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J Korean Soc Emerg Med > Volume 29(1); 2018 > Article
Journal of The Korean Society of Emergency Medicine 2018;29(1): 1-6.
좌각차단 환자에서 급성심근경색 진단을 위한 새로운 알고리듬
김동민, 오성범
단국대학교 의과대학 응급의학교실
The New Diagnostic Algorithm for New or Presumably New Left Bundle Branch Block and Suspected Acute Myocardial Infarction
Dong Min Kim, Seong Beom Oh
Department of Emergency Medicine, Dankook University College of Medicine, Cheonan, Korea
Correspondence  Seong Beom Oh ,Tel: 041-550-7241, Fax: 041-550-7054, Email: holytiger@hanmail.net,
Received: October 1, 2017; Revised: October 2, 2017   Accepted: October 26, 2017.  Published online: February 28, 2018.
Patients with a suspected acute myocardial infarction (AMI) in the setting of a new or presumably new left bundle branch block (LBBB) present an important diagnostic and therapeutic challenge to clinicians. This study was conducted to identify the frequency of ST-segment elevation myocardial infarction (STEMI)-equivalent in this population, determine the diagnostic value of electrocardiographic and echocardiographic features and propose a new diagnostic algorithm.
From 793 patients who underwent emergent coronary angiography between January 1, 2012 and July 31, 2015, we examined data pertaining to 21 patients with new or presumably new LBBB. These patients were classified into three groups: 1) STEMI-equivalent, defined as an acute coronary occlusion on coronary angiogram (six patients), 2) non-STEMI (NSTEMI) (six patients), and 3) diagnosis other than myocardial infarction (non-MI) (nine patients).
Six patients who met the ST-segment concordance criteria (score≥3) were STEMI-equivalent. On the other hand, seven patients with a discordant ST-elevation of ≥5 mm (score=2) were NSTEMI or non-MI. Therefore ST-segment concordance was highly sensitive and specific for the diagnosis of STEMI-equivalent. Compared with NSTEMI patients, nine non-MI patients with a normal angiogram had a low ejection fraction (35.6±19.0 vs. 56.0±12.9, p=0.04) and increased left ventricle end-diastolic dimension (63.9±8.8 vs. 51.7±6.4, p=0.012).
Only a minority of patients with LBBB and suspected AMI have a STEMI-equivalent. Low ejection fraction and increased end-diastolic dimension of left ventricle indicate normal coronary angiogram in patients without ST-segment concordance of Sgarbossa criteria. We propose a new modified diagnostic algorithm in this population.
Key words: Left bundle-branch block, Myocardial infarction, Echocardiography
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