Buffl

Cardiology

BS
by Brett S.

Hazardous substances and RTW following ACS

Work involving exposure to certain hazardous substances may aggravate pre-existing CHD and careful consideration should be given to patients who are returning to work involving exposure to chemical, gases, and pollutants. Methylene chloride, an ingredient of many commonly used paint removers, is rapidly metabolized to carbon monoxide in the body; in poorly ventilated areas, blood levels of carboxyhaemoglobin can become high enough to precipitate angina or even MI (impairment of cardiovascular function begins at a blood carboxyhaemoglobin level of 2–4%). Careful assessment taking account of the total exposure to carbon monoxide (active/passive smoking, air pollutants/chemicals) and correlation against symptoms of chest pain will allow a pragmatic approach to risk assessment in these rare cases. Smokers, especially pipe smokers, will have an elevated blood carboxyhaemoglobin, which is additive to carbon monoxide in the workplace, potentially increasing their risk of adverse cardiac events. The World Health Organization (WHO) recommends a maximum carboxyhaemoglobin level of 5% for healthy industrial workers and a maximum of 2.5% for susceptible persons in the general population exposed to ambient air pollution. This level may also be applied to workers whose jobs entail exposure to carbon monoxide (e.g. car park attendants and furnace workers). There is a good correlation between carbon monoxide levels in air and blood carboxyhaemoglobin levels, in accordance with the Coburn equation. To ensure that the 2.5% carboxyhaemoglobin level is not exceeded, the ambient carbon monoxide concentration should not be higher than 10 ppm over an 8-hour working day— equivalent to exposure at 50 ppm for no more than 30 minutes.

Solvents, such as trichloroethylene or 1,1,1-trichloroethane, may sensitize the myocardium to the action of endogenous catecholamines resulting in ventricular fibrillation and sudden death in workers with high exposure.

Chlorofluorocarbons (CFCs) have been used as propellants in aerosol cans and as refrigerants. CFC-113 has been implicated in sudden cardiac deaths and CFC-22 has been reported to cause arrhythmias in laboratory workers using aerosols.

Pacemakers and RTW/FFD

The presence of an implanted cardiac pacemaker to maintain regular heart action is entirely compatible with normal life, including strenuous work. The underlying heart condition for which the pacemaker was implanted may, however, impose its own restrictions. Virtually all pacemakers have the capacity to sense and can be inhibited by the patient’s own heart rhythm. Somatic muscle action potentials and electromagnetic fields can in theory interfere with the pacemaker, causing temporary cessation of pacing.


Electromagnetic interference can occur due to conducted or radiated electromagnetic energy.28 Industrial electrical sources such as arc welding, faulty domestic equipment, engines, antitheft devices, airport weapon detectors, radar, and citizen-band radio, all generate electromagnetic fields that can, in theory, affect pacemakers and ICDs. Any pacemaker abnormality is usually confined to one or two missed beats or reversion to the fixed mode. ICD discharges are equally rare. However, both pacemakers and ICDs have been designed to have a high degree of tolerance to electrical and magnetic interference fields, and special filtering components have been incorporated to minimize the effects. If pacemaker patients are expected to work in the vicinity of high-energy electromagnetic fields capable of producing signals at a rate and pattern similar to a QRS complex (e.g. on some electrical generating and transmission equipment and welding) then formal testing is recommended.

Author

Brett S.

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