Implantable cardioverter-defibrillators (ICDs) are literally lifesavers for the millions of patients who face a high risk for sudden death due to irregular heartbeats known as arrhythmias. But over the years, concerns have been raised as to how various environmental factors might make ICDs malfunction.
The new analysis tackled one such environmental phenomenon -- solar flares, or storms -- and found that they seemed to offer some measure of protection against the risk of arrhythmias and correlated with decreased ICD activity.
"To be honest, I have no idea why," said study author Dr. Elisa Ebrille, a cardiology research fellow in the division of cardiovascular disease with the Mayo Clinic, in Rochester, Minn.
"We don't know because until now there has been nothing in the literature that has suggested that solar flares are protective," she said. "So, we can't yet say if this is happening because the device is simply working more efficiently or because the patients are actually experiencing fewer arrhythmias."
Ebrille did note that solar flares are quite rare.
"They occur at a frequency that coincides with the sun cycle, and the sun cycle is something like 11 years long," she explained.
"But the thing is, cardio devices [ICDs] are essentially electronic devices," Ebrille noted. "And they can certainly be influenced by electrical activity in the environment, including abnormal electrical signals. And a major source of that comes from high-level solar radiation. Or flares," she continued.
"Some of the literature has indicated that during solar flares, arrhythmias become more frequent," she noted. "But by looking at geomagnetic activity and patient response, what we found, much to our surprise, is that there was actually a dramatic decrease in device activity prompted by heart irregularities."
Ebrille and her colleagues are to present their findings Friday at the Heart Rhythm Society annual meeting, in San Francisco. Research presented at meetings should be viewed as preliminary until published in a peer-reviewed medical journal.
Battery-driven and wired directly into the chambers of the heart, ICDs are surgically implanted to monitor and correct for heart trouble on a constant basis.
In recent years, remote monitoring has become a common feature of ICD maintenance, so doctors can track activity without an actual office visit with the patient.
"And what this means," Ebrille said, "is that now, for the first time, we have a large amount of patient data to explore in a search for a relationship between solar flares and device function."
The team sifted through information gathered between 2009 and 2012 on ICD function among a daily grouping of an average 60,000 patients.
ICD function was then stacked up against daily geomagnetic activity as reported by the U.S. Space Weather Prediction Center, which ranked solar activity as being at either "quiet," "unsettled," "active" or "storm" levels.
The result: during the study, "storms" occurred about 2 percent of the time, and when they occurred the frequency with which the patients experienced ICD corrective measures dropped.
In fact, the team concluded that there was a "significant" inverse relationship between high solar flare levels and ICD activity, so that the greater the flaring the less often patients seemed to need their ICDs to kick into gear.
Dr. Michael Gold, chief of cardiology at the Medical University of South Carolina in Charleston, described the findings as both "novel and intriguing."
"We know that patients' bodies and hearts are affected by a lot of environmental factors -- factors that we don't comprehend very well -- stresses in people's lives, activity levels, diet," he said. "So the idea that magnetic fields could also have an impact is certainly not preposterous," Gold noted.
"But until recently it's not been so easy to look at," Gold explained. "The difference today is that most our defibrillation patients are now on a monitoring system, where we can keep track of them and collect an enormous databank of information to analyze. And by doing exactly that, these researchers have been able to suggest that the impact of higher magnetic radiation is actually positive, which should be somewhat reassuring to people," he added.
"However, this is not a randomized study," Gold cautioned. "So this needs to be put into context. And there will need to be further confirmation of this finding."
While the study showed an association between solar flares and ICD function, it could not prove a cause-and-effect relationship.
Visit the U.S. National Heart, Lung, and Blood Institute for more on ICDs.