Stanford researchers launch iPhone app to study peripheral artery disease

Researchers hope people who have the condition will download the app and enroll in a study that will provide insights into patterns of the disease’s progression and may point toward new methods of treatment.

The VascTrac app is designed for people who have peripheral artery disease. It tracks a user's steps and activity during the day.
Norbert von der Groeben

Stanford University School of Medicine researchers have launched a free iPhone app designed to help them conduct a clinical study to discover better treatments for peripheral artery disease and as a convenient way for people with the disease to monitor their daily activity.

“We hope to gain insights into patterns of disease progression over time by collecting participants’ activity data from their iPhones,” said Oliver Aalami, MD, clinical associate professor of vascular surgery and lead investigator of the study. “We will be looking for any changes in activity patterns that may indicate disease advancement.”

Peripheral artery disease, which affects about 12 million people in the United States, is a circulatory problem caused by a buildup of plaque in the peripheral arteries, most commonly in the legs. Symptoms include cramping and pain while walking or climbing stairs. Treatment is directed at reducing leg pain and the risk of heart attack and stroke from clogged arteries.

‘It gets really painful’

“One of the key metrics we will look at is the greatest distance that people with PAD can walk without stopping,” Aalami said. “It gets really painful, and they have to stop and rest before continuing on.”

The VascTrac app will collect activity data using Apple’s ResearchKit, an open-source framework that allows iPhone users to easily join clinical research studies. Since its launch over a year ago, the software has been used by researchers to collect data on diseases ranging from diabetes to melanoma. Stanford researchers launched one of the first of these studies, MyHeart Counts, in the spring of 2015 to study heart disease. That study has enrolled more than 54,000 people so far.

Oliver Aalami (second from left) walks with members of his team that helped develop the app. They are Raheel Ata (far left), Neil Gandhi (second from right) and Sunaina Kongara (far right)
Norbert von der Groeben

Aalami said the goal for the PAD study is to enroll 2,000 to 5,000 participants, “much more than you can do with a traditional trial.”

One of the study’s aims is to see if people with PAD show sudden changes in activity level in the months after certain common vascular procedures, such as the use of stents and balloons to improve blood flow in the arteries. Knowing exactly when a sudden drop in activity occurs, rather than waiting for the traditional follow-up doctor’s visit, could potentially provide physicians and participants with a much better indication of when further intervention is needed. A sudden drop in activity level could be a sign of claudication — pain caused by too little blood flow to the extremities, commonly the legs, which indicates trouble.

“People with PAD may be able to walk five miles, but sudden pain may cause them to stop often,” Aalami said. These patients can rest, and the pain goes away and they move on, often not realizing they could be in trouble, he said.

Early detection would be ‘Holy Grail’

“Endovascular procedures such as balloons or stents in the iliac or femoral arteries are minimally invasive procedures that allow patients to go home the same day, and they work well, but are not that durable,” Aalami said. “The issue is that within a year or two, 60 percent of them fail because patients develop scar tissue. We’re not perfect at predicting who is going to have problems, and catching them early when these stents do go down would be the Holy Grail. It’s much easier to fix earlier.”

Traditionally, physicians tell patients to schedule follow-up visits at three-, six- and 12-month intervals after one of these procedures. But there’s a “black hole” in between visits when doctors don’t know what’s happening, Aalami said.

By using personalized tracking, participants could get a notification to come in for an ultrasound when physicians see signs of claudication. 

The app "could be a game changer,” said Neil Gandhi, a Stanford medical student and co-investigator of the study. “It could change the way physicians practice. By using personalized tracking, participants could get a notification to come in for an ultrasound when physicians see signs of claudication. This could ultimately improve care.”

The app is an example of Stanford Medicine’s focus on precision health, the goal of which is to anticipate and prevent disease in the healthy and precisely diagnose and treat disease in the ill.

Although the app is targeting people with peripheral artery disease, any iPhone user 18 years or older is qualified to participate in the trial.

“Because anyone can develop peripheral artery disease, and because we need healthy subjects as controls, we’re opening the study to anyone,” said Raheel Ata, a Stanford medical student and co-investigator of the study.

Participation will include a five- to 10-minute initial survey, followed by quarterly surveys on the iPhone and occasional tests to measure how far a participant is able to walk. To keep a daily tally of activity, users simply keep their iPhone with them during the day.

“We’ve tried to keep participation in this trial as simple as possible,” Aalami said. “The phone will passively measure total steps taken in a day, the number of stairs walked and the distance walked.” Participants can download the VascTrac app from the App Store.

Researchers emphasize that the app is not a medical diagnostic tool and isn’t designed to provide medical advice, professional diagnosis, opinion, treatment or health-care services.

All participants’ data will be stored using military-grade encryption, and participant names will be replaced by random codes, keeping identities and medical information confidential, the researchers said. With permission from a participant, his or her de-identified data may be shared with researchers at other institutions approved by Stanford.

The trial is being sponsored by the companies Abbott Vascular, Cook Medical, W. L. Gore & Associates and Microsoft.



Stanford Medicine integrates research, medical education and health care at its three institutions - Stanford University School of Medicine, Stanford Health Care (formerly Stanford Hospital & Clinics), and Lucile Packard Children's Hospital Stanford. For more information, please visit the Office of Communication & Public Affairs site at http://mednews.stanford.edu.

Leading in Precision Health

Stanford Medicine is leading the biomedical revolution in precision health, defining and developing the next generation of care that is proactive, predictive and precise. 

A Legacy of Innovation

Stanford Medicine's unrivaled atmosphere of breakthrough thinking and interdisciplinary collaboration has fueled a long history of achievements.