Cardiac risk of speed traps

Automatic implantable cardioverter defibrillator rhythm strip data as used in interpretation of a motor vehicle accident

The automatic implantable cardioverter defibrillator (AICD) is an electronic device that monitors the rhythm of the heart and, upon detecting a life-threatening arrhythmia, shocks the heart in an attempt to restore a normal rhythm. The AICD will electronically store the information of the event. Later, the AICD can be "interrogated" and the information electronically retrieved, with a printout of the rhythm strip obtained. The interrogation is fairly simple and involves a magnetic device placed over the AICD, which in turn is connected to a portable computer, which, with specialized software, can deliver the information in a usable form. Not only can information about the most recent shock be obtained, but also information about previous shocks can be retrieved. This case presentation highlights how such preterminal information retrieved from an AICD helped to interpret the circumstances leading to a death--in this case, a fatal motor vehicle accident. Additionally, driving restrictions that may be placed on individuals with AICDs are discussed.

Effects of mental stress on brachial artery flow-mediated vasodilation in healthy normal individuals

BACKGROUND

Mental stress is associated with increased risk for cardiovascular events, possibly because of acute increases in endogenous catecholamines. Recently, brachial artery flow-mediated vasodilation has been used for noninvasive assessment of macrovascular endothelial function. The effect of mental stress and its associated changes in sympathetic activation on brachial artery endothelium-dependent vasomotor tone in vivo remains unknown.

METHODS AND RESULTS

Two-dimensional ultrasound was used to measure brachial artery flow-mediated vasodilation before and after mental stress (provoked by a standard arithmetic challenge) in 21 healthy individuals (10 men, 11 women; average age 23.5 years). The flow stimulus resulted from a 3-minute cuff occlusion of distal forearm blood flow, causing distal hyperemia and a transient 2- to 3-fold increase in brachial artery blood flow on cuff release. During mental stress, heart rate increased on average by 29.6% and blood pressure increased on average by 17.9%. The sympathetic stimulus resulted in a 64% average increase in flow-mediated vasodilator response (P <.001). The enhanced vasodilator response during mental stress was similar for men and women.

CONCLUSIONS

Mental stress can have marked effects on endothelium-dependent, flow-mediated vasodilation in healthy, normal individuals. Similar studies in individuals with impaired endothelial function may further our understanding of the role of mental stress in the development of cardiovascular events.

Life stress, social support and coronary heart disease

OBJECTIVE

The aim of this paper is to review the relationship between life-event stress, social support and coronary heart disease.

METHOD

A literature search from 1978 to early 1999 using Medline, PsychINFO and EMBASE databases was performed. It focused largely on prospective studies.

RESULTS

Both life-event stressors and inadequate social supports assessed by a variety of indicators are risk factors for acute coronary heart disease events. Poor social support does not particularly appear to moderate the relationship of life stress to coronary heart disease but rather both appear to be independent risk factors.

CONCLUSION

While life-event stress and poor social supports are risk factors, the exact mechanism by which they impact on heart disease is not as yet well elicited, although disturbance in mood would appear to be the most likely intervening variable.

The acceptable risk of driving after myocardial infarction: are bus drivers a special case?

BACKGROUND

Bus drivers frequently encounter difficulty in returning to their former employment after recovery from myocardial infarction. The risk that a recurrence of myocardial infarction may cause a personal-injury accident is analyzed.

METHODS

The Cumulative Medical Index and Current Contents was searched systematically from 1980 to date, accepting papers irrespective of language. Relevant earlier material was drawn from the author's published reviews on bus driving and myocardial infarction and vehicle accidents. One hundred twenty-three articles were included in the database, of which 110 were used in the review.

RESULTS

The risk of a personal injury accident or fatality from a sudden cardiovascular incident is calculated as the product of typical driving time per day (Td = 0.167), vehicle characteristics (V) (a low factor of 0.167 for an urban bus because of slow speed and use of reserved curb lanes), the risk of recurrence of a sudden cardiovascular incident (SCI) (.015, somewhat greater in bus drivers than in the general population), and the risk that such an incident will cause a personal-injury accident (Ac) (at 0.005, probably lower than in the general population because of low vehicle speeds and the bus driver's experience in defensive driving).

CONCLUSIONS

The overall risk is 0.00002, 1 in 50,000 driver-years, is lower than accepted for passenger-car operators, and only slightly greater than for the older symptom-free adult. Bus drivers who meet the current standards of the Canadian Cardiovascular Society should be encouraged to return to their former employment.