New Implantable Device at Saint Louis University Hospital Diagnoses Irregular Heart Rhythms 
Monday, 18 February 2013 

ST. LOUIS - Cardiologists at Saint Louis University Hospital have a new implantable tool to monitor patients’ irregular heart rhythms to prevent repeat strokes or fainting issues.

The Reveal DX device –about the size of a standard USB drive – is implanted under the skin near a patient’s chest and records an electrocardiogram (ECG) for up to three years. Because it can monitor continuously for up to three years, the likelihood of capturing heart rhythm information during an infrequent episode is probable.

“This allows us to confirm or rule out an abnormal heart rhythm more accurately than other tests,” says Scott Ferreira, MD, cardiac electrophysiologist at the Center for Comprehensive Cardiovascular Care at Saint Louis University Hospital and a SLUCare physician. “Patients used to leave with an external monitor, but they have to be wearing it during an actual episode.” In addition, Dr. Ferreira says many patients feel external monitors are difficult to wear and struggle with how to put them on. And with the external devices only recording 30 days of heart rhythm, it limits the amount of data a physician can study. 

“The implantable monitor makes it simple for the patient and doctor, and can be used long term,” he says.

Dr. Ferreira says there are two types of patients who the technology is appropriate for.

One, patients who struggle with fainting issues like syncope or palpitations. Using the device, cardiologists can review the patient’s heart rhythm during the episode, allowing physicians to better determine cause of fainting and if there is an abnormality. Historically, these episodes are difficult to diagnose as they are often infrequent and unpredictable for detection with conventional monitoring techniques.

The other patient group is growing – those who suffer a cryptogenic stroke, one which cannot be attributed to any specific cause.

For those patients, often underlying atrial fibrillation – or AFIB – is the cause. The irregular heart rhythm is a major stroke risk factor as AFIB allows blood to pool in the heart. When blood pools, it can form clots which can then be carried to the brain, causing a stroke. It is estimated that one-third of patients with AFIB are undiagnosed.

“This gives us the tool to pick up atrial fibrillation we didn’t have in the past,” says Dr. Ferreira. “We want to catch this before there’s another stroke that could be debilitating.”

To store the heart rhythm, a patient places a hand-held, pager-sized activator over the device after experiencing an episode, and presses a button. Even if a patient is not able to press the button, the device also has passive settings, automatically recording abnormal rhythms without the patient having to do anything. Later, a physician analyzes the stored information and determines whether the episode was caused by an abnormal heart rhythm.

From there Dr. Ferreira and his colleagues can determine treatment options, including medications, pacemakers or implantable cardioverter defibrillators (ICD) or cardiac ablation.

For more information about AFIB or the Center for Comprehensive Cardiovascular Care at Saint Louis University Hospital, visit



About Saint Louis University Hospital
Saint Louis University Hospital is a 356-licensed bed quaternary/tertiary referral center located in the heart of the city of St. Louis. Approximately 75 percent of patients are drawn from a 150-mile radius. Through affiliation as the teaching hospital for Saint Louis University, the hospital provides patients and their families with an environment of medical innovation. Working in this endeavor are the hospital’s medical staff partners, SLUCare, the physicians of Saint Louis University. The hospital admits more than 17,000 patients annually, performs more than 200 organ transplants a year and is a Level I Trauma Center that treats more than 2,000 major trauma cases a year. For more information, please visit

Jason Merrill