mrcem2-0201

mrcem2-0201

A 42-year-old Caucasian man presents with gradually worsening shortness of breath on exertion that has been ongoing for the past four weeks. The breathlessness is worse when lying flat, and he has noticed his ankles have become swollen. This morning he had a small amount of blood in his sputum. He is currently 32 weeks pregnant, and his pregnancy is progressing normally. On examination, you note that he has a tapping apex beat and a low-volume pulse. On auscultation, you note a loud first heart sound and a mid-diastolic murmur at the apex.
What is the SINGLE most likely diagnosis?