Q. A 38-year-old man with a history of poor nutrition and alcoholism presents to the emergency department complaining of shortness of breath, particularly when lying flat at night. He also mentions he has been feeling very tired lately and has noticed swelling in his legs. On examination, his heart rate is 115 beats per minute, blood pressure is 130/85 mmHg, and jugular venous pressure is elevated. His lower extremities are noticeably edematous, and auscultation of the heart reveals a gallop rhythm. Chest X-ray shows evidence of cardiomegaly. Based on the patient's history and clinical presentation, what is the most likely diagnosis?