A group of researchers from the University of Southern California and the California Institute of Technology have developed a medical app designed to measure left ventricular ejection fraction.
Hopefully you read that first line with a healthy skepticism, as we did when we first saw the paper describing their work. Currently, ejection fraction is most commonly measured using an echocardiogram, with the modern gold standard generally considered to be cardiac MRI. In this study, a group of researchers explored whether there was a simpler, non-invasive way to get some assessment of LVEF.
Pahlevan et al explored the idea of using a modified iPhone camera to capture skin displacement images on the patient’s neck above the right carotid artery to calculate LVEF. Two hidden oscillations, called intrinsic frequencies, from the waveforms derived from these images are identified to represent the coupled and decoupled aortic system before and after the aortic valve is closed. These intrinsic frequencies are then used to calculate the ejection fraction of the patient.
Seventy-two patients were included in this study, ranging from 20 to 92 years old. The results from this method correlated well with MRI results (r=0.74; P<0.0001), with the additional benefits of being non-invasive and operator/reader independent, as everything is calculated by the intrinsic frequencies algorithm embedded in the app.
The iPhone was mounted on a fixed holder for these tests, providing convenience and stability for image capture and supports the notion of using this setup to gather continuous LVEF measurements.
This study was generally a proof of concept that smartphone technology can be used to provide accurate LVEF measurements. As a point-of-care tool that could have interesting applications, in both the outpatient clinic as well as emergency department, as a screening tool, much in the way point-of-care ultrasound is used. The idea of continuous LVEF measurements seems interesting though it’s not entirely clear how that would be clinically useful. That said, this medical app is just a proof of concept and is clearly a work in progress.