Interpretation of the electrocardiogram: clinical correlation suggested.

Vijayaraghavan et al. have investigated the interpretation of the initial 12-lead electrocardiogram (ECG) in acute coronary syndrome (ACS) patients, focusing on the patient with potential ST segment elevation myocardial infarction (STEMI). The authors emphasize the importance of accurate ECG interpretation by the acute care physician (i.e. emergency physician, internist, and cardiologist). The authors compared the initial interpretation of the initial admission ECG by the treating physician with the interpretation of the same tracing by a physician at the core electrocardiographic laboratory. The ECG interpreters at the site were acute care physicians (emergency physician, internist, and cardiologist); at the core lab, the ECG was interpreted by non-cardiologist physicians using specific definitions of abnormality—in this case, ST segment elevation was defined as .0.1 mV in two contiguous leads. The subgroup of patients used in the study were taken from the Canadian ACS Registry and comprised 1310 patients, of which 1202 had complete data and were used for analysis. The definition of STEMI included ST segment elevation and a positive biomarker. What is unclear is whether a positive biomarker was a single spot test or the more appropriate ‘typical rise and fall’ pattern. Overall concordance between core-lab and site interpretation of the admission ECG was 62%. The calculated kappa value was 0.49, indicating modest agreement. When compared with the agreement group of the study, patients in the discordant subgroup were older with higher rates of diabetes mellitus, angina, myocardial infarction, congestive heart failure, coronary artery bypass grafting, and percutaneous coronary intervention. Patients with core-lab-defined ST segment elevation that was not noted by the treating site, who also had a positive biomarker, were significantly less likely to receive aspirin, heparin, and reperfusion therapy when compared with patients with core lab-site ECG interpretation agreement. After adjusting for other validated prognostic factors, site-unrecognized ST elevation was independently associated with higher mortality, most probably because of the increased rate of co-morbidities in this subgroup. It is interesting to note that a minority of this ‘site-unrecognized STEMI’ group did, in fact, receive reperfusion therapy somewhat later in the course of care (53 patients or 14% of this subgroup). Furthermore, another small portion of these patients had significant contraindication to fibrinolysis and, therefore, did not receive reperfusion therapy (92 patients or 24% of this subgroup). The authors concluded that significant rates of disagreement are found in the recorded interpretation of patients presenting with ACS—in particular, rates of ST segment elevation determination. Further, they note that the unrecognized STEMI is associated with underutilization of evidence-based therapies as well as worsened 1-year outcome (i.e. increased mortality). The study of Vijayaraghavan et al. is quite interesting for a number of reasons; it focuses on the all-important ability of the physician to interpret the ECG in the acute care setting—we must not lose sight of this message. Yet, there are several issues of concern that must be discussed, including the definition of acute myocardial infarction, the presence of non-STEMI ST segment elevation syndromes, outcome issues in the interpretation disagreement group, and reality of acute care clinical practice. Much of the disagreement between interpretations of identical ECGs may be due to differences in the clinical context in which the ECG is used. One interpretation takes place at the point of care, whereas the other takes place in isolation without the benefit of having a patient to assess. Point-of-care interpretation probably benefits from the patient’s clinical status (are they pain free?) and availability of previous tracings. It should be noted that the disagreement between ECG interpretations worked both ways; there were 335 cases where the site noted ST-elevation that was ‘missed’ by the core-lab interpretation, compared with