The first Department of Cardiology, the First Affiliated Hospital of Kunming Medical University, Kunming, Yunnan, China.
The third Department of Cardiology, the First Affiliated Hospital of Kunming Medical University, Kunming, Yunnan, China.
Int J Cardiol. 2024 May 1;402:131830. doi: 10.1016/j.ijcard.2024.131830. Epub 2024 Feb 4.
The existing ECG criteria for diagnosing left bundle branch block (LBBB) are insufficient to distinguish between true and false blocks accurately.
We hypothesized that the notch width of the QRS complex in the lateral leads (I, avL, V5, V6) on the LBBB-like ECG could further confirm the diagnosis of true complete left bundle branch block (t-LBBB). We conducted high-density, three-dimensional electroanatomical mapping in the cardiac chambers of 37 patients scheduled to undergo CRT. These patients' preoperative electrocardiograms met the ACC/AHA/HRS guidelines for the diagnosis of complete LBBB. If the left bundle branch potential could be mapped from the base of the heart to the apex on the left ventricular septum, it was defined as a false complete left bundle branch block (f-LBBB). Otherwise, it was categorized as a t-LBBB. We conducted a comparative analysis between the two groups, considering the clinical characteristics, real-time correspondence between the spread of ventricular electrical excitation and the QRS wave, QRS notch width of the lateral leads (I, avL, V5, V6), and the notch width/left ventricular end-diastolic diameter (Nw/LVd) ratio. We performed the ROC correlation analysis of Nw/LVd and t-LBBB to determine the sensitivity and specificity for diagnostic authenticity.
Twenty-five patients were included in the t-LBBB group, while 12 patients were assigned to the f-LBBB group. Within the t-LBBB group, the first peak of the QRS notch correlated with the depolarization of the right ventricle and septum, the trough corresponded to the depolarization of the left ventricle across the left ventricle, and the second peak aligned with the depolarization of the left ventricular free wall. In contrast, within the f-LBBB group, the first peak coincided with the depolarization of the right ventricle and a majority of the left ventricle, the second peak occurred due to the depolarization of the latest, locally-activated myocardium in the left ventricle, and the trough was a result of delayed activation of the left ventricle that did not align with the usual peak timing. The QRS notch width (45.2 ± 12.3 ms vs. 52.5 ± 9.2 ms, P < 0.05) and the Nw/LVd ratio (0.65 ± 0.19 ms/mm vs. 0.81 ± 0.17 ms/mm, P < 0.05) were compared between the two groups. After conducting the ROC correlation analysis, a sensitivity of 56% and a specificity of 91.7% for diagnosing t-LBBB using Nw/LVd were obtained.
By utilizing the current diagnostic criteria for LBBB, an increased Nw/LVd value can enhance the effectiveness of diagnosing LBBB.
现有的心电图诊断左束支传导阻滞（LBBB）的标准不足以准确区分真性和假性阻滞。
我们假设在类似 LBBB 的心电图的外侧导联（I、avL、V5、V6）中 QRS 复合波的切迹宽度可以进一步证实真性完全性左束支传导阻滞（t-LBBB）的诊断。我们对 37 名计划接受 CRT 的患者的心脏腔室进行了高密度、三维电解剖映射。这些患者的术前心电图符合 ACC/AHA/HRS 指南对完全性 LBBB 的诊断标准。如果可以从心脏底部在心室内隔的左侧将左束支电位映射到心尖，则定义为假性完全性左束支传导阻滞（f-LBBB）。否则，将其归类为 t-LBBB。我们对两组进行了对比分析，考虑了临床特征、心室电激动传播的实时对应关系、外侧导联（I、avL、V5、V6）的 QRS 切迹宽度以及切迹宽度/左心室舒张末期直径（Nw/LVd）比值。我们对 Nw/LVd 与 t-LBBB 进行了 ROC 相关分析，以确定诊断真实性的灵敏度和特异性。
25 名患者被纳入 t-LBBB 组，而 12 名患者被归入 f-LBBB 组。在 t-LBBB 组中，QRS 切迹的第一个峰与右心室和室间隔的去极化相对应，波谷对应于穿过左心室的左心室去极化，第二个峰与左心室游离壁的去极化相对应。相比之下，在 f-LBBB 组中，第一个峰与右心室和大部分左心室的去极化相对应，第二个峰是由于左心室最晚、局部激活的心肌去极化引起的，波谷是由于左心室延迟激活引起的，与通常的峰值时间不匹配。两组间 QRS 切迹宽度（45.2±12.3ms 比 52.5±9.2ms，P<0.05）和 Nw/LVd 比值（0.65±0.19ms/mm 比 0.81±0.17ms/mm，P<0.05）比较。通过 ROC 相关分析，Nw/LVd 诊断 t-LBBB 的灵敏度为 56%，特异性为 91.7%。
利用现有的 LBBB 诊断标准，增加 Nw/LVd 值可以提高 LBBB 的诊断效果。
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