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Comparison of the QRS Complex, ST-Segment, and T-Wave Among Patients with Left Bundle Branch Block with and without
Kenneth W Dodd1, Kendra D Elm2, Stephen W Smith2
1Department of Emergency Medicine, Hennepin County Medical Center, Minneapolis, Minnesota; Department of Internal Medicine, Hennepin County Medical Center, Minneapolis, Minnesota.
Insights
This study compared diagnostic criteria for acute coronary occlusion (ACO) in left bundle branch block (LBBB) patients. While differences were found, none surpassed the modified Sgarbossa criteria for ACO diagnosis.
Area of Science:
- Cardiology
- Diagnostic Imaging
- Emergency Medicine
Background:
- Modified Sgarbossa criteria are validated for diagnosing acute coronary occlusion (ACO) in left bundle branch block (LBBB).
- Previous studies lacked analysis of specific QRS, T-wave, and ST-segment concordance variations (< 1 mm).
- No comparative analysis existed for patients with acute myocardial infarction (AMI) without ACO (non-STEMI) versus those with ACO or no MI.
Purpose of the Study:
- To compare QRS amplitude, ST-segment morphology, ST-concordance (< 1 mm), and T-waves in LBBB patients with ACO, non-STEMI, and no MI.
- To evaluate the diagnostic utility of these specific ECG findings in differentiating these patient groups.
Main Methods:
- Retrospective analysis of emergency department patients with LBBB and ischemic symptoms.
- Patient groups included those with no MI, angiographically proven ACO, and non-STEMI.
- Comparison of ECG parameters such as QRS amplitude (ΣQRS), ST-segment morphology, ST-concordance, and T-wave concordance.
Main Results:
- Sum of QRS amplitude (ΣQRS) was smaller in ACO patients (101.5 mm) versus non-ACO (132.5 mm), with ΣQRS < 90 mm showing 92% specificity for ACO.
- Non-concave ST-segment morphology (91% specific) and ST-concordance ≥ 1 mm (95% specific) were highly specific for ACO.
- Terminal T-wave concordance showed moderate sensitivity (79%) for non-STEMI.
Conclusions:
- Distinct differences in QRS amplitude, ST-segment morphology, and T-waves exist between LBBB patients with ACO, non-STEMI, and no MI.
- However, none of the evaluated individual criteria demonstrated superior diagnostic performance compared to the modified Sgarbossa criteria for ACO in LBBB.
- Further research may explore combinations of these ECG findings for improved diagnostic accuracy.
Background:
The modified Sgarbossa criteria have been validated as a rule for diagnosis of acute coronary occlusion (ACO) in left bundle branch block (LBBB). However, no analysis has been done on differences in the QRS complex, T-wave, or ST-segment concordance of < 1 mm in the derivation or validation studies. Furthermore, there was no comparison of patients with acute myocardial infarction (AMI) but without ACO (i.e., non-ST-elevation myocardial infarction [non-STEMI]) to patients with ACO or without AMI (no MI).
Objective:
We compare findings involving the QRS amplitude, ST-segment morphology, ST-concordance < 1 mm, and T-waves in patients with LBBB with ACO, non-STEMI, and no MI.
Methods:
Retrospectively, emergency department patients were identified with LBBB and ischemic symptoms but no MI, with angiographically proven ACO, and with non-STEMI.
Results:
ACO, non-STEMI, and no MI groups consisted of 33, 24, and 105 patients. The sum of the maximum deflection of the QRS amplitude across all leads (ΣQRS) was smaller in patients with ACO than those without ACO (101.5 mm vs. 132.5 mm; p < 0.0001) and a cutoff of ΣQRS < 90 mm was 92% specific. For ACO, non-concave ST-segment morphology was 91% specific, any ST concordance ≥ 1 mm was 95% specific, and any ST concordance ≥ 0.5 mm was 94% sensitive. For non-STEMI, terminal T-wave concordance, analogous to biphasic T-waves, was moderately sensitive at 79%.
Conclusions:
We found differences in QRS amplitude, ST-segment morphology, and T-waves between patients with LBBB and ACO, non-STEMI, and no MI. However, none of these criteria outperformed the modified Sgarbossa criteria for diagnosis of ACO in LBBB.
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