While the overall risk is approximately 2.4 per 1000 person years, the risk in an individual is dependent on the properties of the accessory pathway causing pre-excitation.A higher risk accessory pathway may be suggested by a history of syncope, but risk stratification is best performed by assessing how frequently a pathway can conduct impulse to the ventricles, usually via programmed electrical stimulation (PES) in the cardiac electrophysiology laboratory. This is an invasive but generally low-risk procedure during which the atria are stimulated to try to induce tachycardia. If a tachycardia involving the accessory pathway can be triggered, the cardiologist can then assess how rapidly the accessory pathway is able to conduct. The faster it can conduct, the higher the likelihood the accessory pathway can conduct fast enough to trigger a lethal tachycardia.High-risk features that may be present during PES include an effective refractory period of the accessory pathway less than 250 ms, multiple pathways, septal location of pathway, and inducibility of supraventricular tachycardia (AVRT, atrial fibrillation). Individuals with any of these high-risk features are generally considered at increased risk for SCD or symptomatic tachycardia, and should be treated accordingly (i.e. : catheter ablation).It is unclear whether invasive risk stratification (with PES) is necessary in the asymptomatic individual.
This combination of atrial fibrillation and WPW is considered dangerous, and most antiarrhythmic drugs are contraindicated.When an individual is in normal sinus rhythm, the ECG characteristics of WPW are a short PR interval (less than 120 milliseconds in duration), widened QRS complex (greater than 120 milliseconds in duration) with slurred upstroke of the QRS complex, and secondary repolarization changes (reflected in ST segment-T wave changes).In individuals with WPW, electrical activity that is initiated in the SA node travels through the accessory pathway, as well as through the AV node to activate the ventricles via both pathways. Since the accessory pathway does not have the impulse slowing properties of the AV node, the electrical impulse first activates the ventricles via the accessory pathway, and immediately afterwards via the AV node. This gives the short PR interval and slurred upstroke of the QRS complex known as the delta wave.In case of type A pre-excitation (left atrioventricular connections), a positive R wave is seen in V1 ("positive delta") on the precordial leads of the electrocardiogram, while in type B pre-excitation (right atrioventricular connections), a predominantly negative delta wave is seen in lead V1 ("negative delta").People with WPW may have more than one accessory pathway – in some cases, as many as eight abnormal pathways have been found. This has been seen in individuals with Ebsteins anomaly.Wolff–Parkinson–White syndrome is sometimes associated with Lebers hereditary optic neuropathy, a form of mitochondrial disease. Risk stratification
WPW carries a small risk of sudden death, presumably due to rapidly conducted atrial fibrillation causing ventricular fibrillation.