A 39-year-old male patient presented to our emergency department with complaints of chest discomfort for the past 6 hours. His chest pain was a dull aching type, retrosternal, and was not radiating elsewhere. He was diagnosed with systemic hypertension 1 year back and was on regular medication since then. A 12-lead ECG was taken, which is shown in Figure 1. What is the electrocardiographic diagnosis?

Figure 1. Twelve-lead ECG at presentation.

Please turn the page to read the diagnosis.

The 12-lead ECG of the patient showed a normal sinus rhythm with a heart rate of 81 beats per minute and a normal axis. The 12-lead ECG also showed diffuse ST depression in leads I, II, aVL, aVF, V5, and V6, and ST elevation in lead aVR. Along with these findings, there were also abnormal T waves with bizarre morphology in leads I, II, aVL, aVR, aVF, V5, and V6. One typical pattern observed in the 12-lead ECG is that all the limb leads except lead III showed this bizarre morphology of ST-segment and T waves. These bizarre morphologies of ST-segments and T waves are generally known as electromechanical association (EMA) artifact.

An EMA artifact is a “heart-made” artifact caused by arterial pulsations or precordial pulsations at the site where the limb leads or chest leads are placed. An artifact in the ECG can be classified into heart-made and “non–heart-made.” In heart-made artifacts, the artifactual waves synchronize with the cardiac rhythm. This makes the heart-made artifacts difficult to interpret. In a non–heart-made artifact, the artifactual waves do not synchronize with the cardiac rhythm, and hence these artifactual waves will be separated at some point and can be distinguished easily (Figure 2). The most common sources of non–heart-made artifacts are the limb leads, because there may be limb movements, misplacement of leads, or loose connections.¹

Figure 2. Two different types of artifacts. EMA indicates electromechanical association.

The EMA artifact is a result of the transmission of arterial pulsations (usually radial artery) onto the lead clips producing the artifact. Modern machines only record lead I and lead II and derive the waveforms for the rest of the leads from these 2 leads.² Hence, most of the limb leads and augmented leads will be affected. However, in an EMA artifact, almost always, 1 lead will be spared depending on the limb that produces the artifact. This is the most important clue for diagnosing an EMA artifact. An EMA artifact will almost always spare 1 limb lead, depending on the limb from which artifacts are generated.

In our patient, lead III is spared. Because lead III is an ECG recording between the left arm and left leg with the positive pole being kept in the left arm and the negative pole being kept in the left leg, both these limbs are spared. Hence, the source of the artifact for our patient will be the right arm. A repeat ECG was done with the clip placed proximally (Figure 3). This 12-lead ECG did not show any artifacts. Because of our case, we emphasize that conditions that mimic acute coronary syndrome like hyperkalemia and artifacts will lead to unnecessary invasive investigations if not recognized.

Figure 3. Twelve-lead ECG taken after 15 minutes with the right arm clip placed proximally.

The key learning points are (1) EMA artifacts can mimic acute coronary syndrome, (2) EMA artifacts are heart-made and hence difficult to recognize as an artifact, (3) the clue to diagnosing an EMA artifact is that it almost always spares one of the limb leads, and (4) failure to recognize this artifact can lead to unnecessary invasive interventions.

The authors thank Dr Balasubramaniyam, Dr Raja Selvaraj, Dr Anandharaja, and Dr Sathish L for ECG lessons through a state-level monthly ECG club.

None.

Disclosures None.

For Sources of Funding and Disclosures, see page 753.

https://www.ahajournals.org/journal/circ

一名 39 岁男性患者在过去 6 小时内因胸部不适主诉到我们的急诊科就诊。他的胸痛是一种钝痛，胸骨后疼痛，没有放射到其他地方。他在 1 年前被诊断出患有系统性高血压，此后一直在接受常规药物治疗。做了12导联心电图，如图1所示，心电图诊断是什么？

图 1. 演示中的 12 导联心电图。

请翻页阅读诊断。

患者12导联心电图显示窦性心律正常，心率81次/分，电轴正常。12 导联心电图还显示 I、II、aVL、aVF、V5 和 V6 导联弥漫性 ST 段压低，aVR 导联 ST 段抬高。除了这些发现外，在 I、II、aVL、aVR、aVF、V5 和 V6 导联中也有异常形态的异常 T 波。在 12 导联心电图中观察到的一种典型模式是，除 III 导联之外的所有肢体导联都显示出这种奇异的 ST 段和 T 波形态。ST 段和 T 波的这些奇异形态通常被称为机电关联 (EMA) 伪影。

EMA 伪影是由动脉搏动或心前区搏动在放置肢体导联或胸导联的部位引起的“心脏制造”伪影。心电图中的伪影可分为心脏制造的和“非心脏制造的”。在心脏人工制品中，人工波与心律同步。这使得心脏制造的文物难以解释。在非心脏人工伪影中，人为波与心律不同步，因此这些人为波会在某些时候分离，很容易区分（图 2）。非心脏人工制品的最常见来源是肢体导线，因为可能存在肢体运动、导线错位或连接松动。¹

图 2. 两种不同类型的工件。EMA 表示机电关联。

EMA 伪影是动脉搏动（通常是桡动脉）传输到产生伪影的导线夹上的结果。现代机器仅记录导联 I 和导联 II，并从这 2 个导联导出其余导联的波形。²因此，大部分肢体导联和增强导联都会受到影响。然而，在 EMA 伪影中，根据产生伪影的肢体，几乎总是会保留 1 个导联。这是诊断 EMA 伪影的最重要线索。EMA 伪影几乎总是保留 1 个肢体导联，具体取决于生成伪影的肢体。

在我们的患者中，III 导联没有受到影响。由于III导联是左臂和左腿之间的心电图记录，正极保留在左臂，负极保留在左腿，因此这两条腿都没有受到影响。因此，我们患者的工件来源将是右臂。将夹子置于近端进行重复 ECG（图 3）。该 12 导联心电图未显示任何伪影。由于我们的案例，我们强调模拟急性冠状动脉综合征的情况，如高钾血症和伪影，如果不被识别，将导致不必要的侵入性检查。

图 3. 15 分钟后拍摄的 12 导联心电图，右臂夹置于近端。

关键学习点是 (1) EMA 伪影可以模仿急性冠状动脉综合征，(2) EMA 伪影是心脏制造的，因此难以识别为伪影，(3) 诊断 EMA 伪影的线索是它几乎总是会幸免于难一根肢体导联，以及 (4) 未能识别该伪影可能会导致不必要的侵入性干预。

作者感谢 Balasubramaniyam 博士、Raja Selvaraj 博士、Anandharaja 博士和 Sathish L 博士通过州级每月心电图俱乐部提供心电图课程。

没有任何。

披露无。

有关资金来源和披露信息，请参见第 753 页。

https://www.ahajournals.org/journal/circ