The New Diagnostic Algorithm for New or Presumably New Left Bundle Branch Block and Suspected Acute Myocardial Infarction

Kim, Dong Min; Oh, Seong Beom

Abstract

PURPOSE
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.
METHODS
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).
RESULTS
Six patients who met the ST-segment concordance criteria (scoreâ‰¥3) were STEMI-equivalent. On the other hand, seven patients with a discordant ST-elevation of â‰¥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).
CONCLUSION
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.