We often encounter some patients in the clinic who usually have no symptoms such as palpitations, chest tightness, or black clouding, and are found to have ECG manifestations of pre-excitation syndrome during routine physical examination. Some patients are very nervous, fearing that they may have a malignant arrhythmia event that may lead to sudden death; while others do not take it seriously, thinking that there is no tachycardia attack anyway and there are no discomfort symptoms in general, so they do not do further examination. So what exactly is the pre-excitation syndrome? Xu Jin, Department of Cardiology, Shanghai Renji Hospital Pre-excitation syndrome (WPW) is the presence of one or more atrioventricular bypasses (APs) between the patient’s atria and ventricles, which has characteristic manifestations of ventricular pre-excitation on the electrocardiogram, and in some patients can have episodes of atrial fold tachycardia (a kind of supraventricular tachycardia, sudden onset and stop, with an absolutely uniform ventricular rate of 150-220 beats/min) or atrial fibrillation (an attack with an absolutely irregular ventricular The ventricular rate can be very fast when combined with bypass preexcitation, resulting in ventricular tachycardia, ventricular fibrillation, and other malignant arrhythmic events, and patients can experience blackouts, syncope, and even sudden death). Since the current cardiac radiofrequency ablation technique to block the atrioventricular bypass for the radical treatment of preexcitation syndrome is well established, with a success rate of more than 95%, radiofrequency ablation is recommended for patients with symptoms. So is radiofrequency ablation needed for asymptomatic patients with preexcitation syndrome? A prospective follow-up study published in 2012 in Circulation, a leading international cardiovascular journal, found that in patients with preexcitation syndrome with one episode of supraventricular tachycardia, without catheter ablation, a malignant arrhythmic event (defined as a potentially life-threatening arrhythmogenic episode with one episode of persistent atrial fibrillation combined with a minimum preexcitation RR interval of 250 ms recorded over a 5-year follow-up interval of 250 ms; or a very rapid episode of atrial fibrillation or ventricular fibrillation resulting in sudden loss of effective blood flow, hemodynamic disturbance, and cardiac arrest requiring cardiopulmonary resuscitation and/or electric defibrillation) was 7% and the incidence of hemodynamic disturbance and cardiac arrest was 1.4%. The presence of short AP-AERP (short parasternal tachycardia that can cause very fast ventricular rates) and multiple parasternals can convert supraventricular tachycardia (ARVT) to atrial fibrillation (AF), leading to malignant arrhythmic events and sudden death. In patients with asymptomatic pre-excitation syndrome, as in symptomatic patients, the presence of short AP-AERP, conversion of AVRT to AF, and multiple bypasses are also risk factors for malignant arrhythmic events. The prognostic factors for poor outcome in asymptomatic and symptomatic preexcited patients are the same, and the prognosis is related to the intrinsic electrophysiological properties of the bypass, not to the symptoms. We have encountered several patients in our clinic who had only the ECG manifestation of preexcitation in the past, and no further examination was performed because of the absence of symptoms, but in a certain stressful situation (some patients after drinking alcohol or during exercise or emotional excitement), sudden onset of atrial fibrillation with preexcitation precession occurred, hypotensive shock, blackout, and syncope, etc. Finally, fortunately, they were rescued in time and out of danger by emergency electrical cardioversion; after that we gave Afterwards, we performed radiofrequency ablation to cure the preexcited collateral tract, and the patients recovered. These patients were very dangerous at the onset, and if they were not rescued in time, they would have died suddenly. So how can we prevent the problem before it happens and identify patients with potential risk of sudden death from the many patients with preexcitation syndrome? According to our experience, combined with the 2012 International PACES/HRS Expert Consensus: two major categories of tests, invasive and non-invasive, need to be applied to patients with pre-excitation syndrome for risk stratification. Non-invasive tests such as electrocardiogram: in patients with preexcitation combined with atrial fibrillation, measurement of the shortest preexcitation RR interval (SPERRI) allows a more realistic evaluation of the antegrade function of the bypass; if the SPERRI is between 220 ms and 250 ms, especially shorter than 220 ms, it is considered a risk factor for the development of sudden cardiac death; if it shows intermittent ventricular preexcitation, it is relatively low risk . However, most patients only have ECG manifestations of sinus rhythm combined with pre-excitation and have not had atrial fibrillation, so it is impossible to evaluate, and when they have atrial fibrillation, they are at risk in some patients. How to detect high-risk patients among asymptomatic patients with preexcitation? Invasive electrophysiological examination becomes necessary. Although the mention of invasive here may scare some patients, it is actually a minimally invasive test with minimal risk that allows a valid evaluation of bypass antegrade function, determination of AP-AERP, and determination of the presence of multiple bypasses; if the AP-AERP is found to be short on electrophysiological examination or if multiple bypasses are present, then the probability of a malignant arrhythmic event is high and we can perform radiofrequency ablation at the same time to eradicate the bypasses. Shanghai Renji Hospital is the first hospital in China to perform electrophysiological examination and radiofrequency ablation for the treatment of pre-excitation syndrome, supraventricular tachycardia and various arrhythmias. If you have preexcitation syndrome, whether you have symptoms or not, you can go to our hospital for further examination and treatment.