Prevention of thromboembolism in atrial fibrillation
Prevention of thromboembolism is one of the most important endpoints in the treatment of atrial fibrillation, and the risk of embolism is related to the nature and nature of the underlying heart disease.In the Framingham study, the risk of thrombosis in atrial fibrillation with nonrheumatic heart disease was 5.6 times greater than in the control group, and the risk of thrombosis in atrial fibrillation with wind disease was 17.6 times greater. Recent large-scale trials in primary prevention of thromboembolic events in atrial fibrillation have shown that warfarin reduces the incidence of cerebrovascular accidents from 12% to 4%. Warfarin increases the risk of bleeding when the INR is 4. Anticoagulation is effective when the INR is 2-3 and does not increase the risk of bleeding, and studies have shown that warfarin reduces mortality. There have been several randomized trials comparing warfarin to aspirin for anticoagulation. Small doses (75 mg/day) of aspirin were no better than placebo, whereas larger doses (325 mg/day) of aspirin were beneficial in the Atrial Fibrillation Stroke Prevention Trial.
Revolution of Atrial Fibrillation
Drug Revision Several antiarrhythmic drugs can be used to revive recent atrial fibrillation that has lasted less than 48 hours. Because atrial fibrillation is not a fatal rhythm disorder, any treatment must be safe and free of side effects. 1. Controlled studies have shown that digoxin is no better than placebo, and that it has been consistently implicated as contributing to atrial fibrillation resuscitation, probably indirectly through its positive inotropic effect on hemodynamics, rather than its direct electrophysiologic effect. 2. Open and placebo-controlled studies have shown that intravenous fluticasamine, cardioplegia, and cardioplegia can reset atrial fibrillation in 81% of patients. 3. Open and placebo-controlled studies have shown that intravenous flecainide and cardioplegia can convert atrial fibrillation to sinus rhythm in 81% of patients. Oral flutamide and cardioplegia have been demonstrated to be useful in the recovery of acute atrial fibrillation and in the long-term treatment of atrial fibrillation. In placebo-controlled studies, a single oral loading dose of 600 mg of cardioplegia resulted in 50% reversal of rhythm after 3 hours and 70-80% return to rhythm after 8 hours. Class Ic drugs should not be used in patients with heart failure, low ejection fraction, and conduction disorders.3. Recent studies have shown that daily oral amiodarone 600mg can result in successful resuscitation in 20% of patients who have failed resuscitation or who have alternated between several medications, with no significant side effects. Intravenous amiodarone is used in the treatment of acute atrial fibrillation, with reported efficacy rates of 25-83%, and is commonly used in patients with acute infarction or class Ic counterindications.Ibutilide, a class III antiarrhythmic drug used to terminate atrial fibrillation intravenously, has gained access to use in the U.S. The use of dofetilide with Ibutilide has also been shown to increase the effectiveness of atrial fibrillation. Dofetilide is in the same class as Ibutilide and is also effective in terminating atrial fibrillation, and is used in patients with heart failure, hyposystole, and high post-infarction risk without affecting mortality. There is a potential risk of tip-twisting ventricular tachycardia with the use of class III antiarrhythmic drugs.4 Complications of atrial fibrillation after cardiac surgery are common, but have a self-limiting tendency. Calcium antagonists and beta-blockers have been used in the treatment of post-surgical atrial fibrillation, and their efficacy needs to be further confirmed. If atrial fibrillation is secondary to hyperthyroidism, transrhythmia should be performed after normalization of thyroid function.
Electrical resuscitation When atrial fibrillation drug resuscitation fails or persistent episodes with hemodynamic disorders, electrical resuscitation should be used. Transthoracic extracorporeal direct current resuscitation is a method of chronic atrial fibrillation transrhythmia, a single or sometimes several shocks before success. Technical aspects of note include electrode size, electrode position, transthoracic impedance, output waveform, and energy storage (50-400 J). A starting energy of 200 J is advocated for successful AF reversal in 75% or more of patients, with higher energies (360 J) required if 200 J reversal is unsuccessful. The discharge needs to be synchronized with the appropriate R wave, which avoids shock-induced ventricular fibrillation.
Oral anticoagulant therapy is advocated 3 weeks before and 1 month after reversal in patients with atrial fibrillation lasting 48 hours or longer.
Control of ventricular rate in atrial fibrillation
Drug therapy 1. Digitalis drugs: slow down the ventricular rate by slowing down atrial conduction and increasing the period of refractory period. At the same time, it also shortens the atrial refractory period to increase the atrial rate, and increases the occult conduction to slow down the ventricular rate. Digitalis has a unique advantage over other drugs in that it improves cardiac function in patients.2. Beta blockers: Prolongs the effective atrioventricular node oprtation and conduction time. Intravenous administration rapidly slows the ventricular rate, but is not indicated in patients with significant cardiac insufficiency and organic heart disease due to negative inotropic effects. Oral administration can slow the ventricular rate, so it can significantly improve the patient's exercise tolerance, even in patients with cardiac insufficiency, oral administration can improve the patient's quality of life.3. Calcium antagonists: verapamil and diltiazem can prolong the atrioventricular node's duration of refractory period and conduction time. Intravenous administration slows the ventricular rate rapidly and has some negative inotropic effect but can be counteracted by vasodilatory effects. Other drugs such as sotalol and amiodarone can be used to control ventricular rate in chronic AF. Sotalol itself does not prolong the AV nodal oprtension, and its ventricular rate-slowing effect is related to the beta-blocking effect of the drug. Amiodarone controls the ventricular rate in atrial fibrillation at rest and during exercise by a mechanism that prolongs the atrioventricular conduction system's occlusion period, and it should not be administered for long periods of time because of side effect limitations.
Radiofrequency ablation therapies 1. Radiofrequency ablation to block atrioventricular conduction. 2. Atrioventricular node modification.
Use of special devices
Atrial pacing for the treatment and prevention of atrial fibrillation ①Single-site atrial pacing: single-site atrial pacing can be located in the right auricle, the elevated right atrium, the right interatrial septum, the boundary and, near the opening of the coronary sinus. Multi-site atrial pacing: there are two types of pacing: bi-atrial synchronization or multi-site pacing in the right atrium. In the former, on the basis of the original right atrial pacing, a special coronary sinus lead is placed in the coronary sinus for synchronized left and right atrial pacing. The latter places another electrode below the right septum, border X, or coronary sinus opening. High right atrial pacing reduced the recurrence rate of AF to 9-16% compared with 32-69% for control VVI pacing. With right atrial multisite pacing, sinus rhythm has been reported to be maintained in 80% of patients. Atrial pacing therapy is currently considered to be compensatory therapy, an adjunct to, and not an alternative to, pharmacologic therapy.
Implantable atrial defibrillators (IAD) are used to treat atrial fibrillation (AF) with one defibrillation electrode with a defibrillation arc secured to the atria in an active manner and another defibrillation electrode with a defibrillation arc secured to the coronary sinus in a passive manner. Atrial sensing and defibrillation were performed between the right atrial and coronary sinus electrodes. A standard bipolar ventricular electrode lead is used for intracardiac electrogram R-wave synchronization and right ventricular pacing.The IAD records and detects intra-atrial electrograms and electrocardiograms for detection of atrial fibrillation and R-wave synchronization perception. The defibrillator is implanted in the anterior chest area of the patient with leads attached in the same way as a regular pacemaker. The success rate of IAD in reversing atrial fibrillation has been reported to be 93.4%, with an average of 1-2 shocks per episode of atrial fibrillation, and an electrical energy of about 4.6 J. Because of the cost problem, there are few applications in China at present.
Radiofrequency ablation for atrial fibrillation
Radiofrequency ablation to block atrial conduction The technique is to send a large catheter to the AV node to record the Hippocratic potential, the discharge energy is 30-50W or 60-70 ℃ for 60s, and most of the patients can be able to block atrial conduction in one time, and then install a DDD pacemaker. In both persistent and paroxysmal atrial fibrillation that is not well controlled medically, radiofrequency ablation blockade of the AV conduction system can be beneficial: (1) The hemodynamic status was significantly improved after radiofrequency ablation in both acute and chronic cases. Ejection fraction increases from 27% to 45%, and the chance of heart failure episodes is reduced by more than 50% in patients at follow-up; (2) patients' palpitations may disappear; (3) medications to control ventricular rate are no longer needed; and (4) patients' quality of life is improved.
Atrioventricular node modification Atrioventricular node modification is a radiofrequency ablation method that changes the conduction characteristics of the AV node so that the ventricular rate is not too fast during atrial fibrillation without causing complete atrioventricular block. This is equivalent to ablating the slow path of the AV node dual pathway. The ablation endpoint is the advancement of the atrial pacing Venn diagram to 120 beats/min.
Radiofrequency ablation for paroxysmal atrial fibrillation The concept of focal atrial fibrillation was introduced by Dr. Haissaguerre in France in 1994. There is no strict definition, but it generally refers to atrial fibrillation triggered or driven by one or more fixed occurrences of atrial premature beats in the atria. Seventy percent of such atrial premature beats originate from the left upper pulmonary vein and the right upper pulmonary vein. This is followed by the left inferior pulmonary vein, the right inferior pulmonary vein, the right atrial border ridge, the right interatrial septum, and the vicinity of the coronary sinus orifice, respectively. A high apical pulmonary vein potential (PVP) can be lateralized within the pulmonary veins, and a low, blunt atrial potential (aP) is anterior and posterior to the PVP in sinus rhythm; the PVP is anterior and posterior to the aP in atrial premature. Ablation was performed with a large head catheter labeled to the PVP potential that was most advanced compared with the surface P wave, and the temperature was set at 60°C for ablation. At present, because the mechanism of AF and the ablation method are still inconclusive, the success rate of ablation is only 30%, and the recurrence rate and complications are high, so it is only in the exploratory stage.In November 2000, Haissaguerre put forward the newest theory again, the use of PV ring-shaped marking electrodes to mark the earliest two-way conduction at the opening of the pulmonary veins for ablation, so as to block the conduction path between the atrium and the pulmonary veins, and significantly shorten the procedure time. This has resulted in a significant reduction of the procedure time, with a success rate of 56% (39/70) for a single ablation and 72% (51/70) for the total procedure. In addition, the creation of the ultrasound balloon catheter easily blocked the conduction between the atria and the pulmonary veins. Updated theories and improved devices have shown new promise for radiofrequency ablation for atrial fibrillation.