ImportanceCurrent left bundle branch block (LBBB) criteria are based on animal experiments or mathematical models of cardiac tissue conduction and may misclassify patients. Improved criteria would impact referral decisions and device type for cardiac resynchronization therapy.ObjectiveTo develop a simple new criterion for LBBB based on electrophysiological studies of human patients, and then to validate this criterion in an independent population.Design, Setting, and ParticipantsIn this diagnostic study, the derivation cohort was from a single-center, prospective study of patients undergoing electrophysiological study from March 2016 through November 2019. The validation cohort was assembled by retrospectively reviewing medical records for patients from the same center who underwent transcatheter aortic valve replacement (TAVR) from October 2015 through May 2022.ExposuresPatients were classified as having LBBB or intraventricular conduction delay (IVCD) as assessed by intracardiac recording.Main Outcomes and MeasuresSensitivity and specificity of the electrocardiography (ECG) criteria assessed in patients with LBBB or IVCD.ResultsA total of 75 patients (median [IQR] age, 63 [53-70.5] years; 21 [28.0%] female) with baseline LBBB on 12-lead ECG underwent intracardiac recording of the left ventricular septum: 48 demonstrated complete conduction block (CCB) and 27 demonstrated intact Purkinje activation (IPA). Analysis of surface ECGs revealed that late notches in the QRS complexes of lateral leads were associated with CCB (40 of 48 patients [83.3%] with CCB vs 13 of 27 patients [48.1%] with IPA had a notch or slur in lead I; P = .003). Receiver operating characteristic curves for all septal and lateral leads were constructed, and lead I displayed the best performance with a time to notch longer than 75 milliseconds. Used in conjunction with the criteria for LBBB from the American College of Cardiology/American Heart Association/Heart Rhythm Society, this criterion had a sensitivity of 71% (95% CI, 56%-83%) and specificity of 74% (95% CI, 54%-89%) in the derivation population, contrasting with a sensitivity of 96% (95% CI, 86%-99%) and specificity of 33% (95% CI, 17%-54%) for the Strauss criteria. In an independent validation cohort of 46 patients (median [IQR] age, 78.5 [70-84] years; 21 [45.7%] female) undergoing TAVR with interval development of new LBBB, the time-to-notch criterion demonstrated a sensitivity of 87% (95% CI, 74%-95%). In the subset of 10 patients with preprocedural IVCD, the criterion correctly distinguished IVCD from LBBB in all cases. Application of the Strauss criteria performed similarly in the validation cohort.Conclusions and RelevanceThe findings suggest that time to notch longer than 75 milliseconds in lead I is a simple ECG criterion that, when used in conjunction with standard LBBB criteria, may improve specificity for identifying patients with LBBB from conduction block. This may help inform patient selection for cardiac resynchronization or conduction system pacing.

中文翻译：

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左束支阻滞的修订定义利用时间在导联 I 上切迹

重要性当前的左束支传导阻滞 (LBBB) 标准基于动物实验或心脏组织传导的数学模型，可能会对患者进行错误分类。改进的标准将影响心脏再同步治疗的转诊决策和设备类型。目的根据人类患者的电生理学研究制定一种简单的 LBBB 新标准，然后在独立人群中验证该标准。设计、设置和参与者在这项诊断研究中，衍生队列来自于 2016 年 3 月至 2019 年 11 月期间接受电生理学研究的患者的单中心前瞻性研究。验证队列是通过回顾性审查来自同一中心接受经导管主动脉瓣置换术 (TAVR) 的患者的医疗记录而组成的从 2015 年 10 月到 2022 年 5 月。暴露通过心内记录评估，患者被分类为 LBBB 或心室内传导延迟 (IVCD)。主要结果和措施评估 LBBB 或 IVCD 患者心电图 (ECG) 标准的敏感性和特异性。结果总计75 名患者（中位 [IQR] 年龄，63 [53-70.5] 岁； 21 名 [28.0%] 女性）在 12 导联心电图上出现基线 LBBB，接受了左心室间隔心内记录：48 名患者表现出完全传导阻滞 (CCB)，27 名患者表现出完整的浦肯野激活 (IPA)。表面心电图分析显示，侧导联 QRS 波群中的晚期切迹与 CCB 相关（48 名 CCB 患者中的 40 名 [83.3%]，而 27 名 IPA 患者中的 13 名 [48.1%] 在 I 导联上有切迹或模糊；磷=.003）。构建了所有间隔和侧导联的接受者操作特征曲线，导联 I 显示出最佳性能，切迹时间超过 75 毫秒。与美国心脏病学会/美国心脏协会/心律协会的 LBBB 标准结合使用，该标准的敏感性为 71%（95% CI，56%-83%），特异性为 74%（95%推导群体中的 CI，54%-89%），而 Strauss 的敏感性为 96%（95% CI，86%-99%），特异性为 33%（95% CI，17%-54%）标准。在一个由 46 名接受 TAVR 并间隔出现新 LBBB 的患者（中位 [IQR] 年龄，78.5 [70-84] 岁；21 名 [45.7%] 女性）组成的独立验证队列中，切迹时间标准的敏感性为87%（95% CI，74%-95%）。在 10 名术前 IVCD 患者的子集中，该标准在所有病例中都正确区分了 IVCD 和 LBBB。 Strauss 标准的应用在验证队列中的表现类似。结论和相关性研究结果表明，I 导联刻痕时间超过 75 毫秒是一个简单的 ECG 标准，当与标准 LBBB 标准结合使用时，可以提高识别患者的特异性与来自传导块的LBBB。这可能有助于告知患者选择心脏再同步或传导系统起搏。