Syncope on the Highway

abstract & commentary

Synopsis: Syncope during driving is not uncommon among patients referred for HUTT and aggressive medical attention is required for these patients.

Source: Haugui L, et al. Am J Cardiol 2000;85: 184-186.

Syncope is a common complaint and vasovagal episodes are the most frequent etiology. However, little is known about vasovagal syncope during driving. Thus, Haugui and associates reviewed the head-up tilt table test (HUTT) records of 245 consecutive patients over six years at the University of Nebraska Medical Center and found 23 patients (9%) who had one or more episodes during driving. HUTT was diagnostic of vasovagal syncope in 19 of the 23 and negative in the other four. With the exception of treated hypertension in three patients, no other cardiovascular disease was found in these patients. All but three patients had multiple episodes of syncope (2-10), but most only had one driving episode. Most of the patients had syncopal episodes before the driving episode and most had warning symptoms before the attack. All the syncope driving episodes caused property damage, despite the fact that in one-third of the cases there was a passenger in the car who witnessed the episode. Almost half of the drivers sustained personal injury and one incident caused the death of another driver. After HUTT, 19 patients received pharmacologic therapy and 14 of these patients underwent repeat HUTT. HUTT showed persistent vasovagal syncope in half, and most of them had their medications adjusted. During an average follow-up of 51 months, recurrent syncope occurred in four patients with initially positive HUTT, one episode of which was during driving in a patient on therapy with a negative repeat HUTT. Recurrent syncope did not occur in patients with an initially negative HUTT and another cause of syncope was never documented in those with recurrent episodes. Haugui et al conclude that syncope during driving is not uncommon among patients referred for HUTT, and aggressive medical attention is required for these patients.

Comment by Michael H. Crawford, MD

Syncope while driving is usually attributed to Stokes-Adams episodes (severe brady- or tachyarrhythmias). Thus, this report is of interest because it substantiates that vasovagal syncope should be considered in the etiology of syncope during driving. The relative proportion of vasovagal vs. other causes of syncope during driving is not given in this study, but presumably other causes would be more frequent. In this study HUTT was only done after other causes were excluded, which included electrophysiologic testing in some patients. No other heart disease was discovered in these patients. Only 13% had hypertension under medical control and there was no evidence that the syncope was orthostatic due to medication excess. HUTT was positive in 83%, but there has been concern about false-positive HUTTs, especially in young patients. Thus, it is conceivable that some of these patients did not have vasovagal syncope, but clearly many did since there was evidence of recurrent events and positive repeat HUTT. False-negative tests are also possible and four patients had negative tests. Only one of these patients was empirically treated with beta-blockers, yet none had a recurrence. These four patients probably had some other nonrecurrent mechanism for their syncope.

This study also demonstrates the difficulty these patients present for treatment. Recurrences occurred despite therapy, one during driving again. Repeat HUTT was positive in half of those undergoing treatment, but we do not know how predictive this test is of recurrence. However, the low rate of recurrence was encouraging, demonstrating that treatment was worth the effort. The risk of recurrence was substantial since personal and property damage with the driving episodes was common. Given the uncertainties of therapeutic success, driving should be restricted in such patients for at least three months. Some states have specific laws and some do not regarding resumption of driving. Also, in those that do, the laws vary from state to state. Physicians treating patients with syncope should become familiar with the laws in their state.

Syncope while driving:

a. can be vasovagal.

b. is almost always ventricular tachycardia.

c. usually results in the death of the driver.

d. rarely causes property damage.