Sgarbossa E B
Department of Cardiology, Rush-Presbyterian Medical Center, Chicago, IL 60612, USA.
J Electrocardiol. 2000;33 Suppl:87-92. doi: 10.1054/jelc.2000.20324.
Uncomplicated left bundle branch block (LBBB) is characterized by true ST-segment shifts resulting from delayed repolarization in the left ventricle with respect to the right ventricle. When acute coronary occlusions develop in the setting of previous or new LBBB, 12-lead eCG manifestations of injury may also appear. They consist of a more pronounced ST-segment elevation, of ST-segment deviations opposite to those of uncomplicated LBBB, or both. We have reported that the only 3 independent ECG signs of acute MI during LBBB among patients with chest pain or history of coronary disease are: ST elevation > or = 1 mm in leads with a positive QRS, ST-depression > or = 1 mm in V1 to V3, and ST elevation > or = 5 mm in leads with a negative QRS. In our study, the clinical prediction rule score values of these signs were 5; 3; and 2, respectively. A score > or = 3 made a diagnosis of MI with a 90% specificity and a score of 2 with > 80%, specificity. Recent validation studies have confirmed that the presence of any of these ECG signs is associated with a sensitivity of 44 to 79% and a specificity of 93 to 100%. Sensitivity increases if serial or previous ECGs are available for comparison. Interobserver agreement is very high. While current practice guidelines recommend thrombolysis for all patients with chest pain and LBBB, concern among physicians about hemorrhagic stroke prevents many of these patients from receiving timely treatment. In a population with LBBB and chest pain where our proposed ECG criteria were not ascertained, only 73% of eligible patients received thrombolysis; on the other hand, 48% of patients with no biochemical evidence of MI were thrombolyzed. For the latter group, the clinical prediction rule had a score of 0. Instead, 79% of patients with confirmed acute MI had a prediction rule score > or =2. Similar values applied to a subgroup of patients with serial ECGs. We propose that thrombolysis among patients with chest pain and LBBB be decided on the basis of a systematic ECG review to "rule patients in". This provision may result in both a significant reduction in the number of patients without infarction who receive thrombolysis and in timely treatment of those who do have MI.
单纯性左束支传导阻滞（LBBB）的特征是，相对于右心室，左心室复极延迟导致真正的ST段移位。当在既往或新发LBBB的情况下发生急性冠状动脉闭塞时，12导联心电图（ECG）也可能出现损伤表现。这些表现包括更明显的ST段抬高、与单纯性LBBB相反的ST段偏移，或两者皆有。我们曾报道，在胸痛或有冠心病病史的患者中，LBBB期间急性心肌梗死（MI）仅有的3个独立心电图征象为：QRS波正向的导联中ST段抬高≥1mm、V1至V3导联中ST段压低≥1mm以及QRS波负向的导联中ST段抬高≥5mm。在我们的研究中，这些征象的临床预测规则评分值分别为5、3和2。评分≥3对MI的诊断特异性为90%，评分为2时特异性>80%。近期的验证研究证实，这些心电图征象中的任何一项出现时，敏感性为44%至79%，特异性为93%至100%。如果有系列或既往心电图可供比较，敏感性会增加。观察者间的一致性非常高。虽然目前的实践指南建议对所有胸痛和LBBB患者进行溶栓治疗，但医生对出血性卒中的担忧使许多此类患者无法得到及时治疗。在一个未确定我们提出的心电图标准的LBBB和胸痛人群中，只有73%的符合条件的患者接受了溶栓治疗；另一方面，48%没有MI生化证据的患者接受了溶栓治疗。对于后一组患者而言，临床预测规则评分为0。相反，79%确诊为急性MI的患者预测规则评分≥2。类似的值适用于有系列心电图的患者亚组。我们建议，胸痛和LBBB患者的溶栓治疗应基于系统的心电图检查来决定，以“确诊患者”。这一措施可能会显著减少接受溶栓治疗但无梗死的患者数量，并使确实患有MI的患者得到及时治疗。
