Elias B Hanna1, Viral N Lathia2, Murtuza Ali3, Eliana Hanna Deschamps4. 1. Department of Medicine, Cardiovascular Section, Louisiana State University, New Orleans, LA, USA. Electronic address: ehanna@lsuhsc.edu. 2. Cardiovascular Section, University Medical Center, Lafayette, LA. 3. Department of Medicine, Cardiovascular Section, Louisiana State University, New Orleans, LA, USA. 4. Department of Medicine, University Hospital of Geneva, Geneva, Switzerland.
Abstract
BACKGROUND: In patients with suspected acute coronary syndrome, a new or presumably new left bundle branch block (LBBB) does not always imply ST-segment elevation myocardial infarction (STEMI). We aimed to show the low frequency of STEMI-equivalent in this population and determine the diagnostic value of electrocardiographic and echocardiographic features. METHODS: From the 387 patients captured by the Louisiana State University code STEMI registry between 2009 and 2012, we examined data on 26 patients with LBBB. These patients were divided into 3 groups according to the final diagnosis: (1) STEMI-equivalent, defined as an acute coronary occlusion on angiography (2 patients), (2) non-ST-segment elevation myocardial infarction (4 patients), and (3) diagnoses other than myocardial infarction (non-MI) (20 patients). RESULTS: Troponin elevation and left ventricular systolic dysfunction were common in all 3 groups (non-significant p-values). Compared with non-MI patients, patients with STEMI-equivalent had a larger degree of ST-segment discordance and T-wave discordance, as assessed by ST/QRS and T/QRS ratios (p<0.001). ST/QRS ratio ≥ 0.2 and T/QRS ratio ≥ 0.5 were sensitive and specific for the diagnosis of STEMI-equivalent in the setting of LBBB. Conversely, absolute values of ST-segment and T-wave discordance were not significantly different between groups. ST-segment concordance was highly specific for the diagnosis of STEMI-equivalent, but had a limited sensitivity. CONCLUSION: Only a minority of patients with suspected acute coronary syndrome and LBBB have a STEMI-equivalent. Excessive relative discordance of the ST segment or the T wave appears predictive of STEMI-equivalent, but this is only hypothesis-generating considering the small population size.
BACKGROUND: In patients with suspected acute coronary syndrome, a new or presumably new left bundle branch block (LBBB) does not always imply ST-segment elevation myocardial infarction (STEMI). We aimed to show the low frequency of STEMI-equivalent in this population and determine the diagnostic value of electrocardiographic and echocardiographic features. METHODS: From the 387 patients captured by the Louisiana State University code STEMI registry between 2009 and 2012, we examined data on 26 patients with LBBB. These patients were divided into 3 groups according to the final diagnosis: (1) STEMI-equivalent, defined as an acute coronary occlusion on angiography (2 patients), (2) non-ST-segment elevation myocardial infarction (4 patients), and (3) diagnoses other than myocardial infarction (non-MI) (20 patients). RESULTS: Troponin elevation and left ventricular systolic dysfunction were common in all 3 groups (non-significant p-values). Compared with non-MI patients, patients with STEMI-equivalent had a larger degree of ST-segment discordance and T-wave discordance, as assessed by ST/QRS and T/QRS ratios (p<0.001). ST/QRS ratio ≥ 0.2 and T/QRS ratio ≥ 0.5 were sensitive and specific for the diagnosis of STEMI-equivalent in the setting of LBBB. Conversely, absolute values of ST-segment and T-wave discordance were not significantly different between groups. ST-segment concordance was highly specific for the diagnosis of STEMI-equivalent, but had a limited sensitivity. CONCLUSION: Only a minority of patients with suspected acute coronary syndrome and LBBB have a STEMI-equivalent. Excessive relative discordance of the ST segment or the T wave appears predictive of STEMI-equivalent, but this is only hypothesis-generating considering the small population size.