A 30-year-old female presents with panic attacks that began 2 months ago. She reports episodes of sudden-onset chest tightness, heart racing, shortness of breath, dizziness, and a feeling she is "going to die." Episodes last 10-15 minutes and occur 2-3 times per week. She has been to the emergency department twice; both times cardiac workup was negative. What should the PMHNP assess to confirm the diagnosis?