How is the PR interval affected in Wolf Parkinson White syndrome?

In Wolf-Parkinson-White (WPW) syndrome, the PR interval is characteristically shortened due to the presence of an accessory pathway, which allows electrical impulses to bypass the normal conduction route of the heart. This accessory pathway connects the atria and ventricles directly, leading to earlier depolarization of the ventricles. As a result, the electrical impulses reach the ventricles more quickly than they would if they were solely traveling through the standard conduction system, which includes the atrioventricular (AV) node.

The typical PR interval duration is around 120 to 200 milliseconds, and in the case of WPW, it is often less than 120 milliseconds, indicating that the electrical impulses are conducted more rapidly than usual. This shortened interval can sometimes be observed on an electrocardiogram (ECG) as one of the defining characteristics of WPW syndrome, along with a delta wave.

Understanding how WPW affects the PR interval is important for recognizing the condition and considering the implications it has for arrhythmias that can occur, such as paroxysmal supraventricular tachycardia.