"Water is an attractive source for electrical activity," Shmorhun explained. "We don't think there would be an issue at all in, say, the ocean or bay. But in a pool, where you have wires coming into the water from the outside, from the house, from an aging utility system, or an improperly grounded system, there is a potential for this kind of problem. Or if a pool is not properly bonded -- meaning the pool circumference is not intact -- there could be a problem," he noted.
"I'm not sure anybody can really predict up front what pools are an issue, and there's no practical means by which to easily test pools for this," Shmorhun added. "At the same time, we don't know the overall incidence, although three cases in the Austin area in one year seems like a lot to me. But at minimum, [defibrillator] patients need to be counseled about the risk."
For his part, Heart Rhythm Society vice president Day said the finding should not deter patients from swimming.
"We want our cardiac patients to be physically active. We don't want to restrain them and we don't want to create alarm," Day said.
"But in each of these cases we had these underwater pool lights that had an alternating current pool leak that could trigger a shock," noted Day, who is also director of Heart Rhythm Services at Intermountain Medical Center in Murray, Utah. "So, I think we certainly need pool safety. And clinically this is just one more thing that should be considered as a potential source of a problem for any patient with an implantable defibrillator."
Find out more about heart arrhythmias at the U.S. National Heart, Lung, and Blood Institute.
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