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:
Figure 1
The ECG shows which of the following:
Show Answer
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).
Figure 2
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.
References
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.
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