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Vectorcardiographic and electrocardiographic criteria to distinguish new and old left bundle branch block
Alexei Shvilkin1, Bosko Bojovic, Branislav Vajdic
1South Shore Hospital, South Weymouth, Massachusetts, USA.
Insights
New electrocardiogram (ECG) criteria can now differentiate new from old left bundle branch block (LBBB). This aids in managing patients with suspected acute coronary syndrome and LBBB.
Area of Science:
- Cardiology
- Medical Diagnostics
- Electrocardiography
Background:
- Differentiating new from old left bundle branch block (LBBB) lacks established criteria.
- This diagnostic gap complicates patient management, particularly those with suspected acute coronary syndrome.
Purpose of the Study:
- To develop novel electrocardiographic (ECG) criteria for distinguishing new-onset LBBB from old LBBB.
- To improve the diagnostic accuracy in identifying acute LBBB events.
Main Methods:
- Analysis of 3,706 LBBB electrocardiogram (ECG) tracings from a hospital database.
- Digital measurement of QRS and T-wave parameters and reconstruction of vectorcardiograms.
- Utilized receiver operator characteristic (ROC) curves to establish decision rules for differentiating LBBB types.
Main Results:
- New LBBB exhibited significantly larger T-vector magnitude and lower QRS/T vector magnitude ratio compared to old LBBB.
- The ratio of deepest S to largest T wave in precordial leads (Max S/T) was significantly smaller in new LBBB.
- A decision rule (QRS/T <2.25 and Max S/T <2.5) demonstrated 100% sensitivity and high specificity for diagnosing new LBBB.
Conclusions:
- The developed QRS/T and Max S/T criteria accurately discriminate between new and old LBBB.
- These criteria are suitable for both automated and manual ECG analysis.
- Prospective validation could enhance the management of chest pain patients with LBBB.
Background:
There are no established criteria to differentiate new from old left bundle branch block (LBBB). This complicates management of patients with LBBB and suspected acute coronary syndrome.
Objectives:
The purpose of this study was to develop electrocardiographic (ECG) criteria to differentiate new and old LBBB.
Methods:
All LBBB tracings (n = 3,706) in a hospital ECG database were retrieved. New (<24 hours, n = 39) and old (>24 hours, n = 1,760) LBBB tracings were identified. QRS and T-wave amplitudes, directions, and durations were measured digitally. Vectorcardiograms were reconstructed from 12-lead ECGs using inverse Dower transform and analyzed with Cardio3KG software. Receiver operator characteristic (ROC) curves were used to develop decision rules to distinguish new and old LBBB.
Results:
The new LBBB group had larger T-vector magnitude (1.20 +/- 0.07 vs. 0.71 +/- 0.01 mV), smaller QRS vector magnitude (2.13 +/- 0.12 vs. 2.47 +/- 0.02 mV), and a lower QRS/T vector magnitude ratio (QRS/T; 1.79 +/- 0.03 vs. 3.92 +/- 0.04) compared with the old LBBB group (mean +/- standard error of the mean, P <.001). The ratio of deepest S to largest T wave in precordial leads (Max S/T) was significantly smaller in the new compared with in the old LBBB group (1.66 +/- 0.05 vs. 3.54 +/- 0.08; P <.001). A decision rule using QRS/T <2.25 and Max S/T <2.5 had 100% sensitivity and 96%-68% specificity in diagnosing new LBBB, including subsets of patients with tachycardia and ischemia.
Conclusions:
QRS/T and Max S/T allow accurate discrimination between new and old LBBB suitable for both computerized and manual analysis. If confirmed in prospective studies, this finding can improve management of patients with chest pain and LBBB.
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