Review Question - QID 214399

A 37-year-old man presents to the emergency department with shortness of breath and chest pain. The patient states that his symptoms started a few days ago and have been gradually worsening. He recently had a cold from which he recovered but is otherwise healthy. His temperature is 98.3°F (36.8°C), blood pressure is 107/65 mmHg, pulse is 128/min, respirations are 18/min, and oxygen saturation is 99% on room air. Physical exam is notable for clear breath sounds, jugular venous distension, bilateral lower extremity edema, and obesity. Cardiac auscultation demonstrates an early diastolic sound. An ultrasound demonstrates a normal ejection fraction with restricted ventricular filling. Which of the following is the most likely diagnosis?