※ 引述《ejackylate (小飞机)》之铭言： : 10.下列何者与心室颤动(ventricular fibrillation)的成因较无关? : (A)心脏肥厚(hypertrophy) (B)心肌缺血(ischemia) : (C)血钾过高(hyperkalemia) (D)Purkinje system传导阻滞 : 答案：A : 但查了E-medicine: http://emedicine.medscape.com/article/158712-overview : 在下面的Causes中有 Hypertrophic cardiomyopathy : 故本题无答案 建议送分 这则paper开头就有说 http://findarticles.com/p/articles/mi_6875/is_4_6/ai_n28400194/ Hypertrophic cardiomyopathy (HCM) is associated with an increased incidence of supraventricular and ventricular arrhythmias. Atrial fibrillation (AF) is the most common arrhythmia in HCM with a prevalence of 20% and an annual incidence of two percent per year. 再来看这是Hypertrophic cardiomyopathy with atrial fibrillation的心电图 以及相关解释的内文我觉得蛮有力的 http://cardiophile.org/2009/01/hypertrophic-cardiomyopathy-with-atrial-fibrillation.html Atrial activity is seen as irregular fibrillary waves suggesting atrial fibrillation. The QRS complexes have a large amplitude in chest leads overlapping between the leads. Tall R waves in lateral leads and deep S waves in anterior leads along with gross ST segment depression with T wave inversion in lateral leads are suggestive of severe left ventricular hypertrophy. The QRS width is also increased to about 120 msec mimicking left bundle branch block. The ECG is from a case of advanced hypertrophic cardiomyopathy with atrial fibrillation. Development of atrial fibrillation leads to cardiac decompensation in hypertrophic cardiomyopathy due to loss of atrial kick. In a hypertrophied ventricle the booster effect of atrial contraction is very important for diastolic filling. Even though the contribution of atrial contraction to ventricular filling in a normal person is about 15 – 20 %, it may be over 30% in an individual with diastolic dysfunction as in hypertrophic cardiomyopathy. When the ventricular filling decreases, it reduces the cardiac output as well as an increase in the left ventricular outflow obstruction. This is because the severity of left ventricular outflow tract obstruction increases when the ventricular cavity size decreases. 再来就是美国心脏协会的journal(被引用次数是181次) http://content.onlinejacc.org/cgi/content/abstract/15/6/1279 内容是有关Atrial fibrillation in hypertrophic cardiomyopathy的长期研究 最後 重点是要试着从教科书上的叙述来跟申覆委员讲了 guyton中文版第十一版第152页的解释中 首先ventricular fibrillation是心脏冲动在心室肌肉间爆冲所引发 冲动先刺激一部份心室肌肉，再换其他部分 导致心肌永远无法一起做协调性的收缩 然而心肌协调性的收缩却是心脏做帮浦循环所必须的 ventrcular fibrillation下尽管有大量刺激讯息流过心室，心室却不扩张也不收缩 只维持部分收缩的不稳定状态，几乎无法抽送出血液 另一方面guyton说特别会引起fibrillation的原因有二 1. 心脏受到突然的电流刺激 2.心肌或特化的传递系统局部缺血 以上是GUYTON对ventricular fibrillation的叙述 让我们看上面fibrillation的原因的第二点 接下来要证明的 就是hypertrophy会造成所谓传导系统的局部缺血 使得传导路径出问题 hypertrophic cardiomyopathy的feature中 Myocardial hypertrophy impinging on the left ventricular (LV) cavity, narrowing the LV outflow tract during systole, can cause dynamic obstruction 也就是心脏肥大会侵犯到左心室的腔室容量 使心收缩期的左心室outflow受阻 也就是体循环的动脉血出不去 ok,guyton中文版第十一版第153页有说 ventricular fibrillation的传导路径出问题分为两种 一种是传导路径的延长：其发生在心脏扩张时 一种是传导速率减慢：可能是因为purkinje fiber传导受阻 肌肉局部缺血 血钾过高 以及许多其他原因 一种是心室不反应期的缩短：比较常出现在对药物的反应 注意关键字："许多其他原因" ventricular fibrillation目前的理论依据 是所谓的"circus movement" 也就是说当心脏冲动传遍整个心脏到达心房时 整个心室肌肉还是处於不反应期 冲动无法继续传递 因而中止 直到SA node产生下一个动作电位时，心脏才有所反应 今天hypertrophy造成左心室outflow受阻 产生局部缺血 进而影响到ventricular fibrilation http://content.onlinejacc.org/cgi/content/abstract/15/6/1279 这也是以上美国心脏协会这篇journal说明hypertrophy会造成 ventricular fibrillation 的原因 --

※ 发信站: 批踢踢实业坊(ptt.cc) ◆ From: 192.192.93.82 ※ 编辑: jfc7788 来自: 192.192.93.82 (08/04 10:45)