WPW is an ECG pattern characterized by a short PR interval followed by a delta-wave and a prolonged QRS duration. The duration may be >120 millisec but it can be shorter depending upon the degree of fusion. These characteristics are due to aberrant conduction of ventricular activation through an accessory pathway. It occurs in 1 out of 10,000 individuals and can be entirely asymptomatic or associated with tachycardia and palpitations. There is concern that individuals with WPW are at risk of ventricular fibrillation if they were to go into atrial fibrillation. When WPW is present the ST segments cannot be used to identify ischemia and Q waves are actually negative delta-waves and not due to infarction. It is one of the ECG patterns where the R wave can be greater than S wave in V1 and V2.

The individual who is incidentally found to have this ECG finding will usually be otherwise normal. The individual should be questioned as to symptoms of palpitations or syncope. Also, a family history of syncope or sudden death could have significance. If any of these issues are positive, referral to an electrophysiologist is appropriate. SVT's associated with WPW usually can be suppressed with procainamide. Other drugs including beta-blockers can impede conduction through the normal pathways exacerbating the re-entry arrhythmia. If a patient presents with chest pain, the ECG is eliminated as a diagnostic tool and enzymes or nuclear perfusion testing is required.