Wolff-Parkinson-White (WPW) Syndrome: This condition is characterized by an accessory electrical pathway in the heart, leading to pre-excitation of the ventricles. The widened QRS complex (134 ms) and symptoms of pre-syncope and palpitations are consistent with WPW syndrome, especially in a young individual.

Bundle Branch Block: Given the widened QRS complex, a bundle branch block (either left or right) could be a possible diagnosis. However, the presence of palpitations and pre-syncope might suggest a more dynamic or unstable condition.
Ventricular Tachycardia: Although less common in a young individual without underlying heart disease, ventricular tachycardia could present with a wide QRS complex and symptoms of palpitations and pre-syncope.

Hypertrophic Cardiomyopathy (HCM): This condition can lead to sudden cardiac death, especially in young athletes. While the widened QRS might not be directly indicative of HCM, the symptoms of pre-syncope and palpitations warrant consideration of this potentially lethal condition.
Long QT Syndrome: This condition can cause life-threatening arrhythmias. Although the QRS duration is provided, the QT interval is not mentioned, making it crucial to assess for long QT syndrome, especially given the symptoms.
Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC): Another condition that can lead to sudden cardiac death, ARVC might present with ventricular arrhythmias and could be considered in the differential, especially if there's a family history or other suggestive findings.

Lyme Carditis: Caused by Lyme disease, this condition can lead to various cardiac manifestations, including conduction abnormalities and arrhythmias. While rare, it's an important consideration in endemic areas or with suggestive exposure history.
Cardiac Sarcoidosis: This condition can cause a wide range of cardiac symptoms, including arrhythmias and conduction abnormalities. It's less common but should be considered, especially if other systemic symptoms are present.