Heart patients with implantable cardioverter defibrillators often undergo a series of health care procedures when they receive shocks from the devices, regardless of whether the shocks are necessary, a Stanford researcher says.
A team led by a Stanford University School of Medicine researcher has discovered that shocks from implantable cardioverter defibrillators often trigger a cascade of health tests and interventions, even when the shocks they deliver are not needed.

A study describing the team’s findings was published online Feb. 14 in the journal Circulation: Cardiovascular Quality and Outcomes. The lead author is Mintu Turakhia, MD, assistant professor of cardiovascular medicine at Stanford.

The study analyzed data from patients who were implanted with ICDs between 2008 and 2010. The health care costs of dealing with shocks from ICDs ranged between about $1,300 and $20,000 per patient for outpatient and inpatient care, regardless of whether the shocks were necessary, the team reports.

Unnecessary shocks can occur if there is a problem with the defibrillator system itself – for example, if a wire breaks, resulting in electrical noise that the system mistakes for an abnormal heart rhythm, or if the implant responds to abnormal heart rhythms that it’s not meant to treat.

“Sometimes the defibrillator gets tricked, and it misinterprets what the rhythm is,” said Matthew Reynolds, MD, a study co–author and cardiac electrophysiologist at the Lahey Hospital and Medical Center in Massachusetts.

“You’re putting these in to do their job to save patients’ lives,” said Turakhia, who is also the senior director of research at the Stanford Center for Digital Health and a practicing cardiac electrophysiologist. “But we live in a bit of duality with implantable defibrillators.”

Interested in trying to understand that contradiction, Turakhia and his colleagues began by tackling the challenge of linking implant data with electronic health records for 10,266 U.S. patients. The team took a freestanding data set of remote monitoring of ICDs and pacemakers and linked it to the patients’ clinical information, making it one of the first and largest such studies of its kind, Turakhia said.

“That’s one of the big innovations here, especially as we start thinking about big data and precision health,” Turakhia said. “Linking data across multiple domains – indirectly and without patient identifiers – is the wave of the future to understand disease, care and outcomes.”

In the linked data, the team picked 963 patients who had received an ICD shock more than once. They found that over one–third of administered shocks were inappropriate and nearly half the patients who experienced a shock received some form of health care related to it.

But researchers were surprised to find that patients who got a shock were hospitalized one out of seven times. Patients often had to go through procedures like stress tests, cardiac catheterization and echocardiography. “It didn’t really matter why the shock occurred,” Turakhia said. “The very fact that any shock happened at all triggered all that stuff happening to the patient.”

These findings indicate that reprogramming the devices so they are smarter and more selective about when to send shocks may help further reduce health care expenditures. At the same time, patients do better if doctors program the ICDs to shock less, or more conservatively, previous studies suggest. “Fortunately, the industry has made many advancements in this area,” Turakhia said. “Even older–generation devices can be programmed to be smarter. The quality of care is no longer just an issue of whether an ICD was implanted in appropriate patients but also whether it was programmed in the best way possible.”