(Gerd Altmann, Pixabay)
6 September 2017. A medical engineering team designed a smartphone app that in a clinical study shows it can measure key factors in heart health as accurately as MRI scans. Researchers from California Institute of Technology in Pasadena, University of Southern California, and Huntington Medical Research Institute published results of their study in the July 2017 issue of Journal of Critical Care Medicine (paid subscription required).
The team led by Caltech’s Morteza Gharib, a professor of both aeronautical and biomedical engineering, is seeking ways of detecting heart disease that are more widely accessible. Heart disease, according to Centers for Disease Control and Prevention is the leading cause of death in the U.S., accounting for 1 in 4 deaths, or about 610,000 a year. In many people, heart or circulation problems have few noticeable symptoms, making it important to have regular screenings.
In most cases, however, those screenings need to occur at a doctor’s office or clinic and involve imaging technologies such as magnetic resonance imaging or echocardiograms that use ultrasound. Both of these methods require trained technicians, expensive equipment, and extended periods of time — 30 to 45 minutes — to complete. Providing a easier, less expensive, and portable technique to detect heart problems could help spot heart disease faster and earlier than current methods.
Gharib and lab colleagues are looking to smartphone technology to fill the gap. The team developed a smartphone app that detects and measures pressure variations in the walls in arteries in the neck that expand and contract similarly to heart. The researchers call these subtle pressure wave variations intrinsic factors, which in previous studies were shown to indicate changes in heart activity. The team also wrote an algorithm to calculate the relationship between intrinsic factors and a key measure of heart function called left ventricle ejection fraction that measures the amount of blood pumped with each beat.
The app uses the smartphone’s camera to detect changes in skin displacement above the carotid artery in the neck, with software to construct the pressure wave, and algorithm to calculate the intrinsic factors and estimate the equivalent left ventricle ejection fraction measurement. The stronger the pressure wave through the artery, the greater the amount of blood pumped from the heart through the artery.
In a proof-of-concept test of the app, the researchers recruited 72 volunteers ranging in age from 20 to 92 years that included individuals with heart failure. Participants used the app in an iPhone to estimate their left ventricle ejection fraction, and also undergo a cardiac MRI scan, a reliable and accurate technique, but also expensive. The app detection and measurements took 1 to 2 minutes, and required no special training or calibration.
The results show a high correlation — 0.74, with 1.0 being an exact correlation — between the app’s calculations of left ventricle ejection fraction and those made by MRI scans. Measurements made by the app varied within a 19.1 percent margin or error, say the authors, comparable to echocardiograms that have a 20 percent standard variation.
Gharib and colleagues are now looking into other indicators of heart health that the app can detect and measure. Caltech patented the underlying technology, with Gharib and three co-authors listed as the inventors. Those co-authors and inventors — Derek Rinderknecht, Niema Pahlevan, and Peyman Tavallali — recently founded the company Avicena LLC to further develop the app and take it to market.
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