左心衰竭的早期症状是（）。
A．心界扩大
B．室性奔马律
C．浮肿
D．劳力性呼吸困难
参考答案：D
解析：
[考点] 左心衰竭的早期症状与体征
[分析]： 室性奔马律是舒张期的一种额外心音，它的产生机制一般认为是在心肌收缩力减退、心室壁顺应性减退情况下，在舒张早期心房血液快速注入左心室时引起已过度充盈的心室壁产生振动所致，从血流动力学角度看，它反映左室允盈压、左房压、肺毛细血管楔嵌压明显升高，是反映左室功能不全的一个体征。 左心衰竭最早出现的临床症状是劳力性呼吸困难，因进行体力活动时，回心血量增加，左心房压上升，肺淤血加重，所以山现呼吸困难。随着心功能不伞的加重，患者可出现夜间阵发性呼吸困难、端坐呼吸以及心源性哮喘。
The bell for class rang. All the students took out their 46 , waiting for the teacher. Our Chinese teacher, Miss Liu, had told us before that we were going to write a composition 47 class. A minute passed, and another, 48 the teacher didn't appear. We began to wonder what was the matter with her. Was she ill? Or had she forgotten about the class? 49 could tell. Soon some students began to study other subjects, some students began to talk and even made 50 . About ten minutes later, the door opened and Miss Liu 51 came in, smiling. She didn't say sorry to the class. We felt 52 angry. The teacher often told us never to be late for class and said it was 53 manners to be late. She also said that if we were late, we should make an apology (道歉) 54 at once or after class. But now she was late and had kept the whole class waiting for such a long time and didn't even tell us the reason. It was unfair. At this moment, Miss Liu picked up a piece of chalk(粉笔) and 55 "T  eacher IsLate" on the blackboard and said that was the topic of our composition today. All of us smiled and understood what the teacher meant.
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