What typically characterizes the ECG of a patient with Wolff-Parkinson-White syndrome?

The presence of delta waves is a hallmark characteristic of the ECG in patients with Wolff-Parkinson-White (WPW) syndrome. Delta waves are seen as a slurring or a slow upstroke in the QRS complex and result from the pre-excitation of the ventricles due to the existence of an accessory pathway (the Bundle of Kent) that bypasses the normal conduction system. This early activation leads to a QRS complex that is wider and can be confused with a bundle branch block.

In contrast, the other choices do not typically characterize WPW syndrome. The prolonged QT interval is associated with different conditions, such as congenital long QT syndrome or drug-induced QT prolongation. Inverted T waves may indicate myocardial ischemia or other conditions but are not a characteristic finding in WPW syndrome. Lastly, a normal sinus rhythm can occur in many situations but does not reflect the unique pre-excitation findings that define WPW syndrome. Therefore, the presence of delta waves is the defining feature in the ECG of this condition.