Analysis:

Atrial fibrillation is a common arrhythmia, which has become a hot spot in clinical research in recent years. At the same time, it is further recognized that atrial fibrillation is one of the main causes of thromboembolism, and 75% patients in this case are complicated with cerebrovascular accident. Although atrial fibrillation is often accompanied by organic heart disease, about 30% patients have no organic lesions. Patients with atrial fibrillation have symptoms, impaired hemodynamics, disability, shortened life expectancy and increased medical expenses.

Prevention of Thromboembolism in Atrial Fibrillation

Prevention of thromboembolism is one of the important end points of atrial fibrillation treatment, and the risk of embolism is related to the potential heart disease and its nature. Framingham research shows that the risk of thrombosis in atrial fibrillation without rheumatic heart disease is 5.6 times that of the control group, while the risk of thrombosis in atrial fibrillation with rheumatic heart disease is 17.6 times. In recent years, large-scale trials have been conducted in the primary prevention of thromboembolism in atrial fibrillation. The results show that warfarin can reduce the incidence of cerebrovascular accidents from 12% to 4%. Warfarin can increase the risk of bleeding when INR> is at 4 o'clock, and anticoagulation is effective when INR is at 2-3, which does not increase the risk of bleeding. Studies have also shown that warfarin can reduce mortality. Several randomized trials have compared the anticoagulant effects of warfarin and aspirin. Low-dose aspirin (75 mg/day) is not better than placebo, but high-dose aspirin (325 mg/day) is beneficial in atrial fibrillation stroke prevention test.

Transformation of atrial fibrillation

If the drug conversion lasts less than 48 hours, several antiarrhythmic drugs can be used for cardioversion. Since atrial fibrillation is not fatal arrhythmia, any treatment must be safe and have no side effects. 1. A controlled study showed that digoxin was not better than placebo. It has always been thought that cardioversion of atrial fibrillation may be indirectly produced by improving hemodynamic status through its positive inotropic effect, rather than direct electrophysiological effect. 2. An open placebo-controlled study showed that 8 1% of patients with atrial fibrillation could be converted to sinus rhythm by intravenous injection of flecaimide and propafenone. It has been proved that oral fluorouracil and propafenone can be used for conversion and long-term treatment of acute atrial fibrillation. In a placebo-controlled study, a single dose of propafenone (600mg) was given orally, with 50% conversion after 3 hours and 70-80% conversion after 8 hours. Ic drugs are not suitable for patients with heart failure, low ejection fraction and conduction disorder. 3. Recent research shows that oral amiodarone 600mg per day can make 20% patients who fail to switch or use several drugs alternately switch successfully without obvious side effects. Intravenous amiodarone is used to treat acute atrial fibrillation, and the reported effective rate is 25-83%. Commonly used in patients with acute myocardial infarction or Ic drugs. Ibuprofen Park Jung Su is a class III antiarrhythmic drug, which is used to terminate atrial fibrillation by intravenous injection and has been used in the United States. Dove Park Jung Su and Ibrahimovic Park Jung Su are the same kind of drugs, and they also have obvious effects on the termination of atrial fibrillation. It is used for high-risk patients with heart failure, systolic dysfunction and myocardial infarction, and does not affect the mortality rate. The application of class III antiarrhythmic drugs has the potential danger of rapid reversal of ventricular tachycardia. 4. Atrial fibrillation after cardiac surgery is very common, but it is often self-limited. Calcium antagonists and beta blockers have been used in the treatment of postoperative atrial fibrillation, and their effects need to be further confirmed. If atrial fibrillation is secondary to hyperthyroidism, cardioversion should be performed after thyroid function returns to normal.

Electrical cardioversion should be used in time when cardioversion of atrial fibrillation drugs fails or persistent attacks are accompanied by hemodynamic disorders. Transthoracic direct current cardioversion is a method of cardioversion of chronic atrial fibrillation, which can only be successful after one or sometimes multiple electric shocks. Notable technical contents include electrode size, electrode position, transthoracic impedance, output waveform and energy storage (50-400J). It is believed that 75% or more patients with atrial fibrillation can be successfully converted when the initial energy is 200 Joules. If the conversion is unsuccessful at 200 Joules, higher energy (360 Joules) is required. The discharge should be synchronized with proper R wave to avoid ventricular fibrillation induced by electric shock.

For patients with atrial fibrillation lasting for 48 hours or more, oral anticoagulants are recommended 3 weeks before cardioversion and 1 month after cardioversion.

Control of ventricular rate during atrial fibrillation

Drug therapy 1. Digitalis drugs: slow down ventricular rate by delaying atrioventricular conduction and increasing refractory period. At the same time, it also shortens the atrial refractory period to increase atrial rate and increases recessive conduction to slow down ventricular rate. Compared with other drugs, digitalis has unique advantages and can improve patients' heart function. 2. Beta blockers: prolong the effective refractory period and conduction time of atrioventricular node. Intravenous administration can quickly slow down the ventricular rate, but it is not suitable for patients with obvious cardiac insufficiency and organic heart disease, because the muscle strength is negative. Oral drugs can slow down the ventricular rate, so it can obviously improve the exercise tolerance of patients. Even for patients with cardiac insufficiency, oral drugs can improve the quality of life of patients. 3. Calcium antagonists: Verapamil and diltiazem can prolong the refractory period and conduction time of atrioventricular node. Intravenous administration can quickly slow down the ventricular rate, which has a certain negative inotropic effect, but it can be offset by vasodilation. Other drugs such as sotalol and amiodarone can be used to control the ventricular rate of chronic atrial fibrillation. Sotalol itself does not prolong the refractory period of atrioventricular node, and its effect of slowing ventricular rate is related to the blocking effect of β receptor of drugs. Amiodarone can control the ventricular rate of atrial fibrillation at rest and during exercise, and its mechanism is that it can prolong the refractory period of atrioventricular conduction system. Because of its side effects, it is not suitable for long-term use.

Radiofrequency ablation therapy 1. Radiofrequency ablation blocks atrioventricular conduction. 2. Improvement of atrioventricular node.

Use of special equipment

Atrial Pacing Treatment and Prevention of Atrial Fibrillation ① Single point atrial pacing: The location of single point atrial pacing can be near the right atrial appendage, right atrial elevation, right atrial septum, junction and coronary sinus opening. ② Multi-site atrial pacing: it can be divided into double atrial synchronization or right atrial multi-site pacing. On the basis of the original right atrial pacing, the former puts a special coronary sinus lead in the coronary sinus for synchronous pacing of the left and right atria. In the latter, the other electrode is placed under the right atrial septum, boundary X or the opening of coronary sinus. High right atrial pacing can reduce the recurrence rate of atrial fibrillation to 9- 16%, while the recurrence rate of atrial fibrillation in the control group is 32-69%. It is reported that 80% patients can maintain sinus rhythm during multi-site right atrial pacing. At present, it is considered that atrial pacing therapy is a compensatory therapy and an auxiliary means of drug therapy, which cannot replace drug therapy.

Implantable atrial defibrillator is used to treat atrial fibrillation (IAD). One defibrillation electrode with a defibrillation arc is fixed to the atrium in an active manner, while the other defibrillation electrode with a defibrillation arc is fixed to the coronary sinus in a passive manner. Atrial sensing and defibrillation are performed between the right atrium and the coronary sinus electrode. Standard bipolar ventricular electrode leads are used to synchronize ECG and R wave in right ventricular pacing. IAD can record and detect atrial electrogram and electrocardiogram, so as to detect the synchronous perception of atrial fibrillation and R wave. The defibrillator is connected with the lead and implanted in the chest area of the patient in the same way as the ordinary pacemaker. It has been reported that the success rate of IAD to atrial fibrillation is 93.4%, with an average of 1-2 shocks per atrial fibrillation attack, and the electric energy is about 4.6J J. Because of the cost problem, it is rarely used in China at present.

Radiofrequency ablation of atrial fibrillation

Radiofrequency ablation blocks atrioventricular conduction. This technique is to send a large catheter to the position of atrioventricular node and record his beam potential. The discharge energy is 30-50W or 60-70℃ for 60s. Most patients can block atrioventricular conduction 1 time, and then install DDD pacemaker. Whether it is persistent or paroxysmal atrial fibrillation, radiofrequency ablation can bring benefits to patients if drugs are not well controlled: (1) Acute and chronic hemodynamic conditions are obviously improved after radiofrequency ablation. The ejection fraction increased from 27% to 45%, and the probability of heart failure in follow-up patients decreased by more than 50%. (2) The symptoms of palpitation can disappear; (3) Drugs for controlling ventricular rate are no longer needed; (4) Improve the quality of life of patients.

The improvement of atrioventricular node is to change the conduction characteristics of atrioventricular node by radiofrequency ablation, so that the ventricular rate will not be too fast during atrial fibrillation without causing atrioventricular block. The specific method is equivalent to ablation of slow pathway in dual atrioventricular nodal pathways. The Venn point, where the ablation end point was atrial pacing, was advanced to 65438 020 beats/min.

Radiofrequency Ablation of Paroxysmal Atrial Fibrillation 1994 Dr. Haissaguerre of France put forward the concept of focal atrial fibrillation. At present, there is no strict definition, which generally means that atrial fibrillation is triggered or driven by one or more fixed premature beats in the atrium. 70% of this atrial premature beat comes from the left superior pulmonary vein and the right superior pulmonary vein. Followed by left inferior pulmonary vein, right inferior pulmonary vein, right atrial boundary crest, right atrial septum and coronary sinus ostium. In pulmonary veins, pulmonary vein potential (PVP) can be marked from the side to the high point, atrial potential (aP) with low sinus rhythm is in the front and PVP is in the back. In atrial premature beats, the ventricle is early in the front and the atrium is early in the back. During ablation, the PVP potential earlier than P wave was measured on the body surface with a large catheter, and the temperature was set at 60℃ for ablation. At present, because the mechanism and ablation method of atrial fibrillation are still inconclusive, the ablation success rate is only 30%, and the recurrence rate and complications are high, which is only in the exploration stage. From June, 5438 to October, 2000 10, Haissaguerre put forward the latest theory again, and used PV ring-shaped mapping electrode to map and ablate the part with the earliest bidirectional conduction at the opening of pulmonary vein, thus blocking the conduction path between atrium and pulmonary vein and significantly shortening the operation time. The success rate of single ablation was 56%(39/70) and the total success rate was 72% (5/kloc-). The renewal of theory and the improvement of instruments bring new hope for radiofrequency ablation of atrial fibrillation.