Snapshot A 17-year-old girl presents to the emergency room with lightheadedness and palpitation. Her pulse is 250/min and she is hemodynamically stable. An electrocardiogram shows an antidromic atrioventricular reentrant tachycardia. She is given procainamide with a resolution of the arrhythmia. Now in sinus rhythm, she is found to have a widened QRS, delta wave, and shortened PR interval on the electrocardiogram. Introduction Clinical definition a ventricular pre-excitation syndrome resulting in an aberrant conduction tract that bypasses the atrioventricular (AV) node Associated conditions Ebstein anomaly hypertrophic cardiomyopathy Epidemiology Risk factors family history Etiology Can be familial Pathogenesis ventricular pre-excitation results from an aberrant conduction tract from the atria to the ventricle, known as the bundle of Kent this fast accessory tract bypasses the slowest-conducting AV node ventricles then depolarize earlier than normal this causes the classic delta wave and widened QRS administration of calcium channel blockers or digoxin will worsen a supraventricular tachycardia (SVT) caused by WPW syndrome calcium channel blockers and digoxin block conduction in the AV node and will force more conduction down the aberrant tract, worsening WPW syndrome Presentation Symptoms can be asymptomatic if symptomatic, patients will present with an arrhythmia palpitations lightheadedness syncope dizziness chest pain Physical exam tachycardia Studies Electrocardiogram (ECG) delta wave short PR interval widened QRS complex may have supraventricular tachycardia if symptomatic Making the diagnosis based on clinical presentation and ECG Differential Myocardial infarction distinguishing factor ST elevation on ECG Bundle branch block distinguishing factor widened and abnormal terminal portion of QRS portion on ECG Treatment Management approach drugs that delay AV node conduction is typically contraindicated in these patients, unless patients have confirmed orthodromic AVRT Medical procainamide indications for patients who are hemodynamically stable for patients with antidromic AVRT (wide QRS complexes) or atrial fibrillation due to WPW syndrome adenosine or calcium channel blocker indication for patients with orthodromic AVRT (narrow QRS complexes) Non-operative electrical cardioversion indication for all patients who are hemodynamically unstable due to arrhythmia radiofrequency catheter ablation indication long-term definitive therapy for patients with WPW syndrome Complications Sudden cardiac death Prognosis Can present with the following arrhythmias atrioventricular reentrant tachycardia (AVRT) most commonly as orthodromic AVRT narrow QRS complexes (< 120 ms) less commonly as (5%) antidromic AVRT wide QRS complexes atrial fibrillation atrial flutter ventricular tachycardia ventricular fibrillation and sudden death