Correspondence

Driving after Life-Threatening Ventricular Tachyarrhythmia

N Engl J Med 2002; 346:208-209January 17, 2002

Article

To the Editor:

Akiyama and coworkers (Aug. 9 issue)1 claim that motor vehicle accidents are no more common, or possibly less common, among patients who resume driving after ventricular tachyarrhythmias than in the general driving population. The reported annual risk was 3.4 percent, lower than the estimate for the general population. However, only 559 of 1016 of all patients originally enrolled in the study group (55 percent) responded to the question regarding injuries from automobile accidents. As pointed out in the accompanying editorial,2 107 patients died before completing the questionnaire; this group may have included persons who died from injuries incurred in motor vehicle accidents. Furthermore, it is reasonable to assume that injury-free patients would be overrepresented in the group that responded.

There is another important bias to be considered. The source quoted for national injury rates is based on data from police accident reports. Approximately two thirds of these reports are generated because of property damage only and not because of injuries or deaths. The drivers in this study would have had strong reasons to avoid reporting vehicle crashes that resulted only in property damage, especially if physicians had expressed concern about their driving ability.

Albert B. Lowenfels, M.D.
New York Medical College, Valhalla, NY 10595
lowenfel@nymc.edu

2 References

1. 1

   Akiyama T, Powell JL, Mitchell LB, Ehlert FA, Baessler C. Resumption of driving after life-threatening ventricular tachyarrhythmia. N Engl J Med 2001;345:391-397
   Full Text | Web of Science | Medline

2. 2

   Smith TW. Driving after ventricular arrhythmias. N Engl J Med 2001;345:451-452
   Full Text | Web of Science | Medline

To the Editor:

In their study, Akiyama et al. do not provide data about the driving environments of the study population before the arrhythmic event. It should be anticipated that patients who have experienced a life-threatening arrhythmia will avoid (consciously or unconsciously) exposing themselves to demanding driving conditions (such as driving at rush hour or on highways). In this case, a low accident rate results from the change of driving environment and underestimates symptomatic arrhythmic events (which occurred in every third patient in the study) as factors that abruptly disturb driving capacity. This interpretation is supported by the paradox that the annual rate of motor vehicle accidents among the study patients was 1.8 times higher before the index episode of ventricular tachyarrhythmia than it was after the episode (6.2 percent vs. 3.4 percent).

Haralampos Kriatselis, M.D.
Konrad Göhl, M.D.
Martin Gottwik, M.D.
Klinikum Nürnberg, 90471 Nuremberg, Germany
kriatselis@t-online.de

Author/Editor Response

The authors reply:

To the Editor: Lowenfels correctly identifies a limitation of our report. As we stated, the questionnaire-based method relies, of necessity, on the cooperation, understanding, truthfulness, and memory of potential participants. However, no other study method would provide the critical information required to assess the true risk of permitting patients who are subject to sudden incapacitation due to medical conditions to drive. A previous report on the same study population1 supports our belief that the questionnaires were being answered truthfully, because the correlation between a report by the study coordinator of a patient's driving status and that patient's own report of his or her driving status was very high.

Furthermore, Lowenfels's concern is overstated when he indicates that only 559 of the 1016 patients in the study (55 percent) responded to questions regarding motor vehicle accidents. A substantial proportion of the patients who did not respond to these questions did not have the opportunity to do so, since they were not driving either by choice or because they had died. Instead, 559 of the 563 living patients who indicated that they were driving (99 percent) responded to questions regarding motor vehicle accidents. The sensitivity analysis indicated that the vast majority of patients who did not respond to the questionnaires or who responded to the questionnaires but did not answer the question regarding motor vehicle accidents would have to have had an accident to invalidate the major conclusions of the study. We consider this to be improbable. With regard to Lowenfels's suggestion that some patients may not have responded because they had already died in motor vehicle accidents, the causes of death of all study patients were adjudicated by the main study-events committee, and no deaths resulted from motor vehicle accidents.

Kriatselis et al. indicate that the low accident rate for the patients in this study may have resulted from a self-imposed restriction of their driving to less demanding environments. Because we did not collect information related to driving environments before each patient's ventricular tachyarrhythmic event, we cannot determine whether the hypothesis of Kriatselis et al. is or is not true. Nevertheless, we agree that the hypothesis is possible and warrants further study.

Toshio Akiyama, M.D.
University of Rochester Medical Center, Rochester, NY 14642

Judy L. Powell, B.S.N.
University of Washington, Seattle, WA 98105-4689
avidctc@u.washington.edu

L. Brent Mitchell, M.D.
University of Calgary, Calgary, AB T2N 2T9, Canada

1 References

1. 1

   Hickey K, Curtis AB, Lancaster S, et al. Baseline factors predicting early resumption of driving after life-threatening arrhythmias in the Antiarrhythmics Versus Implantable Defibrillators (AVID) Trial. Am Heart J 2001;142:99-104
   CrossRef | Web of Science | Medline