Driving and Vasovagal Syncope? Serious Accidents, Harm Rare

Marlene Busko

January 28, 2016

CALGARY, ALBERTA — Researchers estimate that the incidence of driving and having a serious accident causing bodily injury or death is much lower in patients with frequent vasovagal syncope than in the general population (<0.0035% per person year vs 0.067% per driver-year)[1]. The study was published online January 20, 2016 in JACC: Clinical Electrophysiology.

In this largest analysis of this risk to date, Dr Vern Hsen Tan (University of Calgary, Alberta, and Changi General Hospital, Singapore) and colleagues analyzed data from 418 adults from the combined Prevention of Syncope (POST) 1 and POST 2 trials.

Based on case records, they found that during a mean follow-up of 0.77 years, two patients fainted while driving. One had a prodromal syndrome and pulled off to the side of the road, and the other had minor bodily injuries.

The study provides some initial information that may help guide policy makers, and it will also help inform physicians who are treating patients with vasovagal syncope, senior author Dr Robert Sheldon (University of Calgary) told heartwire from Medscape.

There are two takeaway messages for clinicians. First, "this at least gives some information on how to talk with a specific patient [with vasovagal syncope] about what their risk [of an accident while driving] is," he said. The study showed that "the likelihood of a motor-vehicle accident in patients with moderately frequent vasovagal syncope is very low and well within societal tolerance based on general motor-vehicle accident rates."

Second, despite this low risk, "You've got to know the law, [and clinicians] have to obey the law," which is very different in various US states and Canadian provinces, he said. For example, in Alberta, clinicians need to discuss driving limitations with patients with vasovagal syncope, whereas in Ontario, clinicians also have to inform authorities.

Is It Safe to Drive With This Condition?

Vasovagal syncope is common and affects a third of men and more than 40% of women, according to Sheldon. Yet little is known about fatalities and injuries from fainting while driving. There is a lack of evidence-based studies to shape clear guidelines for restricting driving in patients with vasovagal syncope, and largely because of this, the provinces and states have different laws.

Sheldon noted that recommendations in the Canadian Cardiovascular Society (CCS) Fitness to Drive Guideline[2] for driving restrictions with cardiac conditions are tethered to a benchmark that comes from the risk that a commercial truck driver would incur following an MI. The recommendations aim to keep the risk of serious harm or death due to sudden cardiac incapacitation to less than one per 20,000 per driver-year (0.005%).

To estimate the incidence and outcomes of vasovagal syncope while driving, Tan and colleagues analyzed data from POST 1 and 2 and then compared their findings with current UK, US, and Canadian data about motor-vehicle accidents.

POST 1 randomized 208 individuals with vasovagal syncope who were seen from 1998 to 2003 in study centers mainly in Canada, but also Columbia, Germany, the US, and Australia to receive the beta-blocker metoprolol or placebo.

POST 2 randomized 210 similar individuals seen from 2006 to 2011 in study centers mainly in Canada, but also Columbia, the US, and Poland, to receive fludrocortisone or placebo. Neither therapy significantly reduced the risk of syncope during a follow-up of about a year.

In the combined two trials, the participants had a mean age of 38+17 years, and they had their first fainting episode at age 22. They had fainted a median of 10 times in their lives including a median of three times in the year prior to enrollment.

During a mean follow-up of 0.77 years, 174 study participants had 615 fainting episodes, and two participants (one in POST 1 and one in POST 2) fainted while driving. Thus the likelihood of fainting while driving was 0.62% per person-year and the estimated risk of a serious injury or death caused by fainting while driving was <0.0035% per person-year.

Based on data for motor-vehicle accidents and casualties, the researchers estimate that in the general population in Canada, the US, and the UK, from 2009 to 2012, the risk of either serious harm or death from driving was 0.067% per driver-year, and the risk of death was 0.009%.

Several Study Limitations, More Research Needed

Tan and colleagues acknowledge several study limitations. POST 1 and POST 2 were not designed to evaluate syncope and driving, and on average, patients were followed for under a year. Moreover, very few patients were older than 70, so the results cannot be generalized to elderly drivers.

Importantly, they had no information about the advice about driving that clinicians gave these patients or whether the clinicians followed provincial or state guidelines for driving restrictions. However, in Alberta, where 170 of 418 patients lived, patients who faint are very rarely prohibited from driving for more than a week, according to the researchers.

In addition, they had no information about patient compliance with advice they received about driving.

On the other hand, this was the largest reported patient cohort, and "the follow-up duration captures a reasonable horizon of clinical decision making," according to Tan and colleagues.

"Much larger and prospectively designed studies are required to provide more precise estimates of risk for policy makers," they urge.

POST 1 and 2 were supported by grants from the Canadian Institutes for Health Research. The authors have no relevant financial relationships.

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