Danish study finds 51 percent greater odds, but absolute risk of a crash remains low
MONDAY, Aug. 29, 2016 (HealthDay News) -- People who have an implanted cardiac defibrillator (ICD) to control an irregular heartbeat appear to have more car accidents than similarly aged people without such devices, a new Danish study finds.
Overall, Danish drivers with ICDs were 51 percent more likely to be involved in a traffic accident over the two-and-a-half years of the study.
But the findings aren't necessarily a reason to tighten restrictions on these drivers, since the absolute risk of any one ICD-using driver being involved in an accident remained very low -- around 1 percent a year.
The issue is a tough one, said study lead author Dr. Jenny Bjerre, a physician at Herlev and Gentofte University Hospital in Copenhagen.
"On the one side, as physicians we need to take public road safety into consideration when we assess if these patients are medically fit to drive," she said. "But we also have to acknowledge that these restrictions have a huge impact on the patient's quality of life and personal freedom."
She presented the findings Sunday in Rome at the annual meeting of the European Society of Cardiology. Experts note that findings presented at medical meetings are typically considered preliminary until published in a peer-reviewed journal.
Dr. Mary Norine Walsh, president-elect of the American College of Cardiology, reviewed the new findings. She said that whether or not -- or when -- it's safe for people with ICDs to drive has been an issue for years.
According to Walsh, if a patient is given an ICD because of a history of passing out due to irregular heartbeat, "then the recommendation to the patient is that they not drive for [the first] 6 months" after implantation.
If the person has a condition such as heart failure, ICDs are often still recommended. Often this type of patient hasn't had a history of passing out due to irregular heartbeat, so there isn't a similar prohibition on driving, Walsh explained.
Bjerre said there's been little new data on the potential risks of driving for people with ICDs, since most studies date from the 1990s.
"In order to have contemporary and real-world data on the subject, we aimed to investigate motor vehicle accidents following ICD implantation in a nationwide cohort of ICD patients, and then compare them to an age- and sex-matched control population," she explained.
Her team tracked motor vehicle accident rates from early 2008 to mid-2012 for almost 4,900 Danish people with ICDs and almost 9,800 Danes of similar age but without such devices. Average age was 63.
Overall, 280 traffic accidents occurred during the study period.
"We found -- after adjustment for age, sex and alcohol abuse -- a 51 percent increased risk of motor vehicle accidents in the [ICD-patient] population," Bjerre said.
However, it's important to stress that the absolute risk of a traffic accident to any one person in the study was low -- a little over 1 percent in the first year after ICD implantation and 0.6 percent a year for people without the devices.
None of the accidents involving ICD users were fatal, Bjerre added.
Does any of this mean that current recommendations on driving after ICD implantation should be changed? Bjerre and Walsh agreed it's too soon to say.
Bjerre said there's no evidence the ICDs are "shocking" drivers and causing any accidents. Instead, it's probably the underlying illnesses that ICD users have that are at play, she said.
Walsh agreed. She also believes more insight could have emerged from the study if both groups had been similarly ill.
"They can't compare to a group with just the same age, the same sex patients -- they have to compare to patients who are equally sick," Walsh said. "Because with sickness comes frailty -- some of the reasons these people [with ICDs] had car accidents was because they were frail possibly, because they were ill."
And she agreed with Bjerre that barring an older person from driving is never an easy call.
"If the recommendation from this study becomes, 'Well, if you've had a defibrillator, you can't drive,' it's devastating," Walsh said.
She believes caution -- and better evidence -- is needed before doctors, insurance companies and policymakers make any changes to driving recommendations.
Bjerre agreed. She believes societies must always balance public safety against personal freedoms.
"We're never going to achieve a zero percent risk [of accidents], even in the general population," she said, "so I think it's up to society to decide which risk we do accept."
There's more on ICDs at the Heart Rhythm Society.