Evaluation of T-Wave Morphology in Patients With Left Bundle Branch Block and Suspected Acute Coronary Syndrome.

Abstract

T-wave morphology in the setting of left bundle branch block (LBBB) has been proposed as an indicator of myocardial ischemia.We sought to identify T-wave morphology findings in patients with LBBB that predict non-ST-segment elevation myocardial infarction (NSTEMI). We hypothesized that two or more contiguous leads with concordant T waves would be predictive of NSTEMI.This was a retrospective cohort study performed by chart review in a tertiary care center emergency department. We identified a consecutive cohort who presented with LBBB and symptoms consistent with acute coronary syndrome. Exclusion criteria were diastolic blood pressure > 120 mm Hg, heart rate > 130 beats/min, positive pressure ventilation, potassium > 5.5 mEq/L, and cardiac arrest without prearrest electrocardiogram (ECG) available. We collected ECGs and classified T waves into five categories based on morphology, blinded to clinical outcome. Clinical outcome data were collected blinded to ECG findings. Those with ECG diagnostic of STEMI by modified Sgarbossa criteria were excluded from the primary analysis, which was sensitivity and specificity of two or more contiguous leads with concordant T waves for NSTEMI.There were 246 patients included. Mean age was 73 years; 160 (65%) were female, and 32 had myocardial infarction. Thirty percent had two or more contiguous precordial leads with partially or completely concordant T waves. For NSTEMI, the sensitivity and specificity of this finding were 19% (95% confidence interval [CI] 8-37) and 68% (95% CI 61-74).We found no clinically useful relationship between T-wave concordance and myocardial infarction in our patient population. Future investigation of LBBB T-wave morphology should focus on alternative populations and findings.