A 68-year-old man presents to the emergency department with increasing shortness of breath, fatigue, and swelling in his legs for the past 3 weeks. He reports difficulty breathing while lying flat and has been using three pillows to sleep at night. Over the last few days, he has noticed that his shoes and socks feel tight, and he has gained approximately 4 kg in weight in the past two weeks. He also complains of a persistent dry cough, particularly at night, and mentions a feeling of heaviness in his chest but denies chest pain, palpitations, or recent infections. A diagnosis of heart failure is suspected in this patient.