Noninvasive 3D imaging of electrophysiological activity in the heart

Abstract

Abnormal cardiac electrical activity is the cause and manifestation of many forms of heart disease. The primary noninvasive diagnostic technique for detecting electrical dysfunction remains the electrocardiogram (ECG), which offers limited sensitivity and specificity. To obtain high-resolution data, an electrophysiological study (EPS) can be performed, in which a catheter with electrodes is introduced into the chambers of the heart. But this is invasive, time-consuming, and can be non-diagnostic. A more recent solution is electrocardiographic imaging (ECGI), 2 a noninvasive modality that provides high resolution three-dimensional images of cardiac electrical activity. ECGI uses multi-site potential measurements and the patient’s hearttorso geometry, derived from computer tomography (CT) images, to provide high-resolution maps. Surface potentials are recorded while the patient is fitted with a multi-electrode vest connected to a multi-channel mapping system. A chest CT scan is used to obtain heart and body surface geometry (Figure 1). Patented computer algorithms generate ECGI images in various useful formats. Over 30 human studies to date have applied ECGI. A technical report published in Nature Medicine introduced the methodology for clinical use. In another study, ECGI was validated through comparison with recordings of cardiac potentials obtained by placing electrodes in direct contact with the heart during openheart surgery. These results further substantiated ECGI’s ability to image cardiac electrical activity with high resolution and accuracy. Figure 2 shows close correspondence between electrograms (potential variation at each point on the heart) imaged by ECGI (black) and those directly measured during surgery (red). ECGI is also able to localize cardiac events, such as the origination of an abnormal heartbeat, with high resolution. Figure 3 Figure 1. Shown is the ECGI procedure. (a) The setup. (b) CT images showing heart-torso geometry. (c) Digitized heart-torso geometry. (d) Sample body-surface recordings. (e) Body-surface potential maps. (f) ECGI software. (g) Examples of ECGI images.