Mr. Zhang is an 83-year-old retired carpenter who ...

Mr. Zhang is an 83-year-old retired carpenter who still does “odd jobs” for friends and neighbors. His wife has pleaded with him to relax, but he ignores her. Despite having chest pains (angina) and periods of confusion, Mr. Zhang doesn’t trust doctors and has stubbornly refused to have a check-up. Recently, though, after several episodes of syncope (fainting) while he was hauling lumber, he grudging agreed to see a physician. On physical examination, the physician noted a murmur during systole (described as systolic ejection murmur), a palpable S4, and a significantly diminished aortic component of S2. His carotid artery pulse was weak, and had a delayed upstroke. The physician ordered a cardiac catheterization, which showed a pressure gradient of 100 mm Hg between the left ventricle and the aortic during systole, consistent with aortic stenosis. Question: 1.In aortic stenosis, there is significant narrowing of the aortic valve opening. Why does this narrowing cause a murmur？ Why does this murmur occur during systole？ What is the timing of the murmur with respect to S1 and S2？ 2. What are the component of a normal S2, and why did Mr. Zhang have a diminished aortic (component) of S2？