The QRS-T angle provides added diagnostic accuracy on top of standard electrocardiogram (ECG) criteria for patients with suspected non-ST-elevation myocardial infarction (NSTEMI), according to a study published in the International Journal of Cardiology. Furthermore, the QRS-T angle is an independent predictor for all-cause mortality in this patient population.
Authors of this large observational multicenter cohort study sought to evaluate the efficacy of the QRS-T angle for diagnosing patients with NSTEMI and for predicting an increased risk of mortality during a 2-year follow-up period.
The study cohort included 2705 consecutive patients aged 18 years or older who experienced symptoms suggestive of NSTEMI. The QRS-T angle was calculated from a standard 10-second resting 12-lead ECG recorded during the patient’s initial assessment in the emergency department.
After hospital discharge, patients were followed for 2 years for all-cause mortality outcomes, reporting at 3, 12, and 24 months. Diagnostic value and accuracy was estimated for both the independent and combined performances of QRS-T angle and ECG score. Researchers determined the usefulness of these diagnostic models and of the prognostic models using decision curve analysis.
Of the 2705 patients, 412 (15%) were diagnosed with NSTEMI. In the overall cohort, the median QRS-T angle was 27°; patients with greater QRS-T angles were associated with baseline characteristics that included older age, more cardiovascular risk factors, and a history of coronary artery disease, acute myocardial infarction, and myocardial revascularization.
When comparing patients with NSTEMI to those with other causes of chest pain, researchers found that the QRS-T angles were significantly greater in the former (P <.001). The diagnostic accuracy of the QRS-T angle for non-ST-elevation myocardial infarction as quantified by the area under the curve was 0.67 (95% CI, 0.64-0.70; P <.001).
The combined use of standard ECG criteria and the QRS-T angle significantly increased the sensitivity of the ECG for non-ST-elevation myocardial infarction, from 45% to 78%, and increased specificity from 86% to 91% (P <.001 for both). According to QRS-T angle tertiles, the cumulative 2-year survival rates were 98%, 97%, and 87% (P <.001). In univariate analysis, the QRS-T angle predicted mortality with a hazard ratio of 1.32 (95% CI, 1.26-1.4; P <.001) per 10° increase in angle; in multivariate analysis, the QRS-T angle predicted mortality independent of other clinical factors, including age and ECG confounders.
A limitation of the study was only including patients admitted into the emergency department for symptoms suggestive of acute myocardial infarction; the findings may not be generalized to other populations. Furthermore, the authors did not record serial ECGs, which could have increased the diagnostic value of the ECG by detecting dynamic changes, nor did they assess the value of QRS-T angle in patients at rest.
The authors found that the QRS-T angle derived from ECG data was significantly higher in patients with suspected NSTEMI and in older patients with more cardiovascular risk. The use of the QRS-T angle with standard ECG criteria improved diagnostic accuracy for NSTEMI. Furthermore, the QRS-T angle was a powerful predictor of all-cause death during follow-up.
Multiple authors declare associations with the pharmaceutical industry. Please see original reference for a full list of authors’ disclosures.
Strebel I, Twerenbold R, Weussler D, et al. Incremental diagnostic and prognostic value of the QRS-T angle, a 12-lead ECG marker quantifying heterogeneity of depolarization and repolarization, in patients with suspected non ST-elevation myocardial infarction [published online September 19, 2018]. Int J Cardiol. doi:10.1016/j.ijcard.2018.09.040