114 T-Wave Changes Aid in the Electrocardiographic Diagnosis of Acute Coronary Occlusion in Left Bundle Branch Block

In patients with acute myocardial infarction (MI) and normal cardiac conduction, T-wave changes such as hyperacute T-waves and T-wave inversion are known to occur. Here we investigate T-wave changes in patients with left bundle branch block (LBBB) and acute coronary occlusion (ACO), including absolute T-wave amplitude (TWA), discordant TWA-to-QRS amplitude ratio (TWA/QRS), and concordant ST-segment deviation-to-TWA ratio (ST/TWA). We hypothesize that these parameters will be greater in LBBB patients with ACO than in those without ACO. Retrospectively, ECGs of ED patients with LBBB and ischemic symptoms were obtained. The ACO (“STEMI”-equivalent) group patients had 1) angiographically proven ACO or 2) culprit lesion and troponin I ≥ 10 ng/ml. The non-ACO control group consisted of patients with either 1) serial troponin-I below the 99% upper reference limit of the assay (“no-MI” subgroup) or 2) elevated troponin-I but negative emergent coronary angiography or echocardiography (“non-STEMI” subgroup). ECG measurements included S- or R-wave amplitude, ST deviation at the J point, and TWA to the nearest 0.5 mm relative to the PQ junction. Concordance and discordance were incorporated due to the importance of this principle in LBBB; they were defined in relation to the ST segment for the ST/TWA ratio and QRS complex for the TWA/QRS ratio. The maximum ratio of all 12 leads in a given ECG was used in calculations. Statistics were by Kruskal-Wallis test or McNemar’s test and are reported with interquartile range [IQR] or 95% confidence interval (95% CI) as appropriate. There were 33 patients in the ACO group and 129 patients in the non-ACO group. Of the 129 non-ACO patients, 105 had no-MI and 24 met criteria for non-STEMI. The median TWA was 9 mm [IQR 6.5-11] for ACO and 8.5 mm [IQR 6.5-11.5] for no-ACO patients (p = NS). The TWA/QRS ratio was significantly larger for ACO versus no-ACO patients (p < 0.05; see Table). For ACO, the specificity of any TWA/QRS > 1.25 was 93% (95% CI 87-97) and the sensitivity was 45% (95% CI 29-63). Subgroup analysis of TWA and TWA/QRS ratio in non-STEMI versus no-MI patients was not significant. Similarly, the ST/TWA ratio was significantly increased for ACO versus no-ACO patients but not for non-STEMI patients compared to no-MI patients (Table). For ACO, any ST/TWA > 0.80 had a sensitivity and specificity of 76% (95% CI 57-88) and 59% (95% CI 50-67), respectively. We found that patients with LBBB and ACO have proportionally larger T-waves (ie, higher TWA/QRS ratios) compared to no-ACO patients with LBBB. A cutoff of TWA/QRS > 1.25 has high specificity for ACO in LBBB. This may be analogous to hyperacute T-waves in STEMI in normal conduction. Additionally, the concordant ST/TWA ratio is significantly increased in ACO in LBBB. Further studies to define T-wave changes in patients with LBBB and ACO are needed and the diagnostic potential of these findings should be assessed.TableT-Wave Ratios in LBBBMedian TWA/QRS[IQR]Median ST/TWA[IQR]ACO (“STEMI”) (n = 33)1.08 [0.8-1.5]1.0 [0.8-1]no-ACO (n = 129)0.70* [0.43-0.75]0.67* [0.5-1]Non-STEMI (n = 24)0.51* [0.44-0.71]0.50* [0.5-1]no-MI (n = 105)0.66* [0.50-0.75]0.67* [0.5-1]*P < .05 compared to ACO, p = NS for non-STEMI vs no-MI. Open table in a new tab