Modified Lewis ECG Lead System for Ambulatory Monitoring of Atrial Arrhythmias

Abstract

The analysis of atrial activity (AA) during atrial arrhythmias can be problematic when a reduced lead system is used due to low amplitude and noise. Although leads for AA enhancement were proposed many years ago by Sir Thomas Lewis, two electrodes need to be placed directly on the chest, and therefore arm movement artefacts are likely to occur. In this study, we propose a modified Lewis lead system better suited for ambulatory applications where the electrodes are placed in areas with less muscle. The proposed modification was compared to the Lewis leads as well as to the ES lead of the EASI system. Forty-one healthy volunteers and 8 patients with atrial fibrillation participated in the study. The results show that the proposed lead exhibits the best atrial-to-electromyographic activity ratio, with twice as large AA amplitude as the original leads. Furthermore, the atrial-to-ventricular activity ratio is 50% better than that of the ES lead. The results suggest that the proposed modification of the Lewis lead system has a potential to improve ambulatory monitoring of atrial arrhythmias. 1. Introduction While it is well-known that atrial fibrillation (AF) is a progressive disease, with brief episodes evolving into longer and eventually persistent, a recent debate has arisen whether brief episodes of AF are related to cryptogenic ischemic stroke [1], [2]. The hypothesis that brief AF episodes (< 30 s) can contribute to thrombus formation has yet to be proven, and thus automatic detection of very short episodes could accelerate more accurate diagnosis. The problem of false alarms due to electromyographic (EMG) noise, motion artefacts, and ectopic beats of commercial equipment for AF detection [3] forces cardiologists to review softwaredefined arrhythmia episodes manually, especially if AF events are brief [1], [2]. Since manual revision is exceedingly time-consuming and sometimes unreliable [4], increased accuracy [...].