1.The normal rhythm of the heart
The excitation of the normal heart starts from the sinus node, which has automatic rhythm and emits neatly rhythmic excitation (60~100 times/minute), and then the excitation is transmitted to the ventricles through the atria and atrioventricular node in turn, so that the whole heart contracts and diastole in a regular and coordinated sequence, thus ensuring the pumping function of the heart, which is called sinus rhythm (Figure 1).
Figure 1 Normal sinus rhythm
2.The concept of atrial fibrillation
Atrial fibrillation is a supraventricular arrhythmia characterized by rapid and disordered electrical activity in the atria, where the atrial muscle exhibits irregular fibrillation, resulting in the loss of normal contraction and diastole function. On the electrocardiogram, atrial fibrillation is characterized by the replacement of normal P waves by fast oscillatory waves or fibrillation waves of varying size, shape, and duration (Figure 2).
Figure 2 shows normal sinus rhythm on the left and atrial fibrillation on the right, with multiple irregular electrical activities in the atria.
3. Prevalence of atrial fibrillation in the population
Atrial fibrillation is the most common clinical arrhythmia, accounting for about 1/3 of the patients hospitalized with arrhythmia. foreign epidemiological study (Framingham study) reported that the population prevalence is 0.5%, and the prevalence increases with age; the prevalence can rise to 6% in people over 60 years old, while the prevalence in people over 80 years old is as high as 8.8%. A study done in 2003 by Professor Hu Dayi and others in China showed that the total prevalence in China was 0.77%, and that the number of patients with atrial fibrillation in China was conservatively estimated to be at least 8 million, while the number of patients with atrial fibrillation in Europe was about 4.5 million and the number of patients in the United States was about 2.2 million, so the number of patients with atrial fibrillation in China has exceeded the total number of patients in Europe and the United States. Almost silently, China has become the number one country with atrial fibrillation (Figure 3).
Figure 3 Comparison of the prevalence of atrial fibrillation in China, the United States, and Europe
4. Common causes and triggers of atrial fibrillation
Acute causes of atrial fibrillation include alcohol consumption, electric shock, surgery, myocarditis, acute myocardial infarction, pericarditis, acute pulmonary embolism, and electrolyte disorders, etc. Most of the acute causes of atrial fibrillation can improve or stop after removing the causes.
Chronic cardiovascular diseases such as hypertension, coronary heart disease, heart valve disease (such as mitral stenosis or insufficiency), chronic heart failure, cardiomyopathy (such as hypertrophic cardiomyopathy), chronic pulmonary heart disease (COPD), etc. can lead to persistent atrial fibrillation.
5, the clinical manifestations of atrial fibrillation and long-term harm
The clinical manifestations of atrial fibrillation are diverse, with palpitations, shortness of breath after activity, or even no symptoms in mild cases, while vertigo, chest tightness, dyspnea, or even black haze and syncope may occur in severe cases.
The main distant hazards of atrial fibrillation are.
(1) Cerebral embolism: Cerebral embolism is the complication with the highest disability rate in patients with atrial fibrillation, mostly due to cerebral artery embolism caused by dislodged thrombus in the left atrium, and the risk of cerebral embolism is higher if atrial fibrillation is accompanied by rheumatic heart valve disease or prosthetic valve replacement. Atrial fibrillation is currently responsible for about 1 in 6 strokes.
(2) Heart failure: Heart failure and atrial fibrillation are mutually exclusive. Patients with heart failure have an increased chance of developing atrial fibrillation, while atrial fibrillation can further worsen heart failure. Atrial fibrillation can greatly increase mortality in patients with heart failure, and one study showed that atrial fibrillation can increase the risk of death in patients with heart failure by 52% over 4 years (Figure 4).
(3) Aggravating myocardial ischemia. With the continuous development of China’s economic level, people’s dietary structure and lifestyle have changed dramatically, leading to a significant increase in the incidence of coronary heart disease, and atrial fibrillation, especially rapid atrial fibrillation, can further aggravate myocardial ischemia in patients with coronary heart disease, which is a more than 1-fold increase in the risk of death in patients with coronary heart disease.
Figure 4 Survival rate of patients with atrial fibrillation compared with the total population (■ represents patients with atrial fibrillation; ▲ represents the total population. (The horizontal axis is the follow-up time, and the vertical axis is the survival rate.)
6. Treatment objectives of atrial fibrillation
1) Conversion of atrial fibrillation rhythm to restore and maintain sinus rhythm in the long term is the preferred curative measure (Figure 5).
(2) To control the rapid ventricular rate during atrial fibrillation episodes and improve the patient’s quality of life, which is the symptomatic treatment of palliation.
3) Prevention of thromboembolic or stroke complications of atrial fibrillation is a hopelessly anti-consequential measure.
Figure 5: The preferred treatment for atrial fibrillation: to revert the rhythm of atrial fibrillation to restore and maintain sinus rhythm for a long time
7, the treatment of atrial fibrillation
(1) Etiological treatment
In a few cases, the etiology of atrial fibrillation is relatively clear, for example, it is known that hyperthyroidism, acute moderate alcohol, drugs and stress can cause atrial fibrillation. In such cases, the etiology of atrial fibrillation should be treated first. However, it should be noted that after effective elimination or control of the causative agent or coexisting diseases, AF may disappear on its own in some patients; however, in most cases, AF will continue to attack.
2) Drug treatment
(1) Prevention of thromboembolism: Anticoagulation therapy with warfarin is mainly used for elderly patients, combined valve disease, post-prosthetic valve replacement, and diabetic patients to prevent thromboembolism, especially cerebral embolism.
Ventricular rate control: For elderly patients, patients who cannot tolerate radiofrequency ablation and patients with chronic atrial fibrillation who have failed to perform atrial fibrillation, consider using digitalis, beta-blockers and calcium antagonists (e.g., Hershey’s) to control the ventricular rate in atrial fibrillation, usually between 80 and 90 beats/min in atrial fibrillation at rest and around 110 beats/min in mild activity. The ventricular rate at rest is usually between 80 and 90 beats/min, and the ventricular rate at light activity is around 110 beats/min.
③Reversion of atrial fibrillation and maintenance of sinus rhythm: these drugs mainly include amiodarone, dronedarone, sotalol, propafenone and morethizine, etc. Most of the drugs to revert sinus rhythm need to be taken for a long time to maintain sinus rhythm, but most of these drugs have obvious side effects or even increase mortality in patients with cardiac insufficiency, and the success rate of maintaining sinus rhythm is less than 50%, which is mostly effective at the beginning of use and decreases with the prolongation of use. With the prolongation of the use of time, the effectiveness of the drug decreases or fails. Among them, the common clinical use of cortolone can cause abnormal thyroid function (hypothyroidism or hyperthyroidism), long-term high dose can cause pulmonary fibrosis liver function damage, corneal pigmentation, photosensitivity and other side effects.
Upstream treatment to prevent new-onset AF or recurrence of AF: It mainly refers to the application of angiotensin-converting enzyme inhibitors (ACEI) or angiotensin receptor antagonists (ARB), beta-blockers and statins to patients with common underlying diseases of AF, such as hypertension, coronary heart failure and hypercholesterolemia, thus helping to prevent new-onset AF or recurrence of AF in patients with such underlying diseases.
3) Catheter ablation
(1) Mechanism of radiofrequency ablation of atrial fibrillation: It is currently believed that the mechanism of occurrence and maintenance of atrial fibrillation is the focal origin (★) often located in the pulmonary vein region, its presence of fibrillation-like conduction, and foldback excitation, i.e., simultaneous foldback of multiple subwaves (Figure 6A, B).
Figure 6 Mechanism of atrial fibrillation
Based on the above theory, catheter radiofrequency ablation is performed by delivering a cardiac catheter into the atrium through a peripheral vein and distributing high-frequency electrical waves at the site where the left atrium joins the pulmonary vein. The radiofrequency energy generates heat to increase the temperature of the tissue in contact with the head end of the catheter that distributes the radiofrequency current, and protein denaturation and necrosis. The ablation is performed along the opening of the pulmonary vein for one week, forming a circular scar (Figure 7), thus isolating the folding of the pulmonary vein to the left atrium or restricting the abnormal excitation that causes atrial fibrillation to the pulmonary vein so that it cannot be transmitted to the atrium, thus achieving the goal of eradicating atrial fibrillation. In patients with persistent atrial fibrillation, in addition to ablation around the pulmonary veins, continuous linear ablation in other parts of the atrium is required. This is known as atrial fibrillation catheter radiofrequency ablation.
An example is a case of a 64 male with paroxysmal atrial fibrillation for 7 years, who was taking intermittent cardioplegia and cortolone and still had recurrent episodes of atrial fibrillation. This is shown in Figure 8. After admission, ablation of the pulmonary veins and left atrium was performed in the catheterization laboratory via the CARTO 3D scaler system (Figure 9), and sinus rhythm was restored after the procedure (Figure 10).
Figure 8 Electrocardiogram showing atrial fibrillation on admission
Figure 9 From left to right, the three-dimensional images of atrium and pulmonary vein in anterior, left anterior oblique, and right anterior oblique positions created by CARTO 3-D scaler system, with red dots as ablation points and electrical isolation of pulmonary veins.
Figure 10 Patient recovered sinus rhythm after radiofrequency ablation
②The success rate and risk of atrial fibrillation catheter ablation: About 70% of paroxysmal atrial fibrillation and 60% of persistent atrial fibrillation can return to normal sinus rhythm 3 months after a single ablation, and the success rate of paroxysmal atrial fibrillation ablation can reach 90% after the second or third ablation. Persistent AF can also reach 80%. This success means that the patient is able to maintain a stable sinus rhythm without the need for any antiarrhythmic drugs. In other patients, the frequency of AF episodes may be significantly reduced after the procedure, or the absence of episodes may be maintained with antiarrhythmic drugs. Risks of catheter ablation: Because it has become a routine clinical treatment for atrial fibrillation, transcatheter radiofrequency ablation for atrial fibrillation is generally safe, with an incidence of serious complications usually <1%. However, as with some other invasive procedures, there are some risks associated with this treatment. The risks associated with the procedure will be carefully explained to you before the procedure. During the procedure, the surgeon will do his best to be responsible and take some precautions to minimize the risks of the procedure.
Patients who are suitable for radiofrequency ablation for atrial fibrillation.
Patients with frequent episodes of paroxysmal atrial fibrillation or persistent atrial fibrillation with significant symptoms.
Patients with atrial fibrillation for whom drug therapy has failed or who do not want to take drugs.
Patients who cannot tolerate antiarrhythmic drugs, or who experience serious side effects after medication.
Patients with coexisting serious cardiac disorders such as heart failure, sometimes requiring treatment of the coexisting disorders first so that the patient can tolerate the radiofrequency ablation procedure
Patients who have had a permanent pacemaker, an implantable cardioverter-defibrillator (ICD), or a prosthetic heart valve replacement for rheumatic heart disease may also receive this treatment.
Age >80 years is subject to the patient’s general condition.
4) Other considerations for patients with atrial fibrillation
Patients with atrial fibrillation should quit smoking, limit alcohol consumption, eat a low-salt, low-fat diet, and control their weight. Some patients may need to avoid caffeine-containing substances such as tea, coffee, and cola. Some patients may need to avoid caffeine-containing substances such as tea, coffee, cola, etc. Exercise moderately and actively treat a number of diseases associated with the disease, including hypertension and diabetes. Apply caution when taking some over-the-counter medications. Certain medications for colds may contain stimulants that can cause irregular heart rhythms, and you should ask your doctor or read the instructions before taking them to see if they are right for you.
Patients taking drugs such as warfarin and cortolone or after radiofrequency ablation should be followed up regularly on an outpatient basis with regular review of coagulation function (e.g. INR), electrocardiogram, ambulatory electrocardiogram (Holter) and echocardiogram.