along with “death” and “stroke. The aim of atrial fibrillation treatment is to relieve symptoms, reduce hospitalization, reduce cardiovascular events, and improve survival.
2, The treatment strategy of atrial fibrillation mainly includes the following aspects.
(1) Rhythm control: pharmacological resuscitation and maintenance of sinus rhythm: rhythm control strategies are usually used mainly to relieve symptoms associated with atrial fibrillation, while those without significant symptoms (or those without symptoms after heart rate control therapy) usually do not need to receive antiarrhythmic drugs. Commonly used antiarrhythmic drugs include amiodarone, dronedarone, flecainide, propafenone, and sotalol. The ESC 2010 guidelines for the treatment of atrial fibrillation place greater emphasis on the use of dronedarone as a first-line drug instead of amiodarone.
(2) Heart rate control: Previous guidelines recommended a strict heart rate control strategy of 60-80 beats/min at rest and 90-115 beats/min during moderate physical activity. The ESC 2010 guidelines for the treatment of atrial fibrillation recommend that a relaxed heart rate control strategy is reasonable for those without severe tachycardia-related symptoms; for patients with a strict ventricular rate control strategy, an exercise test and 24-h ambulatory electrocardiogram are required for safety reasons if the heart rate is too fast during physical activity.
Drug choices include β-blockers, non-dihydropyridine calcium antagonists and digoxin; if the above drugs are not effective, amiodarone can also be used to control the ventricular rate of atrial fibrillation; in addition, dronedarone can effectively slow down the heart rate at rest or during activity, and can be applied to the heart rate control of recurrent paroxysmal atrial fibrillation.
(3) Antithrombotic therapy: the commonly used antithrombotic drugs are aspirin and warfarin. The choice of antithrombotic regimen for patients with atrial fibrillation should be based on risk factor stratification of patients with atrial fibrillation and control of INR to 2-3. ESC2010 guidelines for the treatment of atrial fibrillation recommend that
①All patients with atrial fibrillation should be treated with antithrombotic therapy, except for low-risk patients or those with contraindications.
Patients with no risk factors (isolated AF without any risk factors) may be treated without antithrombotic therapy.
(③For those who refuse to take oral anticoagulants or have contraindications, aspirin (75-100 mg) and clopidogrel (75 mg) can be substituted in combination.
(iv) Patients with atrial fibrillation should be assessed for bleeding risk before starting antithrombotic therapy. Caution should be exercised for those at high risk of bleeding whether they receive warfarin or aspirin.
IV. Radiofrequency ablation of atrial fibrillation
Catheter radiofrequency ablation for atrial fibrillation is one of the most popular hot spots in clinical cardiac electrophysiology in the past 10 years. After continuous exploration, encouraging progress has been made in recent years, and some large cardiac electrophysiology centers in China have become very mature, and the success rate of radiofrequency ablation of paroxysmal atrial fibrillation can reach more than 80% or even 90%. 1998, French doctors such as Haissaguerre confirmed the role of abnormal electrical activity in the pulmonary veins in the triggering mechanism of atrial fibrillation, and applied catheter ablation to treat atrial fibrillation. In 1998, Haissaguerre and other French physicians demonstrated the role of abnormal electrical activity in the pulmonary veins as a trigger mechanism for atrial fibrillation and successfully applied catheter ablation therapy, creating a milestone in atrial fibrillation ablation and establishing the basic approach with pulmonary vein isolation as the cornerstone.
The development of the CRRTO three-dimensional calibration navigation system has made RF ablation of atrial fibrillation as if it were a direct cardiac operation, making RF ablation of atrial fibrillation safer, significantly shortening the operation time and improving the success rate, and promoting the further development of RF ablation of atrial fibrillation.
1, on catheter ablation of atrial fibrillation – 2008 Chinese expert consensus on the indications for radiofrequency ablation of atrial fibrillation proposed in.
(1) Paroxysmal atrial fibrillation: Symptoms are obvious, especially in young people – catheter ablation is the first-line treatment to improve symptoms, quality of life and social activity;
(2) Persistent atrial fibrillation: <3 years (especially <1 year); ineffective or intolerant to class I or III antiarrhythmic drug therapy; frequent episodes of symptomatic atrial fibrillation; no organic heart disease - catheter ablation as the treatment of choice.
(3) Patients with long medical history, combined with organic heart disease (including strictly selected patients with symptomatic heart failure) and elderly patients with atrial fibrillation – catheter ablation can be used as one of the measures to maintain sinus rhythm and prevent recurrence. The contraindications to catheter ablation are few, and only left atrial/left ear thrombus is an absolute contraindication.
2.The principle of catheter radiofrequency ablation
Studies have shown that at least about 95% of atrial fibrillation and pulmonary veins are closely related. Normally, there are four pulmonary veins in humans that converge from the back of the heart into the left atrium. Catheter ablation is usually performed through the femoral vein of the lower extremity by first performing two atrial septal punctures and delivering the SWARZS sheath, but not the PREFAECE sheath, into the left atrium so that the catheter can enter the left atrium from the right atrium. High-frequency electromagnetic waves, or radiofrequency energy, are delivered at the site where the left atrium is connected to the pulmonary vein, and ablated for one week along the opening of the pulmonary vein. The radiofrequency energy passively heats the surrounding tissue, raising the tissue temperature and forming a circular scar that confines the abnormal excitation that causes atrial fibrillation to the pulmonary vein so that it cannot be transmitted externally, thus achieving the goal of eradicating atrial fibrillation.
In rare cases, some other sites within the heart (e.g., the superior vena cava) can also give off abnormal impulses, when these sites also need to be isolated. Due to the small diameter of the cardiac catheter and the fact that the head end of the special catheter always has six small holes to flush the ablation sites with saline to avoid excessive temperatures, this not only facilitates the release of more energy to ensure complete coagulation necrosis of a very small portion of myocardial tissue, but also reduces the extent of the damage.
While the catheter is abutting the myocardium, the advanced CARTO electrophysiological 3D scaler system uses the GPS magnetic field navigation principle to record the trajectory of the catheter in real time and construct a model of the left atrium. It is then precisely fused with the patient’s CT images and ablated as if it were open-heart surgery with the mutual evidence of X-ray images. The ablation sites are memorized using this calibration system to ensure that there are no missed sites and complete isolation during the ablation process. Further ablation strategies will be adopted for persistent atrial fibrillation, atrial fibrillation caused by impulses issued from other sites, and atrial flutter occurring after atrial fibrillation isolation, such as increasing the top ablation line, fragmentation potential, ablation of specific focal points, and ablation of the atrial isthmus.