Signal quality and false myocardial ischemia alarms in ambulatory electrocardiograms

Electrocardiography (ECG) can be used to monitor patients for myocardial ischemia, which is a precursor to myocardial infarction. Ambulatory ECG is often contaminated with motion artifact. In this paper, we investigate the effect of motion artifact on myocardial ischemia alarms and on estimates of the ECG signal quality. The presence of motion artifact in an ambulatory ECG leads to false identification of myocardial ischemia. A signal quality index, based on the consistency of the shape of PQRST complexes, is able to automatically identify the degradation in signal quality associated with the false positive identification of myocardial ischemia. Since myocardial ischemia typically presents over longer periods of time than motion artifact, the signal quality index may be used to simply gate alarms generated during periods of poor signal quality. Consequently, the automatic detection of ambulatory ECG quality may lead to increased specificity of myocardial ischemia detection while maintaining the sensitivity of commercially available systems.