Pre-excitation syndrome, in simple, layman’s terms, is an extra conductive circuit in the heart that tends to “short-circuit” (cause tachycardia) from time to time. The most common type of tachycardia it causes is “paroxysmal supraventricular tachycardia”. Pre-excitation syndrome is therefore an important cause of paroxysmal supraventricular tachycardia. In general, most of the episodes of paroxysmal supraventricular tachycardia in patients with preexcitation syndrome do not cause serious consequences. However, it would be an underestimation to assume that preexcitation syndrome does not lead to serious consequences. In some cases, it can cause sudden death. Why do you say this? That is because patients with pre-excitation syndrome can not only cause paroxysmal supraventricular tachycardia, but, more problematically, they are more likely to develop atrial fibrillation compared to the general population. As a rule, AF is not life-threatening in most cases (unless it causes, for example, a dislodged blood clot), and most AF is tolerable for the general population. However, in patients with pre-excitation syndrome, if AF occurs, i.e., when “pre-excitation” meets “atrial fibrillation,” they are like dry wood on fire, and a “cardiac short circuit” can occur that is much more serious than paroxysmal supraventricular tachycardia. This means that when “pre-excitation” meets “atrial fibrillation”, they are like a match made in fire, and a much more serious “short-circuit” event than paroxysmal supraventricular tachycardia can occur, with the possibility of sudden death due to ventricular fibrillation (the most malignant lethal arrhythmia). This can be seen in the attached ECG, which was recorded by Dr. Cheng during a pre-surgical episode and was alarming to the doctor. Therefore, radiofrequency ablation surgery is recommended for the radical treatment of patients with pre-excitation syndrome who have a history of tachycardia episodes, or suspicious palpitations, syncope, near syncope (brief blackness before the eyes), etc. With radiofrequency ablation, the success rate is high, and although there are surgical risks, they are usually minimal. In life, there are many patients who are reluctant to undergo radiofrequency ablation treatment because of concerns about the risks of the procedure. In fact, according to foreign studies, a patient with pre-excited syndrome who is reluctant to undergo radiofrequency ablation ablation surgery will be at risk for a number of cardiac events, and the cardiac risk he or she will assume by not undergoing the procedure will exceed the risk of surgical complications if he or she undergoes radiofrequency ablation, if delayed for several years. Therefore, it is advisable for patients with pre-excited syndrome to seek an evaluation of their condition by an experienced physician and choose the appropriate treatment.