Racing Heart, Chest Pain in a 65-year-old Man

VIDEO: Palpitations persist in ED; no history of cardiac issues. Incident is first of its kind for this patient. Watch the interview.

Patient presents with "racing heart," weakness, mild chest pain. No history of similiar symptoms or of stroke, other cardiac issues. Denies ETOH, tobacco use. PMH: HTN; hyperlipidemia; chronic back pain. Current meds: lisinopril; hydrocodone/acetaminophen; simvastatin. Vitals: HR: 98 bpm, RR: 20, BP: 175/86; SpO₂: 98%.

Which of the following is the most likely diagnosis?