New Electrocardiographic Criteria to Differentiate Acute Pericarditis and Myocardial Infarction: Rossello X, Wiegerinck RF, Alguiersuari J, et al. Am J Med 2014;127:233–9.

Abstract

Accurately diagnosing ST-segment elevation myocardial infarctions (STEMIs) in the emergency department can prove to be a challenging task, and misdiagnosis can lead to unnecessary coronary angiography. This article from four tertiary hospitals in Spain sought to improve the distinction between pericarditis and STEMI by examining the duration of the QRS complex and QT interval. The authors hypothesized that the QRS interval would be prolonged in acute MI due to slowed propagation of the local activation front by transmural ischemia; the QT interval was expected to be shortened in the acute period. They performed a multi-centric case-control study examining 150 patients with acute chest pain associated with ST elevation: 71 who presented with STEMIs and 79 who had acute pericarditis. Admission electrocardiograms (ECGs) were manually analyzed for deviation of the PR segment from baseline, ST-segment deviation from the J-point, QRS duration, and QT interval. Each ECG was analyzed using one of three models: Model A included the duration of the QRS complex and QT interval; Model B utilized the classic ECG criteria of PR deviation and J-point level in aVR, as well as the number of leads with ST-segment elevation, ST-segment depression, and PR depression; and Model C tested all of the above variables. Receiver operating characteristic curves (ROCs) were constructed for each model, and the ROCs were compared using the DeLong method. Overall, patients with acute pericarditis were younger with fewer cardiac risk factors. Additionally, these patients showed greater upright PR deviation and deeper J-point in aVR, as well as a higher number of ECG leads with ST elevation and PR depression and a lower number of leads with reciprocal ST depression compared to STEMI ECGs. In patients with pericarditis, the QRS and QT intervals were the same in leads with and without ST elevation, whereas patients diagnosed with STEMIs showed a longer duration of the QRS complex and shorter QT interval length in leads with ST elevation compared to isoelectric leads. Comparison of the aforementioned models showed improvement in the ROC when QRS and QT interval duration were included in the analysis, with the ROC for model A being 0.807, model B 0.863, and model C 0.914. This study demonstrates that factoring the QRS duration and QT interval in your analysis of an ECG can help the clinician identify pericarditis and acute STEMI. The authors note that the study was limited by a lack of randomization, and that the ECG findings significantly influenced the ultimate diagnosis for patients at discharge.