Redefining left bundle branch block from high-density electroanatomical mapping

Area of Science:

• Cardiology
• Electrophysiology
• Medical Diagnostics

Background:

• Current electrocardiogram (ECG) criteria for diagnosing left bundle branch block (LBBB) are insufficient for accurate differentiation between true and false blocks.
• Distinguishing true LBBB from LBBB-like patterns is crucial for appropriate patient management and treatment, particularly in cardiac resynchronization therapy (CRT) candidates.

Purpose of the Study:

• To investigate the utility of QRS notch width in lateral leads as a supplementary diagnostic marker for true complete left bundle branch block (t-LBBB).
• To evaluate the diagnostic performance of the notch width to left ventricular end-diastolic diameter (Nw/LVd) ratio in differentiating t-LBBB from false LBBB (f-LBBB).

Main Methods:

• Utilized high-density, 3D electroanatomical mapping in 37 CRT patients with LBBB-like ECGs.
• Defined t-LBBB and f-LBBB based on the presence or absence of left bundle branch potentials from base to apex.
• Compared clinical characteristics, electrical excitation spread, QRS notch width, and Nw/LVd ratio between t-LBBB and f-LBBB groups.
• Performed ROC analysis to determine the sensitivity and specificity of Nw/LVd for diagnosing t-LBBB.

Main Results:

• Twenty-five patients were classified as t-LBBB and 12 as f-LBBB.
• Distinct patterns of QRS notch depolarization were observed between t-LBBB and f-LBBB groups.
• The Nw/LVd ratio showed a statistically significant difference between the groups (0.65 ± 0.19 ms/mm vs. 0.81 ± 0.17 ms/mm, P < 0.05).
• ROC analysis yielded a sensitivity of 56% and a specificity of 91.7% for diagnosing t-LBBB using the Nw/LVd ratio.

Conclusions:

• The Nw/LVd ratio serves as a valuable quantitative marker to enhance the diagnostic accuracy of LBBB.
• Incorporating the Nw/LVd measurement into existing ECG criteria can improve the identification of true LBBB.