Acute coronary syndromes occurring while driving: frequency and patient characteristics

Acute coronary syndrome (ACS) may occur during any human activity, including driving [1‐3]. The objectives of this study were to report the frequency and patient characteristics of ACS occurring while driving. An effort was made to identify variables associated with ACS occurring while driving. Furthermore, the behavioral patterns of afflicted drivers were analyzed to clarify relationship between ACS and automobile accidents.

This was a single-center, retrospective observational study conducted using prospectively acquired data. The study protocol was approved by our institution’s ethics committee. ACS was defined as the presence of either ST-segment elevation myocardial infarction (STEMI), non-ST-segment elevation myocardial infarction, or unstable angina pectoris [4]. ACS was generally treated according to the recent guidelines [5]. After arrival in the emergency department (ED), the temporal sequence of resuscitative events was recorded on an integrated clinical database CAP-2000 (Nihon Kohden, Tokyo, Japan) by ED residents. Detailed information on when, where, and how the patients’ symptoms developed was obtained from patients, surrogates, or paramedics. They were also asked about activities performed immediately before symptom onset. We modified the classification of daily activities by Hayashi et al., in which the activities were classified into eight categories (sleeping, resting, eating, walking, hard working, bathing/toilet, driving, and other activities) [6, 7].

Unless contraindicated, patients suspected of ACS routinely underwent contrast-enhanced whole-body computed tomography to rule out aortic dissection. Patients diagnosed with ACS were brought to a catheter lab for possible percutaneous coronary intervention (PCI). We used a dataset of 1605 newly diagnosed ACS patients, aged ≥ 18 years, who were admitted to our institution between January 2011 and December 2016. Patients who drove to our institution with symptoms that had occurred while performing other activities as well as those with stable angina pectoris who noticed chest pain while driving were excluded from analysis. Geriatric patients who were transferred from nursing care facilities were also excluded.

Acute cardiovascular events occurring while driving have been studied relatively frequently [1‐3]. However, most of those studies were conducted by either forensic scientists or crash scene investigators, and only drivers whose cardiovascular events led to loss of consciousness and subsequent automobile accidents have been evaluated [1‐3]. In this context, the present study was unique as it focused on all patients who sustained ACS while driving. The frequency of ACS occurring while driving in our cohort, consisting of adults who led independent lives, was 4.0%. There was a marked circadian variation in the frequency of ACS occurring while driving, with more than 50% of drivers experiencing symptoms in the morning (Fig. 2). While this may have been simply because traffic volume was heavy with commuters in the morning, it may have also reflected the fact that ACS in itself is most likely to occur in the morning [9].

It is likely that ACS occurred while driving merely by chance in the great majority of patients. In other words, causality between driving and ACS is mostly questionable. Nevertheless, demographic comparison (Table 1) as well as multivariable regression analysis (Table 2) suggests that current smoking may be a risk factor for ACS occurring while driving. Smoking promotes hypercoagulability via the action of carbon monoxide [10]. In addition, drivers sit in a confined space in the same posture for hours, and uninterrupted sitting while driving per se may be associated with hypercoagulability [11‐14]. Furthermore, drivers may become dehydrated after driving for hours without drinking water. Higher BMI in the afflicted drivers (Table 1) also suggests that underlying obesity may have some role in the causation of ACS occurring while driving. Taken together, combination of these adverse factors may result in thrombosis of the coronary arteries and ACS. In addition to current smoking, age was correlated with ACS: younger adult drivers might be more likely to sustain ACS than their elderly counterparts (Table 2). However, interpretation of this finding requires caution, because driving, smoking habit, and aging process is complicatedly intertwined: the elderly generally drives less frequently and for shorter distances than the younger population, and the smoking rate drops as age advances [15, 16]. Male sex was not associated with ACS (Table 2), and it remains unclear whether gender difference influences the likelihood of developing ACS while driving. Nevertheless, male smokers may be at increased risk for ACS while driving (Additional file 1: Table S1). The fact that women drive less often and cease driving earlier than men should also be considered in interpreting the marked male preponderance of 92% (Table 1) [17]. Based on these findings, smoking cessation is advised for drivers who smoke from a standpoint of driving safety. A recent study showing the efficacy of smoking ban in the reduction of ACS suggests that regulations to limit the use of cigarette while driving may be worth consideration [18].

Regarding the relationship between ACS and automobile accidents, the majority of drivers who sustained ACS kept driving without accidents and managed to reach medical facilities (Fig. 1). By contrast, all 10 patients who sustained cardiac arrest while driving caused automobile accidents. It is likely that loss of consciousness after cardiac arrest resulted in loss of control of vehicles and accidents. We expect that devices to enable earlier detection of driver deterioration are installed in future vehicles to prevent or reduce automobile accidents.

There are limitations to the present study. First, sample number was relatively small due to the single-center retrospective study design. Moreover, this was not a population-based study, and the incidence of ACS occurring while driving remains unknown. Second, the information on the temporal relationship between driving and onset of symptoms, mostly acute chest pain, was mostly obtained from the patients themselves, indicating the possibility of a recall bias. Finally, despite the apparent adverse effects of smoking, information on the quantity of cigarettes consumed by drivers was not always collectible. It was also unclear how many drivers sustained ACS while they were smoking in their vehicles. Despite these limitations, the present study is probably the first to document the frequency and patient characteristics of ACS occurring while driving. As the elderly population grows rapidly, the incidence of ACS occurring while driving may also increase worldwide. Prospective multicenter studies should be conducted to identify individuals at risk for ACS while driving.