1. Why do patients have AF?
AF is the abnormal electrical activity of atrium caused by atrial fibrosis resulting from various reasons. Most of the AF occurs in the left atrium due to its anatomical characteristics. In general, the development of AF usually experiences a process from atrial premature contraction, atrial tachycardia, atrial flutter, paroxysmal AF to persistent AF. The rate of progression varies from person to person, some people being decades, while others reaching the stage of persistent AF in a very short time. As long as we live long enough, everyone has the possibility of developing AF. There are numerous diseases associated with the occurrence of AF, including gene mutation, hyperthyroidism, coronary heart disease, hypertension, diabetes, cardiomyopathy, etc. In addition, long-term drinking, overwork, and smoking also serve as the common causes of AF. Generally speaking, the earlier the onset of AF, the greater the correlation with genetic variation. In recent years, the incidence of AF caused by long-term drinking is increasing significantly, but its treatment is rather difficult. In clinic, most AF cannot find a single and specific reason, which will be referred to as idiopathic AF. Sometimes AF will also occur in patients after cardiac surgery. However, those AF episodes are often associated with the operation and may disappear after a period of time.
2. What are the symptoms of AF?
The symptoms of AF vary from person to person. The most common manifestation is palpitation, and patients may also feel chest tightness, shortness of breath or sweating. A few people suffer from polyuria, and they may feel weak for a long time due to the low potassium. The clinical manifestations of AF can be greatly variable. Some people tend to have symptoms in one attack, but the symptoms seem to be unremarkable in the next attack. Moreover, some patients (especially men) are diagnosed with AF by accident in their routine physical examinations or because of other associated diseases. There is a common type of AF called the slow fast syndrome. For those patients, the basic heart rate is usually slow, but it becomes relatively fast when AF occurs. There are also patients whose heart rate is basically normal, but the heart will stop for a few seconds during the conversion from AF to sinus rhythm, causing symptoms of fainting or blackness. There are two atria in our bodies. The right atrium contains a sinoatrial node which is responsible for normal heartbeat. If there is fibrosis in the right atrium, the function of sinoatrial node will be impaired, sinus bradycardia or sinus arrest will occur. While the fibrosis in the left atrium will lead to atrial tachycardia, atrial flutter, AF, etc. Most AF episodes are prone to occur after fatigue, drinking or at night, but the attack mode is generally instable. Patients may think the inducement and regularity of their AF episodes are quite crucial, however, which is not very significant for the treatment.
The most serious harm of AF is causing cerebral infarction, also known as stroke. Some people may also suffer from heart failure symptoms (such as lack of breath, uneven lying, swelling of feet, etc.) due to the fast ventricular rate when AF is ineffectively controlled. Clinically, some patients do not have obvious symptoms, and are diagnosed with AF during physical examinations by accident, which is called asymptomatic AF. To some extent, asymptomatic AF can be more dangerous than symptomatic AF. Because asymptomatic AF may not be treated in time, the possibility of developing stroke or heart failure is relatively higher. Many patients are detected to have AF after cerebral infarction, and some patients become disabled or even die, resulting in great regret and loss.
3. How to diagnose AF?
AF can be easily diagnosed by regular ECGs or ambulatory ECGs, without special examinations. But patients may receive echocardiography, Holter monitoring, and blood tests to rule out other combining diseases. If the attack of AF terminates spontaneously without any treatment, it is called paroxysmal AF. If it cannot be stopped without drugs, or even the drugs are ineffective, it is called persistent AF. If the AF is long-lasting and cannot be converted by drugs or electric cardioversion, it is called permanent AF.
4. How to treat AF?
The treatment of AF is quite difficult and challenging. First of all, we should try drug control. Specific and suitable medical therapy must be made under the guidance of doctors. It is worth noticing that no drug can effectively eradicate AF, except for those caused by hyperthyroidism, Wolff-Parkinson-White syndrome, or cardiac surgery. It is possible that drugs may prevent the attack of AF in some patients, but the lesions of AF will still exist and continue to develop. Therefore, the function of AF medication is only to "maintain stability". Patients with mild symptoms, low risk of stroke, less attack, old age, weak body, serious concomitant diseases or under poor economic conditions may choose drug therapy. However, catheter ablation should be considered if patients are relatively young in age, and have histories of cerebral infarctions in the past, or with high risk of stroke, obvious symptoms, or heart dysfunction.
5. What is radiofrequency catheter ablation or cryoballoon ablation for AF?
Catheter ablation has been widely used for the treatment of AF in the past two decades. Generally speaking, it is a relatively safe and minimally invasive interventional therapy. The major purpose of catheter ablation is to destroy the lesions that may trigger AF by sending catheters into the heart through blood vessel puncture. Unfortunately, however, the efficacy of catheter ablation is somehow unsatisfactory, especially for persistent AF. Evidence has shown that, as for patients with paroxysmal AF, the earlier they receive catheter ablation, the better. After several evolutions, pulmonary vein isolation (PVI) has become the mainstream of catheter ablation for the treatment of AF. However, there have been imperfections in its success rate and long-term recurrence. It has been reported that the 5-year success rate of single ablation for AF is approximately between 15% and 50%. With the progressive development of new AF lesions, the therapeutic range of PVI is comparatively limited. In addition, the current procedure of catheter ablation is difficult to achieve safe and thorough injury. Therefore, the effect of catheter ablation will be improved if the AF patients are recognized earlier, with smaller left atrium and fewer associated diseases. In general, the success rate of catheter ablation for paroxysmal AF can reach about 80% in high-level centers, but the success rate of persistent AF is only around 30-50%.
Our team has originally put forward the linear ablation for AF, the long-term success rate of which is currently in the leading position around the world. Even so, for persistent AF, our past experience shows that only 50% of patients can be completely cured after the one single ablation, while others only achieve improvement. However, with the continuous advances in technology and instruments, our success rate of AF ablation has significantly increased in recent years. The 1-year success rate of paroxysmal AF has exceeded 90%, with persistent AF more than 70%.
The ablation of AF requires highly operational skills, but excessive pursuit of efficacy may lead to risks during procedure, such as heart rupture, stroke and even death. For AF patients with old age, enlarged left atrium and weakness in health, the risk of catheter ablation increases, but the success rate is relatively low. However, if doctors worry too much about the safety of the procedure, the effect of ablation will be reduced inevitably. Some new techniques in ablation (ultrasound ablation, laser ablation, microwave ablation, etc.) have emerged, but they are all eliminated over time. So far, cryoballoon ablation has been performed in a few centers. Since the operational skill of cryoballoon ablation is not very demanding, this technique is quite popular in primary hospitals. However, evidence has shown that its efficacy and safety are not superior to radiofrequency ablation, and may even result in more complications.
In recent years, a new combination of internal and surgical ablation has emerged, which was first implemented by Fuwai Hospital and some other European hospitals. In terms of the so-called combined ablation, the majority of eligible patients usually receive endocardial ablation by puncture of blood vessels at first. After a 3-month observation, if there is no more AF attack, then the ablation is successful, and patients should continue with medication and follow-up. If frequent AF episodes or refractory left atrial flutter/tachycardia are detected during the first 3 months after endocardial ablation, epicardial ablation through thoracoscopy should be considered. The effect of combining endocardial and epicardial ablation is generally better than that of repeated endocardial ablations, and the operative wound is not large. Professor Yao Yan and Professor Zheng Zhe from Fuwai Hospital started to cooperate on the combination of endocardial and epicardial ablation several years ago, and they have achieved good results, with the average success rate of 90%. Of course, if patients have concerns about surgery, they can still choose to undergo another endocardial ablation. It is quite common for AF patients to have multiple ablations. Generally speaking, repeated ablation is comparatively safe and the success rate can be gradually improved. Medical cases of AF patients receiving 5-7 times of ablations have been reported both at home and abroad, which indicates that, on one hand, the proportion of refractory AF is relatively high, on the other hand, the safety of ablation is quite reliable.
It is worth noticing that the cost of AF ablation is relatively high at present, so repeated ablation may be a heavy burden to some patients. But do all AF patients need ablation? In fact, catheter ablation is not necessary for every patient. Due to economic and other reasons, the majority of AF patients are still treated conservatively with drug therapy. The decision whether to pursue and how to conduct catheter ablation should depend on the comprehensive evaluation of patients. It is the doctors’ responsibility to fully inform patients of the advantages and disadvantages of AF ablation. In addition, the doctor should timely judge whether the patient should be operated and if his/her physical or psychological condition can tolerate the procedure.
As for cryoballoon ablation, unlike radiofrequency ablation that destroys lesions of AF by heating, it is achieved by freezing. Since the human body has the ability to maintain constant temperature, it is not easy to cure AF lesions by cryoablation. At present, it seems that the major advantage of this technology is that it’s beneficial for doctors, especially for those with relatively less experience in radiofrequency ablation and catheter operation skills. In addition, patients need to be exposed to a larger dose of radiation and injected with more iodine contrast agent during cryoballoon ablation. Nowadays, cryoablation is only suitable for early-stage paroxysmal AF with mild symptoms, and its efficacy and safety are not better than radiofrequency ablation, with relatively more complications. Cryoballoon ablation is not recommended for patients with persistent AF.
6. Can pacemakers treat AF?
No. The pacemaker is a device that treats bradycardia by monitoring heartbeat and sending the heart electrical signals to beat when heart rate is too slow. In the past, special pacing has been explored to reduce the onset of AF, but that has been proved to be ineffective. The heart rhythm of AF patients is irregular. Since the heart rate of most AF patients is faster than normal, pacemakers are usually not needed. For some patients who only rely on drugs to control AF due to certain reasons, if the heart stops beating for more than a few seconds after taking medicine, pacemakers may need to be implanted in order to maintain the normal heartbeat. However, the decision should be made very carefully, because after withdrawal or adjusting dosage of the drugs, pacemaker implantation may not be necessary. For patients with the slow fast syndrome, there are two treatment options: one is to implant a pacemaker and then take drugs orally to control AF, which is generally suitable for patients with older age, poor physical condition and long medical history of AF; the other is to conduct AF ablation with left atrial autonomic nerve intervention. After this treatment, we have observed that the heart rate of most patients changed from bradycardia to normal, and AF was also cured with very few recurrences. However, it must be noted that AF is not easy to be eradicated. For patients with syncope caused by cardiac arrest after the termination of AF attack, theoretically, it is better for them to receive catheter ablation. Otherwise, pacemakers should be implanted, but they only can prevent syncope not AF.
7. What should patients pay attention to after the ablation of AF?
Ablation of AF is not once and for all. Therefore, patients need to observe patiently for at least 3 months after ablation. AF recurrence in the first 3 months is quite common and often needs drug assistance. The doctor should give patients detailed written instructions before they leave hospital. The decision of whether to receive another ablation will be made 3 months after the procedure. If the recurrence of AF emerges after many years, doctors need to judge whether and when to perform ablation again according to the situation of patients. If the patient has received PVI, he/she should eat soft food in the early 2 weeks after ablation in order to avoid serious esophagus-left atrium fistula, which is mainly manifested as fever, syncope and hemiplegia. Although its incidence is very low, the complication is quite dangerous. Once it occurs, patients should immediately contact the doctor who has performed the ablation. Some patients may feel chest tightness and shortness of breath after ablation, however, majority of patients will relieve in half to one year. The proportion of dyspnea caused by phrenic nerve paralysis after cryoablation is relatively higher, but most of them can recover. Very few patients will have gastroparesis due to the damage of vagus nerve, which is presented with vomiting, unable to eat, requiring timely treatment and drainage.
8. If catheter ablation cannot be performed, what should patients pay attention to the drug therapy?
At present, because of the high cost and the unsatisfactory effect of AF ablation, the vast majority of patients are receiving conservative drug therapy. All the medication should be prescribed according to standard guidelines. Preventing the attack of cerebral infarction is the most important aspect in the management of AF. Doctors should judge the risk scores of cerebral infarction/stroke after comprehensive examinations of patients, so as to decide whether anticoagulant treatment is needed. In addition, patients with tachycardia need to take medicine to control their heart rate, so that their heart function will not be impaired because of the long-lasting fast heartbeat. The heart rate of patients with cardiac insufficiency should not exceed 120 bpm on average. Patients with good cardiac function usually can tolerate the heart rate of more than 120 bpm for several months, but it is still recommended to see a doctor in time and adjust drug dosage or evaluate whether ablation is needed. Warfarin and other anticoagulants should be taken under the guidance of doctors. Recently, the state has approved two new drugs, dabigatran and rivaroxaban, which are comparatively expensive, but do not need repeated blood tests. (from Professor Yao Yan)