Sensitive and specific criteria for the detection of acute myocardial infarction (AMI) in patients with left bundle branch block (LBBB) have eluded electrocardiographers for many years. The article by Di Marco et al in this issue of the Journal of the American Heart Association (JAHA)¹ suggests that enhanced criteria are a possibility. In 1996, Sgarbossa et al introduced new criteria for the diagnosis of AMI in LBBB purely on the basis of ST changes, with a sensitivity of 36%, a specificity of 96%, and a positive predictive value of 88%.² At the time, they represented a new approach, but they were enhanced later by Smith et al, whose modified Sgarbossa criteria³ had a sensitivity of 91% and a specificity of 90%, although the study group was somewhat small.³ A follow‐up case‐control study that assessed the same criteria produced results of 80% sensitivity and 99% specificity in 45 patients with an acute coronary occlusion and 249 controls.⁴ The modification of Smith et al³ was to replace one Sgarbossa criterion (STj ≥0.5 mV discordant with QRS) with a new criterion, namely |STj/Samp| ≥0.25 with STj ≥0.1 mV in the same lead.

In the article by Di Marco et al, the sensitivity and specificity in the test group of 107 patients were 93% and 94%, respectively.¹ This compares with 33% and 99% for the original Sgarbossa² criteria and 68% and 94% for the modified Sgarbossa criteria,^{3, 4} all based on the same test population of patients. Thus, the new approach represents a remarkable improvement in sensitivity, in particular compared with earlier approaches.

The authors chose a relatively conventional definition of LBBB with the QRS duration >0.12 seconds, QS or rS complex in V1, and an R wave peak time >60 ms in lead I, V5, or V6 along with the absence of a Q wave in these leads.¹ There was no requirement for notching or slurring of the R wave in I, V5, and V6 as in the long‐standing World Health Organization definition of LBBB.⁵ In 2009, an American Heart Association/American College of Cardiology Foundation/Heart Rhythm Society recommendations article⁶ produced a broader definition of LBBB, which stated that ST‐T waves are usually oppositely directed to the QRS complex, and positive T waves in the presence of an upright QRS complex may be normal. Subsequently, Strauss et al introduced a definition of strict LBBB with a QRS duration ≥130 ms in women and ≥140 ms in men.⁷ A QS or rS complex in V1 and V2, as well as notching or QRS slurring in mid‐QRS in ≥2 contiguous leads, completed their definition. They argued that many ECGs reported as showing LBBB had a wide QRS because of a combination of left ventricular hypertrophy and left anterior fascicular block and not LBBB. Their research was aimed at assessing the likelihood of success of cardiac resynchronization therapy, and hence they were using a strict definition of LBBB. Whether the definition of LBBB by Strauss et al⁷ would have altered results in the current study¹ is a question that cannot be answered here.

Figure 1 shows an example of LBBB in a 76‐year‐old woman. The reader is invited to review this ECG, and in the absence of any clinical details, consider the interpretation. Further discussion of this example will follow.

Does it show evidence of an acute myocardial infarction?

In the study of Di Marco et al,¹ all ECGs were interpreted visually by 2 cardiologists and there was an exceptionally high agreement between them (κ coefficient=0.98). Measurements >0.1 mV (1 mm) were made to the nearest 0.05 mV. This does raise the question that if ST amplitude, for example, happened to be bordering on 0.1 mV (eg, 0.095 mV), then it could have possibly influenced a cardiologist aware of a threshold of 0.1 mV. Of course, such a situation could affect both sensitivity and specificity, but it might mean that if automated methods were used for ECG interpretation of a new test set at some future point, the results of automated versus manual interpretation could differ.

The biggest difference between the new criteria and the original Sgarbossa criteria is that the new approach is not a point scoring system. The new criteria of Di Marco et al¹ have 2 major differences compared with previous criteria:

1. Although the Sgarbossa criteria used ST depression ≥0.1 mV as a criterion for AMI only in leads V1 to V3 with a dominant Q or S wave, the new approach extends this criterion to any lead (ie, where the ST depression and the QRS complex are “concordant”);

2. A completely new criterion, applicable in any lead, of ST deviation ≥0.1 mV, which is “discordant” with the QRS complex where the dominant QRS wave ≤0.6 mV (ie, the STj amplitude is oppositely directed to the dominant QRS deflection). Note that this is not peak to peak QRS amplitude.

Although the Sgarbossa criteria used ST depression ≥0.1 mV as a criterion for AMI only in leads V1 to V3 with a dominant Q or S wave, the new approach extends this criterion to any lead (ie, where the ST depression and the QRS complex are “concordant”);

A completely new criterion, applicable in any lead, of ST deviation ≥0.1 mV, which is “discordant” with the QRS complex where the dominant QRS wave ≤0.6 mV (ie, the STj amplitude is oppositely directed to the dominant QRS deflection). Note that this is not peak to peak QRS amplitude.

These 2 new criteria, together with an existing Sgarbossa criterion (namely, ST elevation ≥0.1 mV), which is concordant with the QRS complex, constitute the new so‐called Barcelona algorithm, which is positive if any 1 of the 3 above mentioned criteria is met.

The interesting new criterion is the use of a low‐voltage QRS complex together with ST deviation. It therefore is of some interest to consider the vectorcardiogram of LBBB, as shown in Figure 2.

The 3 planes of the VCG are transverse (T), frontal (T), and left sagittal (LS). The 3 orthogonal leads X, Y, and –Z, from which the VCG is constructed, are directed similarly to V6, aVF, and V2, respectively.

The classic LBBB pattern has a relatively narrow QRS loop and slow inscription signified by the close spacing of the dots that form the loop. In general terms, the T‐wave loop is oppositely directed from the QRS loop. Leads that are directed essentially parallel to the QRS loop, particularly in the transverse plane (eg, a precordial lead, such as lead V1 or V2), will have a high QRS voltage. Leads that are more directed at right angles to the VCG loop, such as V4 and V5 in this example, will have lower voltages because the component of the electrical activity in these leads is much less than in those leads directed similarly to the main QRS loop. It can be seen in Figure 2 that the voltage in V5 is less than one quarter of the voltage in V1. Thus, it can be expected that there will be a large variation in the amplitude of the QRS complex in ECGs with LBBB. This can also be seen in Figure 1 of the article by Di Marco et al.¹ There is therefore a small probability that evolving ST depression in the left lateral leads from V4, for example, toward V6 in an LBBB recorded from a patient without an AMI could therefore be associated with a low‐voltage QRS complex. This might account for the slightly reduced specificity of 94% in the new Barcelona criteria compared with 99% in the Sgarbossa criteria, but of course sensitivity is exceptionally high in the former at 93% compared with 33% in the latter.

ST depression in LBBB with a QRS amplitude ≤0.6 mV will undoubtedly occur in subjects without an AMI, possibly meeting the new Barcelona criterion of discordant ST deviation ≥0.1 mV. Of course, it is unrealistic to expect all criteria to be 100% specific! Sperry et al⁸ suggested that LBBB does not deter assessment of low‐QRS voltage in patients with cardiac amyloidosis, for example. Other well‐known causes of low voltage, such as chronic obstructive pulmonary disease, can occasionally occur in a patient with an LBBB.⁹ So, it would be unreasonable to expect any ECG criterion to be perfectly specific, but the Barcelona criteria do manage to marry a high specificity to a high sensitivity.

All the measurements in this study were made manually. In their supplementary data, the authors give an example where approximation of a measurement could lead to a different interpretation of one of the modified Sgarbossa criteria, depending on whether approximation of ST depression was 0.15 or 0.2 mV. This is because the ratio |STj/Samp| was involved. In the new Barcelona criteria, no ratios are involved. However, a similar situation must arise where the amplitude of an R or S wave could be 0.62 mV when measured by computer but a manual estimate measuring to the nearest 0.05 mV could be 0.6 mV. In the latter case, this wave would meet one of the Barcelona thresholds, being ≤0.6 mV, whereas the automated measurement would not. Of course, it could be argued development of the criteria is based on manual measurements and therefore application would also apply to manual measurements but clearly there is scope for variation here, as in any manual versus automated ECG measurement.

The authors performed a separate assessment of specificity on 214 hospital patients without any evidence of an AMI and who had not undergone cardiac catheterization. Specificity of the Barcelona criteria remained high at 90%, although this was the lowest specificity of all criteria.

Perhaps one of the most surprising aspects of the new criteria is the fact that discordant ST depression in V6, for example, can be regarded as a positive indicator of myocardial infarction if the R‐wave amplitude is ≤0.6 mV. This criterion had a surprisingly high specificity of 94%, even when assessed together with concordant ST elevation.

For this reason, the author made a rapid review of 50 cases of LBBB selected at random from a local database of several hundred thousand ECGs recorded mainly in a hospital setting. Time did not permit analysis of a larger sample. However, it was found that 94% of examples had a maximum R or S wave ≤0.6 mV in ≥1 lead. There is therefore scope for checking the new Barcelona criterion of significant discordant ST deviation.

It should also be noted that in Fig. 2, the R amplitude in V5 is approximately 0.5 mV and the STj depression exceeds 0.1 mV and so the Barcelona algorithm is positive.

With the above discussion in mind, the reader is encouraged to review again the ECG of Figure 1. Measurements quoted below were derived from automated analysis of the ECG using software from the author's laboratory.¹⁰

The leads of most interest are V2 and V4. The ST amplitude in V2 is 0.542 mV, meeting one of the Sgarbossa criteria, but this does not produce a score sufficient to report AMI. The S‐wave amplitude in V2 is 2.841 mV and so in this lead |STj/Samp|=0.19 and so the modified Sgarbossa criteria³ are not met. This criterion was not met in any other lead. The new Barcelona criterion of discordant ST deviation ≥0.1 mV is met in V4, where ST amplitude is 0.105 mV and the dominant S wave is 0.482 mV and hence ≤0.6 mV. In summary, this ECG should be reported as showing AMI according to the new Barcelona criteria.

Di Marco et al¹ point out that, in their cohort of patients referred for primary percutaneous coronary intervention, 63% unnecessarily underwent cardiac catheterization, no doubt in keeping with recommended guidelines, although the Sgarbossa criteria, with a specificity of 96%, were available, having been established in 1996. As the authors point out, the current European Society of Cardiology guidelines¹¹ advise that in a patient with a clinical suspicion of ongoing ischemic symptoms, an ECG showing LBBB should be regarded as an ST‐segment–elevation myocardial infarction equivalent, even if there was a previous ECG showing LBBB. These guidelines also emphasized that the presence of a (presumed) new LBBB does not predict a myocardial infarction. Nonetheless, if the new criteria can be externally validated, they could on occasion be a valuable aid in decision making.

The high sensitivity and specificity of the new Barcelona algorithm require to be assessed in an independent population, either manually or with automated techniques. It sometimes happens that criteria developed in one center do not perform so well when evaluated in another center. On the other hand, it could be argued that the established Sgarbossa criteria performed similarly in the Barcelona validation sample as in the original study.² Nevertheless, few ECG criteria have been shown through the years to be the order of 93% to 94% sensitive and specific and only time will tell whether the outstanding performance of the criteria set out in the article of Di Marco et al¹ will stand the test of independent assessment.

None.

多年来，心电图医师一直未能找到检测左束支传导阻滞 (LBBB) 患者急性心肌梗死 (AMI) 的敏感且具体的标准。 Di Marco 等人在本期美国心脏协会杂志( JAHA ) ¹上发表的文章表明，增强标准是可能的。 1996年，Sgarbossa等人提出了纯粹根据ST改变诊断LBBB AMI的新标准，其敏感性为36%，特异性为96%，阳性预测值为88%。 ²当时，它们代表了一种新方法，但后来被 Smith 等人增强，其修改后的 Sgarbossa 标准³的敏感性为 91%，特异性为 90%，尽管研究组规模较小。 ³一项评估相同标准的后续病例对照研究在 45 名急性冠状动脉闭塞患者和 249 名对照患者中得出了 80% 的敏感性和 99% 的特异性的结果。 ⁴ Smith 等人³的修改是用一个新标准取代一个 Sgarbossa 标准（STj ≥0.5 mV 与 QRS 不一致），即 |STj/Samp|同一导联中 ≥0.25，且 STj ≥0.1 mV。

在Di Marco等人的文章中，107名患者的测试组的敏感性和特异性分别为93%和94%。 ¹相比之下，原始 Sgarbossa ²标准为 33% 和 99%，修改后的 Sgarbossa 标准为 68% 和 94%， ^{3 、 4}均基于相同的患者测试人群。因此，新方法代表了灵敏度的显着提高，特别是与早期方法相比。

作者选择了相对传统的 LBBB 定义，其中 QRS 持续时间为 >0.12 秒，V1 中的 QS 或 rS 复合波，I、V5 或 V6 导联中的 R 波峰值时间为 >60 毫秒，并且没有 Q在这些线索中挥手。 ¹世界卫生组织对 LBBB 的长期定义中没有要求对 I、V5 和 V6 中的 R 波进行刻痕或模糊。 ⁵ 2009 年，美国心脏协会/美国心脏病学会基金会/心律协会建议第⁶条对 LBBB 提出了更广泛的定义，其中指出 ST-T 波通常与 QRS 波群相反，而正向 T 波位于 QRS 波群上。存在直立 QRS 波群可能是正常的。随后，Strauss 等人提出了严格的 LBBB 定义，即女性 QRS 时限≥130 ms，男性 QRS 时限≥140 ms。 ⁷ V1 和 V2 中的 QS 或 rS 复合波，以及 ≥2 个连续导联中 QRS 中段的切迹或 QRS 模糊，完成了他们的定义。他们认为，许多心电图报告显示 LBBB 具有宽 QRS，因为左心室肥大和左前束传导阻滞相结合，而不是 LBBB。他们的研究旨在评估心脏再同步治疗成功的可能性，因此他们使用了严格的 LBBB 定义。 Strauss 等人⁷的 LBBB 定义是否会改变当前研究¹的结果是一个此处无法回答的问题。

图 1 显示了一名 76 岁女性的 LBBB 示例。请读者查看此心电图，并在没有任何临床细节的情况下考虑解释。下面将对此示例进行进一步讨论。

它是否显示出急性心肌梗塞的证据？

在 Di Marco 等人的研究中， ¹所有心电图均由 2 名心脏病专家进行目视解读，他们之间的一致性极高（κ 系数 = 0.98）。测量值 >0.1 mV (1 mm) 精确到 0.05 mV。这确实提出了一个问题，例如，如果 ST 幅度​​恰好接近 0.1 mV（例如 0.095 mV），那么它可能会影响心脏病专家意识到 0.1 mV 的阈值。当然，这种情况可能会影响敏感性和特异性，但这可能意味着，如果在未来某个时刻使用自动化方法对新测试集进行心电图解释，则自动与手动解释的结果可能会有所不同。

新标准与原Sgarbossa标准的最大区别在于，新方法不是积分系统。 Di Marco等人¹的新标准与之前的标准相比有2个主要区别：

1. 
   尽管 Sgarbossa 标准仅在具有 Q 波或 S 波主导的 V1 至 V3 导联中使用 ST 压低 ≥0.1 mV 作为 AMI 的标准，但新方法将该标准扩展到任何导联（即，ST 压低和 QRS 复合波在导联中） “一致”）；

2. 
   适用于任何导联的全新标准，ST 偏差≥0.1 mV，与 QRS 复合波“不一致”，其中主导 QRS 波≤0.6 mV（即 STj 幅度与主导 QRS 偏转方向相反）。请注意，这不是 QRS 波幅的峰峰值。

尽管 Sgarbossa 标准仅在具有 Q 波或 S 波主导的 V1 至 V3 导联中使用 ST 压低 ≥0.1 mV 作为 AMI 的标准，但新方法将该标准扩展到任何导联（即，ST 压低和 QRS 复合波在导联中） “一致”）；

适用于任何导联的全新标准，ST 偏差≥0.1 mV，与 QRS 复合波“不一致”，其中主导 QRS 波≤0.6 mV（即 STj 幅度与主导 QRS 偏转方向相反）。请注意，这不是 QRS 波幅的峰峰值。

这两个新标准与现有的与 QRS 波群一致的 Sgarbossa 标准（即 ST 段抬高≥0.1 mV）一起构成了新的所谓的巴塞罗那算法，如果上述 3 个标准中的任何一个满足，则该算法为阳性已满足。

有趣的新标准是结合使用低电压 QRS 波群和 ST 偏差。因此，考虑 LBBB 的心向量图是有意义的，如图 2 所示。

VCG 的 3 个平面是横切面 (T)、额切面 (T) 和左矢状面 (LS)。构建 VCG 的 3 个正交导联 X、Y 和 –Z 的方向分别与 V6、aVF 和 V2 类似。

经典的 LBBB 模式具有相对较窄的 QRS 环和缓慢的铭文，这通过形成环的点间距很近来表示。一般来说，T 波环路与 QRS 环路方向相反。基本上平行于QRS环定向的导联，特别是在横向平面中的导联（例如，心前导联，诸如导联V1或V2）将具有高QRS电压。与 VCG 环路更成直角的导联（例如本例中的 V4 和 V5）将具有较低的电压，因为这些导联中的电活动分量比与主 QRS 环路类似的导联中的电活动分量少得多。从图2中可以看出，V5中的电压小于V1中电压的四分之一。因此，可以预期 LBBB 心电图中 QRS 波幅会有很大的变化。这也可以从 Di Marco 等人文章的图 1 中看出。 ¹因此，在没有 AMI 的患者记录的 LBBB 中，左侧导联从 V4 发展到 V6 的 ST 压低的可能性很小，因此可能与低电压 QRS 波群相关。这可能是新巴塞罗那标准中 94% 的特异性与 Sgarbossa 标准中的 99% 相比略有下降的原因，但当然，前者的敏感性异常高，为 93%，而后者为 33%。

LBBB 中 QRS 波幅≤0.6 mV 的 ST 压低无疑会发生在没有 AMI 的受试者中，可能符合新的巴塞罗那标准，即 ST 偏差≥0.1 mV。当然，期望所有标准 100% 具体是不现实的！例如，Sperry 等人⁸认为 LBBB 并不妨碍对心脏淀粉样变性患者的低 QRS 电压进行评估。其他众所周知的低电压原因，例如慢性阻塞性肺疾病，偶尔也会发生在 LBBB 患者身上。 ⁹因此，期望任何心电图标准完全具体是不合理的，但巴塞罗那标准确实设法将高特异性与高敏感性结合起来。

本研究中的所有测量都是手动进行的。在补充数据中，作者给出了一个例子，其中测量的近似值可能会导致对修改后的 Sgarbossa 标准之一的不同解释，具体取决于 ST 压低的近似值是 0.15 还是 0.2 mV。这是因为比率 |STj/Samp|参与其中。在巴塞罗那的新标准中，不涉及任何比率。然而，一定会出现类似的情况，即计算机测量时 R 波或 S 波的幅度可能为 0.62 mV，但手动估计测量到最接近的 0.05 mV 可能为 0.6 mV。在后一种情况下，该波将满足巴塞罗那阈值之一，≤0.6 mV，而自动测量则不会。当然，可以说标准的制定是基于手动测量，因此应用程序也适用于手动测量，但显然这里存在变化的范围，就像任何手动与自动心电图测量一样。

作者对 214 名没有任何 AMI 证据且未接受心导管插入术的医院患者进行了单独的特异性评估。巴塞罗那标准的特异性仍高达 90%，尽管这是所有标准中特异性最低的。

也许新标准最令人惊讶的方面之一是，例如，如果 R 波幅度≤0.6 mV，V6 中不一致的 ST 压低可以被视为心肌梗塞的阳性指标。即使与一致的 ST 抬高一起评估，该标准的特异性也高达 94%，令人惊讶。

为此，作者从本地数据库中随机抽取的 50 例 LBBB 病例进行了快速回顾，该数据库主要在医院环境中记录了数十万个心电图。时间不允许分析更大的样本。然而，我们发现 94% 的示例在 ≥1 导联中的最大 R 波或 S 波≤0.6 mV。因此，存在检查新的巴塞罗那显着不一致 ST 偏差标准的余地。

还应该注意的是，在图 2 中，V5 中的 R 幅度约为 0.5 mV，STj 压低超过 0.1 mV，因此巴塞罗那算法为正。

考虑到上述讨论，鼓励读者再次查看图 1 的心电图。下面引用的测量结果是使用作者实验室的软件对心电图进行自动分析得出的。 ¹⁰

最感兴趣的线索是 V2 和 V4。 V2 中的 ST 幅度​​为 0.542 mV，满足 Sgarbossa 标准之一，但这不会产生足以报告 AMI 的分数。 V2 中的 S 波幅度为 2.841 mV，因此在此导联中 |STj/Samp|=0.19，因此不满足修改后的 Sgarbossa 标准³ 。任何其他线索均未满足此标准。 V4 满足新的巴塞罗那标准不一致 ST 偏差 ≥0.1 mV，其中 ST 幅度​​为 0.105 mV，主导 S 波为 0.482 mV，因此≤0.6 mV。总之，根据新的巴塞罗那标准，该心电图应报告为显示 AMI。

Di Marco 等人¹指出，在转诊进行直接经皮冠状动脉介入治疗的患者队列中，63% 的患者不必要地接受了心导管插入术，这无疑符合推荐的指南，尽管可以使用特异性为 96% 的 Sgarbossa 标准，于 1996 年建立。正如作者指出的，当前的欧洲心脏病学会指南¹¹建议，对于临床怀疑持续缺血症状的患者，心电图显示 LBBB 应被视为 ST 段抬高心肌。即使之前的心电图显示 LBBB，也相当于梗塞。这些指南还强调，（假定的）新 LBBB 的存在并不能预测心肌梗死。尽管如此，如果新标准能够得到外部验证，它们有时可以为决策提供宝贵的帮助。

新巴塞罗那算法的高灵敏度和特异性需要在独立群体中进行评估，无论是手动还是自动化技术。有时，一个中心制定的标准在另一中心进行评估时表现不佳。另一方面，可以说，既定的 Sgarbossa 标准在巴塞罗那验证样本中的表现与原始研究中相似。 ²然而，多年来，很少有心电图标准被证明具有 93% 至 94% 的敏感度和特异性，只有时间才能证明 Di Marco 等人¹的文章中提出的标准的出色表现是否会持续下去。独立评估测试。

 没有任何。