A 45-year-old male presents to a psychiatric clinic after referral from his primary care provider. He reports persistent worry over the past 14 months that he has an undiagnosed cardiac condition despite three normal cardiac evaluations, including echocardiogram, stress test, and Holter monitoring. He checks his pulse approximately 20 times daily, frequently searches medical websites for cardiac symptoms, and has visited the emergency department 8 times in the past year for perceived palpitations. Physical examination and all diagnostic workups have been unremarkable. He reports minimal somatic symptoms but remains convinced that something has been missed. What is the most appropriate diagnostic consideration?