As a review summarized, “not only is the ECG diagnosis of AMI difficult due to ‘masking’ of characteristic ECG changes by altered ventricular depolarization, but these patients may be at higher risk for AMI, congestive heart failure, and death compared with patients without BBB.” The first guidelines treated all patients with ischemic symptoms and LBBB as STEMI, based on early trials. Then the guidelines shifted consider “new LBBB” as STEMI equivalents, based on the assumption it takes a large anterior infarct to block both left fascicles. But most LBBB are not caused by acute ischemia but by chronic heart disease, which is a risk factor for ACS but not an automatic indication for reperfusion therapy. Patients presenting to the ED with ischemic symptoms have similar rates of MI whether they have new LBBB, old LBBB or no LBBB . Treating “new LBBB” as STEMIs led to unnecessary interventions, so this indication was removed from the 2013 AHA guidelines. But this leads to the opposite problem: “the guidelines fail to recognize that some patients with suspected ischemia and LBBB do have STEMI, and denying reperfusion therapy could be fatal.”
STEMI描述ST段抬高在两个连续的线索，但Sgarbossa确定了急性再灌注，包含在一个铅STE一致抬高或压低标准。但条件是基于酶的诊断AMI，有一个复杂的评分系统，并具有灵敏度不足和特异性（部分地是因为不成比例STE的标准是基于绝对值而不管前述QRS的大小）。史密斯研究血管造影确诊罪犯病变，并确定心电图标准，可以预测闭塞MI，从STEMI范例移离和添加诊断准确性到Sgarbossa标准。了Smith-改性Sgarbossa标准replaced the absolute discordance of >5mm with a relative discordance of ST/S<-0.25 (i.e. amplitude of STE greater than 25% of the amplitude of the preceding S wave), and also included any excessive discordance (either STE >30% the preceding S wave, or STD>30% preceding R wave ) in any lead .
从STEMI到OMI移位（闭塞MI）包括检查相对于前述QRS和在病人的症状上下文ST的变化（既仰角和俯角）。作为验证研究发现，“我们发现，修改后的Sgarbossa标准进行同样很好用的-0.20 -0.25或者一个比例截止。正如预期的那样，然而，-0.20的截止产生了比-0.25截止（84％比80％）略微更高的灵敏度和略低的特异性（94％比99％）。因此，使用-0.20 -0.25或者作为比例不一致的决定也不是绝对的，而是依赖于医生的预测概率和临床方面。心电图应该总是在临床背景中使用，作为诊断ST段抬高是在ACO经常不存在，即使在正常传导（即，无束支传导阻滞）。” 蔡（以下引用）提出了一种算法，该算法考虑到Sgarbossa/Smith criteria, but that starts with the patient’s clinical status. As with refractory ischemia or hemodynamically unstable patients with normal conduction, the 2017 European guidelines emphasize that “patients with a clinical suspicion of ongoing myocardial ischaemia and LBBB should be managed in a way similar to STEMI patients, regardless of whether the LBBB is previously known…Suspicion of ongoing myocardial ischaemia is an indication for a primary PCI strategy even in patients without diagnostic ST-segment elevation.”
NSR与LBBB解释通过心脏病学“正Sgarbossa标准具有>5毫米STE在V2-3”（其将指示可能LAD闭塞）。但在V2-3的STE正比于大规模的QRS波群：STE / S在V2 = 6/43 = 0.14，V3 =53分之6= 0.11。There are no modified-Sgarbossa criteria for occlusion MI, but patient had ongoing chest pain with a positive trop requiring cath lab activation, which found a circumflex occlusion (which doesn’t meet STEMI criteria in a quarter of the cases even in patients without LBBB).