March 30, 2014

WASHINGTON, DC — Think about what it's like not to be able to drive, Dr Joshua M Cooper (Temple University, Philadelphia, PA) asked attendees here at the American College of Cardiology 2014 Scientific Sessions .

"We take it for granted when we can drive, but the moment it's taken away, people suffer—economically because they can no longer work, socially, [and] they can't drive to get food," Cooper said, launching his argument in the staged debate. The notion at stake, which Cooper defended: a patient with prior ventricular tachycardia (VT) who has not had a shock in three months is safe to drive now.

Equally strident in challenging the idea, Dr Steven M Markowitz (New York-Presbyterian/Weill Cornell Medical College, NY) proposed the scenario of a patient with an implantable cardioverter defibrillator (ICD) driving a car at 60 mph who receives a shock.

"If the patient is disoriented and inattentive for one second, that car will move about 88 feet," he said. "That distance is about four car lengths, certainly enough to cause an accident." And the reality, he added, is that the lapse in focus would go on longer, at least two or three seconds. "And I would argue that it could occur with any shock, even an inappropriate shock."

Loss of Consciousness While Driving Rarely Fatal

"In order for somebody to have an accident, they need to have the arrhythmia while they're driving. They have to be suddenly incapacitated; they have to lose control of the vehicle, crash the vehicle, and sustain injury or death. And this almost never happens," according to Cooper.

He displayed results from a half-dozen published studies that recorded what happens after sudden incapacitation while driving due to various medical conditions. "What was striking about these six studies is that even though over 300 patients collectively lost the ability to control their vehicle all of a sudden, fewer than half actually had an accident. And from those accidents, there were only six injuries and one death."

He added, "Of course you want to prevent any fatality you possibly can; but the question is, should you rob everybody of the right to drive to save very few people?"

Showing a timeline graph for recurrent arrhythmias following a shock for VT, Cooper pointed out "the slope is steepest at the beginning. The highest risk is in the first month or two." Thereafter, the monthly differences in risk of recurrent VT are much smaller.

And there's evidence that the driving period itself isn't when shocks are likely to happen. In one study he described, the absolute risk of a shock within an hour of driving in 23 patients was one in 25 116 person-years. Of 44 shocks within one hour of driving, 37 occurred within 60 minutes after driving.

So You Yank Their License–What Then?

In the Antiarrhythmics Versus Implantable Defibrillators (AVID) study, Cooper noted, participants completed surveys about driving issues; the response rate was a whopping 83%, suggesting patients were eager to address the subject. Of respondents, 64% said doctors have raised the question of driving with them. Of those who had been told not to drive, 59% reported the restriction was a severe hardship and 35% said there was "no other driver in the house. So suddenly, you're completely taking away someone's autonomy."

Then there is the restriction's psychological impact, he said. In one analysis of bans on driving for various medical reasons, after patients got instructions not to drive, there was a 27% jump in emergency room visits for depression, 29% of participants visited their doctor less often, and 10% stopped seeing their doctor altogether.

"There's an erosion of trust in the doctor-patient relationship, and arguably healthcare, if you tell the patient they can't drive. So make sure you get it right if you're going to revoke that right."

And people should look elsewhere if they really want to decrease the car accident rate. Cooper showed a line graph of fatal accidents per 100 million miles driven by age, which had two peaks, one at age 19 and the other at about age 85. "It's the young patients and old patients who crash and kill people, including themselves, so if you really want to make a difference, then don't have really young and really old people drive. But don't take away the liberty of patients who have defibrillators who are in the middle of this J curve with low accident rates."

About Those Studies You Cited . . .

The studies cited show very low risk of shocks, accidents, and fatalities among ICD patients when driving, Markowitz agreed. But nearly all were observational and retrospective. Many were based on surveys and hampered by significant recall bias, as well as "strong disincentive [for ICD patients] to admit that they were driving."

And much of their data come from years ago and aren't necessarily relevant to modern driving habits, he proposed. "More patients are driving in an urban environment, on more congested roadways, with drivers distracted by cell phones, [unaware] that a car may be swerving into the lane in front of them. So we need more up-to-date data."

For that, Markowitz referred to sections of the Ontario Road Safety Annual Report 2010 on accidents due to medical disorders and noted a fatal- or major-injury rate of 4%. "This is double what has been assumed in consensus statements [on ICDs and driving] and all those models [predicting harm from driving after VT]."

If the contemporary rate of 4% is plugged into those models, "it turns out that we exceed our [accepted] risk of harm not for three months, but for 12 months after a patient receives an ICD shock."

Markowitz proposed that driving instructions in ICD patients be individualized, and Cooper agreed. "Perhaps we should resist the urge to fall back on arbitrary recommendations, a one-size-fits-all guideline of three months," Markowitz said. "Maybe we should think about how often a patient drives and how high a risk of VT or [ventricular fibrillation] VF that patient has." And, he said, things like whether the patient is likely to have syncope in the first place and locations where the patient is likely to drive should also be considered.

Cooper disclosed receiving consulting fees or honoraria from Medtronic, Biotronik, Boston Scientific, St Jude Medical, and Spectranetics. Markowitz had no disclosures.


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