Arthur N., a 64-year-old gentleman, presents to his family physician because he is noticing increasing difficulty walking because of breathlessness. He states that he cannot put a finger on when it first began "except that he is aware that he was not as fit" as he should be. Arthur has always enjoyed his walking. However, over the last six months, he has noticed that any incline will make him breathless to the point that friends will remark on it, and he simply has to stop walking. In addition, climbing stairs has become quite difficult. He remarks that he has not been breathless at rest, nor at night-time. He has not noticed any swelling of his ankles. Arthur states that he smoked lightly about twenty years ago. His occupational history is unremarkable and there is no history of heart disease.