A 28-year-old female presents to her general practitioner's office complaining of recurrent, sudden-onset palpitations and lightheadedness over the past six months. She describes these episodes as rapid and pounding, lasting from a few minutes to an hour, often subsiding with deep breathing exercises or splashing cold water on her face. However, the last episode, which occurred yesterday, was more severe and did not resolve with her usual maneuvers, prompting a visit to the emergency department. During that visit, an electrocardiogram revealed a rapid narrow-complex tachycardia at a rate of 195 beats per minute. A bolus of intravenous adenosine was administered, which successfully terminated the tachycardia but transiently unmasked a new ECG finding characterized by a shortened PR interval and a prominent delta wave, subsequently confirming a diagnosis of Wolff-Parkinson-White (WPW) syndrome. She denies any chest pain, shortness of breath, or syncope. Her past medical history is otherwise unremarkable, and she takes no regular medications. On examination today, her temperature is 36.9°C, blood pressure is 125/80 mmHg, pulse is 72 beats per minute and regular, respirations are 16 per minute, and oxygen saturation is 98% on room air. Cardiac auscultation reveals regular S1 and S2 with no murmurs, gallops, or rubs. Pulmonary and abdominal exams are unremarkable. Given her symptomatic presentation and confirmed diagnosis, what is the most appropriate acute therapeutic intervention for a similar future symptomatic episode and the subsequent long-term strategy to prevent recurrence?

A 32-year-old male presents to the Emergency Department complaining of sudden-onset, severe palpitations, lightheadedness, and a sensation of near-fainting that began approximately 30 minutes prior. He reports a history of intermittent "racing heart" episodes since his late teens, often self-resolving, which he previously attributed to anxiety. These episodes have become more frequent and prolonged in recent months. He denies chest pain, shortness of breath, or focal neurological deficits. On examination, he appears anxious but is alert and oriented. His temperature is 36.8°C, blood pressure is 105/65 mmHg, heart rate is 220 beats/min, and respiratory rate is 16 breaths/min. Cardiac auscultation reveals a rapid, regular rhythm with no murmurs. Lung sounds are clear bilaterally. Peripheral pulses are palpable and symmetrical. A 12-lead electrocardiogram is immediately obtained, revealing a wide QRS complex tachycardia with a QRS duration of 0.16 seconds, a superior axis, and subtle evidence of retrograde P waves. Prior EKG from a routine physical examination 6 months ago showed a short PR interval and a delta wave. Based on this presentation, what is the most probable underlying diagnosis and the most appropriate initial pharmacological management strategy for this patient?

A 45-year-old woman presents to an urgent care center complaining of sudden onset palpitations, lightheadedness, and shortness of breath that began an hour ago. She reports a history of occasional "fast heartbeats" but denies prior syncopal episodes. On examination, she appears pale and anxious, with a rapid, irregular pulse. Her vital signs are: heart rate 180 beats/min, blood pressure 85/50 mmHg, respiratory rate 24 breaths/min, and oxygen saturation 92% on room air. Cardiac auscultation reveals a rapid, irregularly irregular rhythm. An EKG shows a wide complex tachycardia with an irregularly irregular rhythm. Given this presentation, what is the most likely diagnosis and the immediate management strategy?

A 52-year-old woman presents to a general hospital setting with an abrupt onset of severe palpitations, profound dizziness, and near-syncope that started approximately 30 minutes ago. She describes the sensation as her 'heart racing out of control.' She has a medical history notable for well-controlled essential hypertension, for which she takes lisinopril, and occasional panic attacks. She denies any chest pain, shortness of breath, or focal neurological deficits. On examination, her temperature is 37.0°C, blood pressure is 95/60 mmHg, pulse is 195 beats/min and regular, respiratory rate is 28 breaths/min, and oxygen saturation is 98% on room air. She appears acutely distressed, pale, and is disoriented to time and place, responding slowly to verbal commands. Auscultation reveals clear lung sounds bilaterally and a rapid, regular rhythm with no murmurs, rubs, or gallops. Peripheral pulses are weak but palpable. Capillary refill is delayed at 4 seconds. An electrocardiogram is immediately obtained, revealing a wide complex tachycardia with a rate of 195 bpm, a QRS duration of 0.16 seconds, and a prominent delta wave in leads V1-V3. What is the most likely diagnosis and the immediate definitive management for this patient?