The patient is a 67-year-old man with history of prostate cancer, diabetes mellitus and hyperlipidemia who was admitted to the hospital because of chest pain and a syncopal episode.
An ECG was performed:
The ECG shows which of the following:
The correct answer is: C. LBBB with concomitant lateral wall myocardial infarction (MI).
The patient has sinus rhythm with left bundle branch block (LBBB) with T vector consistent with LBBB. The ST and T waves are usually opposite in direction to QRS.1 Therefore typical ST segment in LBBB would be depressed in lead I and aVL. In our patient, the ST segment in lead I and aVL is elevated [red arrow] and concordant with QRS complex indicating lateral wall myocardial infarction (MI).
Diagnosis of acute MI in the presence of LBBB is challenging. Sgarbossa et al.2 recognized the following ECG criteria to diagnose MI in patients with LBBB including:
ST-elevation of ≥1 mm and concordant with the QRS complex
ST-segment depression ≥1 mm in lead V1, V2, or V3
ST elevation/S-wave amplitude of ≤ -0.253
The concordant ST elevation with QRS complex criterion has a specificity close to 98% but very low sensitivity at 20%. The absence of these criteria does not rule out MI.
Left heart catheterization showed high grade circumflex disease as well as 50-60% left main stenosis. He underwent coronary artery bypass graft.
Kusumoto FM, Schoenfeld MH, Barrett C, et al. 2018 ACC/AHA/HRS guideline on the evaluation and management of patients with bradycardia and cardiac conduction delay: a report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines and the Heart Rhythm Society. J Am Coll Cardiol 2018.
Sgarbossa EB, Pinski SL, Barbagelata A, et al. Electrocardiographic diagnosis of evolving acute myocardial infarction in the presence of left bundle-branch block. GUSTO-1 (Global Utilization of Streptokinase and Tissue Plasminogen Activator for Occluded Coronary Arteries) investigators. N Engl J Med 1996;334:481-7.
Smith SW, Dodd KW, Henry TD, Dvorak DM, Pearce LA. Diagnosis of ST-elevation myocardial infarction in the presence of left bundle branch block with ST-elevation to S-wave ratio in a modified Sgarbossa rule. Ann Emerg Med 2012;60:766-76.