Portable Electrical Impedance Tomography Enables Heart Ejection Fraction Measurement for Health Screening in Nonspecialist Settings.

Heart failure (HF) is a circulatory disorder that affects 1-2% of the human population worldwide. This clinical syndrome is pathophysiologically associated with other cardiovascular diseases including ischemic heart disease, atrial fibrillation, and stroke. HF-associated deaths and complications (e.g. arrhythmias) may be preventable if the disease is detected early and intervened upon. While metabolic disorders such as high blood pressure, blood glucose, and cholesterol are regularly monitored in primary healthcare, organ health - including the heart - is often overlooked. A key measure of cardiac pump function that can provide supportive evidence of HF is the ejection fraction (EF). When the left ventricular EF, an indicator of systolic function, is reduced, the patient may develop signs and symptoms of HF. Approximately half of the HF patients requiring hospitalization have reduced EF. Echocardiography can detect structural and functional cardiac abnormalities non-invasively, but is relatively costly, resource-intensive, operator-dependent, and not scalable for community-level screening. To address these issues, we propose a novel method leveraging electrical impedance tomography (EIT), a portable, safe, and cost-effective modality. We introduce a technique to estimate EF using dynamic EIT of the heart with simultaneous electrocardiography (ECG)-gating, addressing the traditional issue of lung signals being much greater in magnitude than heart signals, even when subjects breathe normally during data acquisition. Key features of these dynamic EIT images at end-systole and end-diastole are extracted, enabling computation of EF. This method was validated against echocardiography data from 20 healthy human subjects, achieving a mean absolute error (MAE) of 1.48 and an R2 value of 0.76 (p < 0.001). By enabling EF measurement in a portable and scalable manner, our approach has the potential to bring cardiac screening to nonspecialist primary healthcare and community settings.Clinical Relevance-HF is a complication of many cardiac abnormalities. Left ventricular ejection fraction is an important measure of cardiac function to screen for HF. Portable EIT shows promise as a cost-effective tool for screening cardiac function, and potentially facilitating early diagnosis of cardiac abnormalities, including HF, at the primary healthcare level.