Abstract
The Wolff Parkinson White (WPW) pattern is the most common form of ventricular preexcitation. It may present as an incidental finding on a routine electrocardiogram in completely asymptomatic patients, in which case it is called WPW pattern; or it may be accompanied by episodes of paroxysmal tachyarrhythmias, known as WPW syndrome. Because patients with this syndrome have a higher risk of sudden death than general population, it is important to know the electrocardiographic manifestations of this syndrome in order to make an accurate diagnosis. We present an electrocardiographic case of WPW in sinus rhythm, its physiological bases and most common findings will be discussed.