[名词解释] 蹲踞现象

心内膜弹力纤维增生症(endocardialfibroelastosis) 阵发性缺氧发作 肺动静脉瘘特征性临床表现为() ["A．呼吸困难","B．红细胞增多症","C．颜面血管扩张","D．心外性杂音","E．咯血"] atrialseptaldefect 诊断纵隔恶性畸胎瘤的指征是() ["A．位于前纵隔","B．肿瘤直径超过5cm","C．含脂肪信号","D．局部受侵，肿瘤边缘不规则","E．以上均是"] 蹲踞现象