A 55-year-old male was driving his car on the highway during daytime hours when he abruptly passed out behind the wheel. The car was totaled, but miraculously, he and his wife were unharmed. The patient is a reasonably healthy, middle-aged man. He doesn’t take any medications, and he has never experienced a syncopal event before. The patient would like to drive again soon. What clinical work-up should be done, and when, if ever, can he drive again?
Syncope is defined as “a temporary interruption of global cerebral perfusion that causes a sudden onset of transient loss of consciousness and postural tone with spontaneous recovery.”1 Syncope is fairly common — it accounts for up to 6% of hospital medical admissions and can recur in up to 22% of such patients.2
There is a long list of conditions which can cause syncope, ranging from the benign and bizarre to the truly malignant.1,2 The most common entity is vasovagal or neurocardiogenic syncope, seen most frequently in patients who are standing. The blood pressure or heart rate (or both) may drop precipitously and recover again when lying supine. Orthostatic hypotension due to medications, toxic-metabolic issues from electrolyte shifts (e.g., hypoglycemia), and bradyarrhythmias may also present as syncope. Rarer causes of more lethal syncopal forms may include tachyarrhythmias due to ventricular fibrillation from a cardiomyopathy, coronary artery disease, or genetic causes such as Brugada or long QT syndrome.
Evaluation of Syncope
Guidelines for the diagnosis and management of syncope were published in 2009 and endorsed by both the European Society of Cardiology and Heart Rhythm Society.3 The guidelines recommend performing a detailed physical exam with carotid sinus massage and checking for orthostatic vital signs, which were normal in this patient. His EKG showed a left bundle branch block (LBBB). The LBBB on EKG led to an echocardiogram, which was normal. A head-up tilt table test with IV isoproterenol was normal, which did not exclude the diagnosis of vasovagal syncope. A 24-hour Holter monitor was also unrevealing.
We did not get a stress test in this patient since the syncopal event did not occur in association with exercise.3 The neurologist recommended an EEG (for seizures), a head CT, and a carotid ultrasound, although these diagnoses seemed unlikely (there was no history of a head injury). Fortunately, all of these tests were normal. We also performed an EP study looking for prolonged HV intervals, tachyarrythmias that could be ablated, long sinus pauses, or ventricular arrhythmias, but the test was normal.
Syncope While Driving: Literature Review
There is little literature examining the causes and long-term outcomes of patients who have had syncope while driving, particularly in a healthy patient described here who does not have a cardiomyopathy.4,5
Researchers at the Mayo Clinic retrospectively looked at 381 patients from their large database over a two-year period (1996-1998) who had syncope while driving.4 The mean age at the time of the syncopal event was 56 years old, and most (65%) were male. Roughly one-quarter of the patients had a “cardiac history,” and 82% had previous syncopal episodes. Almost one-third were injured as a result of the index syncopal event. In the end, the diagnosis of the syncope was “vasovagal” in 37%, with another 24% ultimately having no diagnosis ever identified.
We do not know exactly from this study what tests were done for each patient. Certainly an implantable loop recorder was probably not placed in each patient since its usage was not as widespread as today. Thus, it is possible that some of the patients presumptively labeled as having “vasovagal syncope” actually had a bradyarrhythmia that was never documented (and therefore was never treated).
The patients in this Mayo Clinic study did well long term. There was no increased mortality rate for those patients who had syncope while driving compared with similar syncopal patients who were not driving at the time of their episode. The chance of recurrence for syncope during driving was 0.7% at 6 months and 1.1% at 12 months; chances of recurrent syncope at all (but not during driving) was 12% at 6 months and 14.1% at 12 months.
The authors in the Mayo Clinic study discuss driving recommendations following syncopal events. They concur with the concept of waiting 3 to 6 months in such patients before resuming driving, but they emphasize that each patient must be carefully evaluated on an individual basis. Their paper would suggest that waiting 6 months before allowing such patients to drive would be a reasonable time frame.4
In addition, a study from Italy looked at the follow up for patients who experienced syncope while driving.5 The authors prospectively studied 90 patients referred to the University of Padua Medical Center in Italy for syncope. Forty patients had syncope while driving, and a control cohort of 50 patients had syncope in other circumstances. For evaluation, patients underwent carotid sinus massage, a Holter monitor with heart rate variability analysis, and an upright tilt table test. Almost 70% in both groups had a positive tilt table test. The researchers noted that patients who experience syncope while driving generally have a favorable prognosis.
There are guidelines barring driving for private use in patients who have received an implantable cardioverter defibrillator (ICD).6 In patients who received an ICD for primary prevention, they should not drive for one month (European Heart Rhythm Association) or one week (American Heart Association). This suggestion is so that the ICD implant can heal. Currently, professional drivers (e.g., commercial truck drivers) are permanently barred from driving with an ICD implant. However, these are patients who have not necessarily had a syncopal event, as in the patient described here.
Thus, it is generally suggested that patients without a defibrillator refrain from driving 3 to 6 months after a syncopal event while driving, but there is no hard rule that guides us in that regard.
Use of ILRs in Syncope
The use of implantable loop recorders (ILRs) in the evaluation of syncope has been well documented. Therefore, we will touch only briefly on this topic since it is beyond the narrow scope of our article.
The PICTURE (Place of Reveal in the Care Pathway and Treatment of patients with Unexplained Recurrent Syncope) registry was a prospective study conducted in 11 countries using ILRs to evaluate 570 patients with unexplained syncope.7 Almost 40% of the patients had at least one syncopal event over the roughly 10-month follow-up period. Of those patients, 170 (or 78%) had the event documented on the ILR, which led to a diagnosis for the syncopal events. Over half (51%) had bradyarrhythmias or pauses, leading to insertion of a pacemaker. At the end of the study period, 18% still had no diagnosis on the ILR for their unexplained syncopal spells.
The European Heart Rhythm Association recommends the use of ILRs in patients who have recurrent syncope of uncertain origin (Class I recommendation).3
Based on these findings, we decided to implant an ILR in our patient, since all of his tests were completely normal and we still had no diagnosis for his syncope.
There are no absolute contraindications for patients to cease driving after a syncopal event that occurs while driving. However, most physicians would restrict driving in these patients for 3 to 6 months if no etiology for the syncope was found. The restriction may be shorter if a cause of the syncope is identified and treated. The long-term prognosis for such patients is generally excellent.
Because all of the tests were unrevealing in this patient’s case, we implanted an ILR and allowed him to drive after 6 months without syncopal episodes. We checked the ILR at regular intervals, and it never showed any pauses or arrhythmias.
At the 10-month mark post-ILR implant, the patient called us from rural Nevada, where he had again blacked out at the wheel while driving and crashed his car. Incredibly, he was again unharmed. Interrogation of the ILR demonstrated a 10-second asystolic pause (for no clear reason; he was not on any medications). We removed the ILR and placed a dual chamber pacemaker.
We advised the patient not to drive for a year. At the one-year mark post-pacemaker implantation, there were no further syncopal events, and he resumed driving. So far, so good.
- Kapoor WN. Syncope. N Engl J Med 2000;343:1856–1862.
- Soteriades ES, Evans JC, Larson MG, et al. Incidence and prognosis of syncope. N Engl J Med 2002;347:878–885.
- Moya A, Sutton R, Ammirati F, et al. Guidelines for the diagnosis and management of syncope. Eur Heart J 2009;30:2631-71.
- Sorajja D, Nesbitt GC, Hodge DO, et al. Syncope while driving: Clinical characteristics, causes, and prognosis. Circulation 2009;120:928–934.
- Folino F, Migliore F, Porta A, et al. Syncope while driving. Auton Neurosci 2012;166:60–65.
- Thijssen J, Borleffs CJ, van Rees JB, et al. Driving restrictions after implantable cardioverter-defibrillator: An evidence-based approach. Eur Heart J 2011;32:2678–2687.
- Edvardsson N, Frykman V, van Mechelen R, et al. Use of an implantable loop recorder to increase the diagnostic yield in unexplained syncope: Results from the PICTURE registry. Europace 2011;13:262–269.