European Journal of Cardiovascular Medicine

It can be challenging to diagnose acute myocardial infarction (AMI) on electrocardiograms in people who have left bundle branch block (LBBB). On the one hand, the majority of patients who are referred for primary percutaneous coronary intervention (pPCI) due to LBBB do not have an AMI. Conversely, patients with AMI and LBBB are typically at high risk and frequently encounter reperfusion therapy delays, which could have serious repercussions.

However, patients with LBBB cannot be diagnosed with AMI with certainty using even the most modern ECG algorithms. The LBBB pattern is distinguished in the absence of acute ischaemia by (1) ST-segment displacement in the opposite direction of the QRS complex polarity (also known as discordant ST deviation) and (2) the presence of some degree of proportionality between the voltage of the corresponding QRS complex and the magnitude of the discordant ST deviation. Therefore, in addition to the clinical signs of acute ischaemia, the presence of excessive discordant ST deviation (e.g., the ST/QRS ratio in the Modified Sgarbossa Criteria) and ST elevation concordant with QRS polarity (5 points in Sgarbossa rules) are specific for AMI. However, these criteria have a relatively low sensitivity.

There are two novel methods to increase the diagnostic sensitivity of ECG in individuals with LBBB and probable AMI. Second, since low-voltage QRS complexes often exhibit isoelectric ST-segment potentials in the absence of ischaemia, the presence of a significant (≥1 mm or 0.1 mV) discordant ST deviation in these complexes as a positive criterion for AMI. The optimal cutoff value for QRS voltage below which any discordant ST variation ≥1 mm (0.1 mV) would be considered excessive and indicative of AMI has not yet been investigated. Notably, because AMI is linked to lower QRS voltages in patients with LBBB, low-voltage QRS leads are frequently found in patients with both conditions.

The prospective observational study was conducted at the Shri B.M. Patil Medical college hospital and research center, Vijayapura during the period of Dec 2022 to Jan 2024. All consecutive patients referred for suspected myocardial infarction because of new or presumed new LBBB with available ECG recorded at the first medical contact were included in this study.   

Eligible participants who agreed to participate signed an informed written consent. The study was approved by an Institutional Ethics Committee (BLDE(DU)/IEC/845/2022-23).

The investigations which were carried out were electrocardiogram, troponin I. Investigation results are correlated with clinical probabilities.

Statistical methods:

The Statistical software namely SAS 9.2, SPSS 22.0, Stata 10.1, MedCalc 9.0.1, Systat 12.0 and R environment ver.2.11.1 were used for the analysis.

Continuous measurement results were presented as Mean SD (Min-Max), while categorical measurement results were presented as Number (percent). At the 5% level of significance, significance is determined. The significance of study parameters among three or more groups of patients has been determined using analysis of variance (ANOVA), Chi-square/ Fisher's exact test. The significance of study parameters on a categorical scale between two or more groups has been determined using the exact test.

A total of 39 patients were included. Mean age was 56.2 years, 23 were male (59%). The patients presented with symptoms of chest pain (48.7%), dyspnoea (17.9%) and palpitations (15.4%). The folowing comoridities were noted, diabetes in 51.3 % and hypertension in 43.6%. Median troponin I was 2197 pg/mL.

Table 1: Demographic profile, presenting symptoms and troponin I of patients (n=39)

Table 2: Barcelona criteria * TROPONIN I

Table 3: Modified Sgarbossa * TROPONIN I

Barcelona criteria had a sensitivity of 73 % and modified Sgarbossa had a sensitivity of 64%. Both the criteria had specificity of 100%.

The diagnosis of acute myocardial infarction (AMI) in patients with left bundle branch block (LBBB) presents significant challenges due to the obscured electrocardiographic (ECG) changes typically associated with AMI. Two prominent sets of criteria used to aid in this diagnostic process are the original Sgarbossa criteria and the modified Sgarbossa criteria, as well as the recently developed Barcelona criteria. This study intended to compare these criteria in terms of their diagnostic efficacy for AMI in the context of LBBB. The original Sgarbossa criteria, established in 1996, were designed to identify AMI in patients with LBBB by focusing on specific ST-segment deviations. These criteria include three main components: (1) ST-segment elevation of at least 1 mm in leads with a positive QRS complex, (2) ST-segment depression of at least 1 mm in lead V1, V2, or V3, and (3) ST-segment elevation of at least 5 mm in leads with a negative QRS complex ^[1]. However, the sensitivity of these criteria has been criticized, particularly in cases where the ST-segment changes are subtle or masked by the LBBB . In response to these limitations, the modified Sgarbossa criteria were introduced to enhance diagnostic accuracy. These criteria maintain the original framework but adjust the thresholds for ST-segment elevation and depression, allowing for greater sensitivity in detecting AMI in the presence of LBBB^[2]. Specifically, the modified criteria include a new component that considers the ratio of ST elevation to S-wave amplitude, which has been shown to improve diagnostic performance^[3,4]. Studies have validated the modified Sgarbossa criteria, indicating a higher sensitivity compared to the original criteria, thus making it a more reliable tool in clinical practice ^[5]. On the other hand, the Barcelona criteria were developed more recently with the aim of further improving diagnostic sensitivity in patients with LBBB. These criteria incorporate additional ECG findings and have demonstrated a sensitivity of up to 93% for diagnosing AMI, surpassing both the original and modified Sgarbossa criteria^[6]. The Barcelona criteria emphasize the importance of integrating clinical assessment and additional diagnostic modalities, such as echocardiography and biomarker testing, to enhance the overall diagnostic process ^[7]. Comparative studies have shown that while the modified Sgarbossa criteria provide a significant improvement over the original criteria, the Barcelona criteria may offer the best sensitivity and specificity for diagnosing AMI in patients with LBBB ^[8]. This is particularly relevant given that patients with LBBB often present with atypical symptoms, and the risk of misdiagnosis can lead to delays in necessary interventions ^[9]. In conclusion, while both the modified Sgarbossa and Barcelona criteria represent advancements in the diagnostic evaluation of AMI in the presence of LBBB, the Barcelona criteria appear to offer superior sensitivity and diagnostic accuracy ^[10]. Clinicians should consider utilizing these criteria in conjunction with comprehensive clinical assessments and additional diagnostic tools to ensure timely and accurate diagnosis of AMI in patients presenting with LBBB.

In 2 cohorts of patients with LBBB referred for pPCI, we identified and validated the new ECG algorithm. BARCELONA based on the presence of concordant ST deviation ≥1 mm (0.1 mV) in any ECG lead and/or discordant ST deviation ≥1 mm (0.1 mV) in leads with max (R|S) voltage ≤6 mm (0.6 mV). This algorithm significantly improved the diagnosis of AMI as compared with previous ECG rules, achieving a diagnostic performance for AMI similar to that of ECG in patients with-out LBBB. The high specificity of the algorithm was confirmed in a large and heterogeneous control group of patients without suspected AMI.

Prior Publication: Nil

Support: Nil

Conflict Of Interest: Nil

Permissions And Acknowledgement: Nil

1. Du, X. and Zhang, Y. (2022). Electrocardiographic diagnosis of acute myocardial infarction in a pacemaker patient: a case report. BMC Cardiovascular Disorders, 22. 10.1186/s12872-022-02462-7.
2. Theiling, B., Rezaie, S., & Smith, S. (2015). Validation of the modified sgarbossa criteria for acute coronary occlusion in the setting of left bundle branch block: a retrospective case-control study. American Heart Journal, 170(6), 1255-1264. 10.1016/j.ahj.2015.09.005.
3. Neeland, I., Kontos, M., & Lemos, J. (2012). Evolving considerations in the management of patients with left bundle branch block and suspected myocardial infarction. Journal of the American College of Cardiology, 60(2), 96-105.10.1016/j.jacc.2012.02.054
4. Smith, S., Dodd, K., Henry, T., Dvorak, D., & Pearce, L. (2012). Diagnosis of st-elevation myocardial infarction in the presence of left bundle branch block with the st-elevation to s-wave ratio in a modified sgarbossa rule. Annals of Emergency Medicine, 60(6), 766-776. 10.1016/j.annemergmed.2012.07.119
5. Sørensen, J., Stengaard, C., Sørensen, C., Thygesen, K., Bøtker, H., Thuesen, L., & Terkelsen, C. (2013). Diagnosis and outcome in a prehospital cohort of patients with bundle branch block and suspected acute myocardial infarction. European Heart Journal Acute Cardiovascular Care, 2(2), 176-181. 1177/2048872613483591
6. Venturin, C., Botton, D., Barcellos, B., Souza, F., Mendes, R., Costa, G., … & Moura, A. (2023). Especificidade e sensibilidade dos critérios de sgarbossa e barcelona no diagnóstico de infarto agudo do miocárdio na vigência de bloqueio de ramo esquerdo., 115-126. 10.47879/ed.ep.2023755p115
7. Mohammed Habib, (2024), Electrocardiographic Criteria for Diagnosis of Acute Myocardial Infarction in Patients with Left Bundle Branch Block, International Journal of Cardiovascular Medicine, 3(3); DOI:10.31579/2834-796X/061
8. Macfarlane PW. New ECG Criteria for Acute Myocardial Infarction in Patients With Left Bundle Branch Block. J Am Heart Assoc. 2020 Jul 21;9(14):e017119. doi: 10.1161/JAHA.120.017119. Epub 2020 Jul 4. PMID: 32627635; PMCID: PMC7660728.
9. Lindow T, Mokhtari A, Nyström A, Koul S, Smith SW, Ekelund U. Comparison of diagnostic accuracy of current left bundle branch block and ventricular pacing ECG criteria for detection of occlusion myocardial infarction. Int J Cardiol. 2024 Jan 15;395:131569. doi: 10.1016/j.ijcard.2023.131569. Epub 2023 Nov 4. PMID: 37931659.
10. Di Marco A, Rodriguez M, Cinca J, Bayes-Genis A, Ortiz-Perez JT, Ariza-Solé A, Sanchez-Salado JC, Sionis A, Rodriguez J, Toledano B, Codina P, Solé-González E, Masotti M, Gómez-Hospital JA, Cequier Á, Anguera I. New Electrocardiographic Algorithm for the Diagnosis of Acute Myocardial Infarction in Patients With Left Bundle Branch Block. J Am Heart Assoc. 2020 Jul 21;9(14):e015573. doi: 10.1161/JAHA.119.015573. Epub 2020 Jul 4. Erratum in: J Am Heart Assoc. 2020 Nov 17;9(22):e014618. doi: 10.1161/JAHA.119.014618. PMID: 32627643; PMCID: PMC7660719.