Fesmire F M
Department of Emergency Medicine, Erlanger Medical Center, University of Tennessee College of Medicine, Chattanooga Unit, USA.
Ann Emerg Med. 1995 Jul;26(1):69-82. doi: 10.1016/s0196-0644(95)70241-5.
It is common knowledge that the ECG diagnosis of completed myocardial infarction in the presence of left bundle-branch block (LBBB) is extremely difficult and often impossible. More than 50 rules have been proposed as criteria for interpreting Q-wave equivalents superimposed on the QRS complex in the presence of LBBB. However, because of misinterpretation of the available literature, physicians frequently recommend that patients with chest pain in the presence of LBBB receive thrombolytic therapy or urgent coronary arteriography on the basis of the assumption that acute injury and ischemia cannot be interpreted in the presence of LBBB. Unfortunately, many physicians fail to realize that although completed infarction is difficult to confirm in the presence of LBBB, ongoing ischemia and injury can be detected in the presence of LBBB and may be seen as often as they are in the presence of normal cardiac conduction. A deflection of the J point (and ST segment) in the direction of the major QRS complex or an elevation of the ST segment of more than 7 to 8 mm opposite the direction of the major QRS complex has been demonstrated to have a sensitivity of more than 50% in detecting acute injury, with a specificity of more than 90%. During the first half of an ongoing prospective study of the use of continuous 12-lead ECG monitoring in the emergency department, we encountered five patients with final diagnoses of acute myocardial infarction in the presence of LBBB who demonstrated significant ECG changes while undergoing continuous ST-segment monitoring with frequent serial ECGs. The five different locations of the infarcts in these five patients were posterior, posterolateral, inferior, anterior, and anterolateral. We present these patients' cases to demonstrate the ECG characteristics of acute injury in the presence of LBBB.
众所周知，在存在左束支传导阻滞（LBBB）的情况下，心电图诊断完全性心肌梗死极其困难，甚至常常无法诊断。已经提出了50多条规则作为解释LBBB存在时叠加在QRS波群上的Q波等效物的标准。然而，由于对现有文献的误解，医生经常建议LBBB伴有胸痛的患者接受溶栓治疗或紧急冠状动脉造影，其依据是认为在LBBB存在的情况下无法解释急性损伤和缺血。不幸的是，许多医生没有意识到，虽然在LBBB存在时难以确诊完全性梗死，但在LBBB存在时可以检测到正在发生的缺血和损伤，而且其出现频率与正常心脏传导时一样。已证实，J点（和ST段）在主要QRS波群方向的偏移或与主要QRS波群方向相反的ST段抬高超过7至8mm，在检测急性损伤时灵敏度超过50%，特异性超过90%。在急诊科进行的一项关于连续12导联心电图监测应用的前瞻性研究的前半段期间，我们遇到了5例最终诊断为LBBB合并急性心肌梗死的患者，他们在接受连续ST段监测及频繁系列心电图检查时表现出明显的心电图变化。这5例患者梗死的5个不同部位分别是后壁、后侧壁、下壁、前壁和前侧壁。我们展示这些患者的病例以说明LBBB存在时急性损伤的心电图特征。
