Pre-excitation” means that in addition to the normal conduction pathway (atrioventricular node), there is one or more abnormal electrical conduction pathways (also known as bypass) between the atria and the ventricles, and the presence or absence of “pre-excitation” can usually be clarified by a simple general ECG. The presence or absence of “pre-excitation” can usually be determined by a simple general ECG. In the general population, about 0.1 to 0.3% of people have “pre-excitation”. Some patients with “pre-excitation” are asymptomatic and are only detected by physical examination, while most patients with “pre-excitation” are usually confirmed by electrocardiography after the onset of tachycardia. “The most common and typical of these tachycardias is paroxysmal supraventricular tachycardia (usually not fatal, but recurrent and increasing in frequency and duration with age), for which the clinical consensus is choose catheter ablation to treat them. There is also a small percentage of patients with pre-excitation whose tachycardia is not typical supraventricular tachycardia, but atrial fibrillation, atrial flutter and other arrhythmias, which are eventually confirmed by electrocardiogram; for most of these patients catheter ablation is still preferred for treatment, but a comprehensive evaluation is needed, and some patients can be treated surgically for pre-excitation only, while others need further interventions for atrial flutter and atrial fibrillation. Does pre-excitation require surgery or not? For patients with tachycardia, the indications for surgery are clear and generally acceptable to most patients, and there is no question. For those patients with tachycardia who are not tachycardic (i.e., asymptomatic preexcited patients), there are different opinions. Many physicians in the past (including today) believe that asymptomatic (tachycardic) preexcitation is benign and does not require further intervention. But this is a very wrong view. The first thing that needs to be clarified is that asymptomatic pre-excitation is most likely only a state of a certain stage, because most patients with previously asymptomatic pre-excitation may later develop tachycardia or other symptoms, such as heart enlargement and heart failure, as they age. In recent years, the medical community has become increasingly concerned about this issue, because in many cases, it is only after the development of very serious complications that they are taken seriously, and after the removal of the “asymptomatic” preexcitation bypass, the complications are corrected and even reversed in many patients. What is the current progress of the study? A prospective follow-up study published in 2012 in Circulation, a leading international cardiovascular journal, found that patients with a single episode of tachycardia (without catheter ablation) had a 7% incidence of malignant arrhythmic events and a 1.4% incidence of hemodynamic disturbances and cardiac arrest over a 5-year follow-up period. In patients with asymptomatic preexcitation, as in those with symptomatic preexcitation, features such as short conduction intervals in the bypass tract (leading to a rapid ventricular rate, that is, a very fast heartbeat), metamorphosis of supraventricular tachycardia into atrial fibrillation, and the presence of multiple bypass tracts are risk factors for the occurrence of malignant arrhythmic events. The results of another study published in the same journal in 2014 found that the incidence of ventricular fibrillation during follow-up observations was much higher in asymptomatic preexcited patients than in those with symptomatic preexcitation, while the incidence of malignant arrhythmias was not significantly different. In other words, asymptomatic preexcited patients are more likely to develop ventricular fibrillation than symptomatic preexcited patients if no intervention is performed. The factors associated with the development of ventricular fibrillation are the short duration of the preexcited bypass (which predisposes to tachycardia and eventually ventricular fibrillation) and the metamorphosis of supraventricular tachycardia into atrial fibrillation. Thus, although the presence or absence of symptoms has a significant impact on the choice of treatment for preexcited patients, it is not the presence or absence of symptoms that affects the prognosis of patients, but rather the electrophysiological characteristics of the preexcited bypass itself. What does the clinical case tell us? We have encountered many patients in our clinical practice who, after effective resuscitation due to sudden malignant arrhythmic events, were confirmed to be previously asymptomatic preexcited patients. Some young patients come to the clinic because they have enlarged hearts, incomplete heart function, and can’t walk, but later they have a history of tachycardia. After years of follow-up, the “aging” heart was rejuvenated, the heart size was reduced, the heart function was improved, and the quality of life was improved, and the patient resumed a normal life. One of the most vivid cases I remember from my years of practice is: 8 years ago (end of 2007), 20-year-old Hu visited the clinic with an enlarged heart, when the left ventricle was already significantly enlarged to 80 mm (normally no more than 55 mm in a normal person of normal size), and was accompanied by a significant decrease in cardiac function. After the complete examination, he was found to have a preexcited bypass, which was then removed by radiofrequency ablation. After years of continuous medication adjustments, young Hu’s left ventricle has recovered to 56 mm this year and his heart function has improved significantly compared to before. This is because some preexcited bypasses grow in special locations (especially the right free wall bypass), which for some susceptible people can easily lead to the uncoordinated contraction activity of the left and right ventricles of the heart (the two ventricles do not work together, pulling each other’s strings and increasing the burden on the heart), which in the long run is like a rubber band being overstretched and finally losing its elasticity, eventually leading to heart enlargement, cardiac dysfunction, and even affecting life. How to prevent the problem before it happens and give reasonable treatment advice? It is recommended that patients with asymptomatic pre-excitation first need to improve their cardiac ultrasound to understand any structural abnormalities, and if not intervene, they need regular cardiac ultrasound follow-up afterwards to avoid severe heart enlargement without knowing it and delaying treatment. If the ECG is “intermittent preexcitation” (i.e., not all ECGs show preexcitation), most of them are “low-risk” and should be saved and followed by regular cardiology visits. If the preexcitation disappears during exercise (indicating that the preexcitation period is long, but the percentage is low), the patient may be “low-risk” and can be followed up regularly. If preexcitation persists during exercise, further consideration of transesophageal pacing electrophysiology or intracardiac electrophysiology is recommended. Intracardiac electrophysiology is the most accurate and minimally invasive test, which requires hospitalization, and provides a valid evaluation of the conduction function of the preexcited bypass, determination of relevant electrophysiological parameters, and determination of the presence of multiple bypasses. After electrophysiological examination, the electrophysiological characteristics of the preexcited bypass itself can be known. On this basis, the patient’s condition and other factors can be taken into account to determine whether to ablate and its advantages and disadvantages, and to decide the next treatment strategy. In general, if the electrophysiological examination has been performed, it is still recommended to directly perform radiofrequency ablation treatment to remove the excess preexcited bypass by radiofrequency ablation in order to avoid the occurrence of tachycardia in the future and to perform electrophysiological examination or radiofrequency ablation treatment again. In conclusion, for preexcitation, it is recommended to actively intervene to deal with it and unnecessarily leave so much risk to oneself.