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The impact of coronary heart disease on life and work 

The impact of coronary heart disease on life and work
Chapter:
The impact of coronary heart disease on life and work
Author(s):

Michael C. Petch

DOI:
10.1093/med/9780199204854.003.161308_update_002

Update:

This chapter has been retired and will not be updated further. The subject matter of this chapter is to be found in chapters 16.13.4, 16.13.5, 16.13.6, and 16.13.7 of this online update.

Updated on 29 October 2015. The previous version of this content can be found here.
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date: 21 November 2019

Essentials

Coronary heart disease is common and lethal: these facts are well known and have a profound influence on attitudes of victims and others—their families, friends, and employers.

The presence of heart failure and/or significant areas of cardiac ischaemia is the principal determinant of prognosis, and can be best judged by history, examination, and noninvasive testing, with common sense and experience being the best tools for assessing an individual’s fitness to resume life and work following the development of coronary heart disease.

Following a cardiac event such as myocardial infarction or coronary artery bypass grafting, patients with an acceptable exercise response are often enrolled into a rehabilitation programme. Following myocardial infarction or unstable angina, those with no complications and good exercise tolerance may return to work in about 4 weeks.

The risk of sudden disability and death through ventricular fibrillation is the major factor affecting work capacity amongst victims of coronary heart disease. Workers whose sudden incapacity would place themselves and others at risk are described as being in ‘safety-critical’ jobs. The best approach to determine whether someone should be able to return to work is to define what level of risk is acceptable, and then decide whether their medical condition places them within the predetermined limits of acceptability. The Civil Aviation Authority was the first to adopt this approach with what is now known as the ‘1% rule’, based on assumptions and calculations indicating that a pilot with a 1% annual risk of a cardiac event has the same risk of ‘failing’ when flying as other elements of the aircraft.

Ordinary driving may be resumed 1 month after a cardiac event, provided that the driver does not suffer from angina that may be provoked at the wheel. Vocational driving may be permitted at 6 weeks, subject to a satisfactory outcome from noninvasive testing.

Despite modern treatments, some patients will experience multiple coronary events that eventually lead to extensive ventricular damage: they—with their partners, if appropriate—should be given the opportunity of a frank discussion about their prognosis, but some would rather not know and that attitude should be respected.

Introduction

Coronary heart disease is common and lethal (Tables 16.13.8.1 and 16.13.8.2). In developed countries, heart attacks account for about one-quarter of all deaths. Death is often sudden. These facts are well known and have a profound influence on attitudes towards the victims of heart disease. Employers are reluctant to take back people who have lost time off work as a result of a heart problem. Spouses become overprotective. The survivors are acutely aware that they have received an intimation of their mortality; some fail to cope. The first manifestation of coronary heart disease, which is usually chest pain, prompts re-evaluation of the remainder of life and work. The spectre of cardiac pain and death hangs over many a middle-aged man, including employers, politicians, public health physicians, journalists, and others in positions of influence. In most developed countries there is therefore public pressure to prevent the development of coronary disease (primary prevention), to prevent a recurrence (secondary prevention), and to put in place measures that will reduce the risk of harm to the individual and others in the event of sudden incapacity/death of a worker in a ‘safety-critical’ job.

The impact of coronary heart disease on life and workTable 16.13.8.1 Deaths by cause, sex, and age, 2006, United Kingdom

All ages

Under 35

35–44

45–54

55–64

65–74

75+

All causes

Men

276 725

9 011

7 519

14 420

31 406

55 445

158 924

Women

302 952

4 878

4 446

9 680

21 060

39 496

223 392

Total

579 677

13 889

11 965

24 100

52 466

94 941

382 316

All diseases of the circulatory system (I10–I99)

Men

91 645

547

1 482

4 214

9 431

17 785

58 186

Women

99 212

295

593

1 535

3 794

10 026

82 969

Total

190 857

842

2 075

5 749

13 225

27 811

141 155

Coronary heart disease (I20–I25)

Men

49 665

118

787

2 739

6 317

10 889

28 815

Women

38 571

23

192

590

1 742

4 861

31 163

Total

88 236

141

979

3 329

8 059

15 750

59 978

Stroke (I60–I69)

Men

20 357

113

223

570

1 244

3 004

15 203

Women

22 785

84

183

463

949

2 413

18 693

Total

43 142

197

406

1 033

2 193

5 417

33 896

Notes: ICD codes in parentheses.

Source: England and Wales, Office for National Statistics (2010) personal communication. Deaths registered by cause, sex and age. www.statistics.gov.uk (accessed April 2010).

Scotland, General Register Office (2010) Registrar General Report. GRO: Edinburgh.

Northern Ireland, General Register Office Statistics and Research Agency (2008) Registrar General Annual Report. NISRA: Belfast.

The impact of coronary heart disease on life and workTable 16.13.8.2 Inpatient cases by main diagnosis and sex, National Health Service hospitals, 2006/07, England and Scotland

England

Scotland

Wales

Men

Women

Men

Women

Men

Women

All diagnoses

7 145 742

9 086 837

656 837

735 320

402 707

505 134

All diseases of the circulatory system (I00–I99)

741 384

580 911

81 519

64 889

46 544

37 543

Coronary heart disease (I20–I25)

274 163

148 171

31 884

17 620

17 614

9 726

Angina pectoris (I20)

67 219

48 846

7 164

5 469

4 011

3 069

Acute myocardial infarction (I21)

65 060

41 119

12 301

7 169

4 118

2 773

Other coronary heart disease (I25)

141 884

58 206

12 419

4 982

9 485

3 884

Heart failure (I50)

54 503

52 305

6 131

5 360

4 151

3 791

Stroke (I60–I69)

91 363

98 738

10 612

11 321

5 995

6 829

Notes: Finished consultant episodes; ordinary admissions and day cases combined.

Pregnancy cases are not included. ICD codes (10th version) in parentheses.

Source: Department of Health (2009) Hospital Episode statistics 2008/09. www.hesonline.nhs.uk (accessed May 2010)

Information services Division Scotland (2009) Main diagnosis discharges from hospital 2007/08. www.isdscotland.org (accessed May 2010)

Health Solutions Wales (2009) Primary Diagnosis – 2008/09 www.infoandstats.wales.nhs.uk (accessed Aug 2010).

Women are not immune, but for them coronary heart disease tends to strike later, often after usual retirement age. Nevertheless, the impact of coronary heart disease can be as devastating: older women are often the most important carers in a family. Although there are minor differences between the sexes in the presentation and management of coronary heart disease, the comments in this chapter should be taken to apply to both sexes.

Life before coronary heart disease

Most people do not think about their health until it goes wrong. With advancing years people become aware that their contemporaries are suffering from mortal diseases and belatedly begin to look at their own lifestyle. Many believe the results of the latest research quoted in the press and attempt to adapt their habits by increasing their intake of vitamin E, or fish oil, or red wine, or by reducing the amount of coffee and animal fat that they consume, or by undergoing stress counselling, or by purchasing an exercise machine that they never use. Then along comes a new report and another fashion is spawned.

There are a few public health issues on which the medical profession can speak with authority. Cigarette smoking is the prime example. Doctors, nurses, and other health care professionals have a duty to discourage this habit by example and by persuasion. No other habit enjoys such powerful evidence that mandates a lifestyle change. Regular exercise is to be commended. A prudent diet is capable of different interpretations, but the old adage ‘a little of what you fancy does you good’ dates back many generations to a time when coronary heart disease was much less common. Food can be one of life’s great pleasures. The current political ambition to change national lifestyles is not heeded by those most at risk and has never been clearly shown to have lasting benefit.

A sensible compromise for most societies is to prevent smoking, encourage exercise, promote the sale of fruit and vegetables, and reduce the availability of junk foods in shops and workplace canteens, but not to go to such lengths that people feel guilty when faced with a delicious steak. The fact that most doctors share this epicurean attitude makes it all the more persuasive. The use of drugs such as aspirin and statins to reduce the risk of a coronary event can likewise only be justified in those individuals whose risk is especially high, as judged by their family history and other risk factors.

Health screening is another controversial topic. In (over)-developed societies screening services have become very popular and assessment of cardiovascular risk in businessmen is a useful source of income for some clinics. Certainly the measurement of blood pressure can be supported and, in some circumstances, the estimation of serum lipids. Beyond that the advice that may be offered boils down to common sense—don’t smoke, take more exercise, and eat less.

Health screening nowadays commonly includes exercise testing with ECG monitoring. False-positive results suggesting silent coronary disease occur in up to 15% of middle-aged people, depending upon the criteria used. The psychological effect can be devastating. This investigation can only be justified when the individual is aware of the possible outcomes of screening and/or is in a safety-critical job. The ability of CT to detect coronary disease has further complicated this area of medical practice: it is readily available to those who are prepared to pay, and the subsequent management of those individuals is uncertain because long-term follow-up of those with abnormal findings is not available. The radiation exposure means that the investigation should not be undertaken without due consideration. The finding of an abnormality is particularly difficult to interpret and has prompted the aphorism ‘the normal person is merely the one who has not been adequately investigated’.

Life and work with coronary heart disease

The risk of sudden disability and death through ventricular fibrillation is the major factor affecting work capacity amongst victims of coronary heart disease. The risk is greatest in the early days following the development of symptoms and in those with most extensive coronary disease and/or with most myocardial damage.

Common sense and experience (i.e. clinical judgement) remain the best tools for assessing an individual’s fitness to resume life and work following the development of coronary heart disease. The onset of cardiac pain, or change in the nature of pain in someone with known ischaemic heart disease, should prompt rapid evaluation. Stable angina pectoris, preferably confirmed by exercise testing, usually requires no change in lifestyle: modern drug therapy is very effective and often comprises just aspirin, glyceryl trinitrate, and a statin. Unstable angina or myocardial infarction is a different matter and necessitates hospital admission, with further investigation including coronary angiography. Specialist opinion remains the basis for advice about lifestyle changes, supplemented by the results of the investigations.

The presence of heart failure and/or significant areas of ischaemia are the principal determinants of prognosis. The former may be identified by history, clinical examination, chest radiography and echocardiography; the latter by the development of angina and electrocardiographic ST segment shift on exercise testing. An exercise test may also reveal cardiovascular incapacity in other ways, e.g. exhaustion, inappropriate heart rate and blood pressure responses, and arrhythmia.

ST segment elevation myocardial infarction (STEMI) is best managed by emergency angiography and ‘primary PCI’ (see below); non-STEMI or unstable angina (aka acute coronary syndrome or ACS) is likewise best managed by urgent angiography and, usually, PCI (see Chapter 16.13.5). Subsequent assessment of prognosis along the lines outlined above is recommended: those with no complications and good exercise tolerance may return to work in about 4 weeks. This applies particularly to younger individuals whose employers need have little hesitation in taking them back to their former job, perhaps part-time initially. A few will take longer to recover, and some will need a change of job.

Limitation of working capacity and the risk of sudden incapacity can both be well judged in populations by specialist opinion, aided by the results of investigations, particularly the coronary anatomy and left ventricular function. However, the progression of coronary disease can be unpredictable, and individuals judged to be at low risk from further cardiovascular events can suffer recurrences. This difference between the individual and the population is not well understood by employers and employees and can be a source of misunderstanding and confusion. Nevertheless, individual exceptions do not invalidate the principles on which recommendations are made.

Percutaneous coronary intervention (PCI)

The number of PCI procedures in the UK continues to grow, with most of that growth being the treatment of emergencies. Patients with persistent angina, or those with a very abnormal exercise response, should undergo coronary arteriography with a view to myocardial revascularization, i.e. elective PCI or CABG. PCI invariably nowadays involves the insertion of a stent and is a straightforward, safe procedure that can be very effective in relieving angina. Resumption of normal activities, including work, is normally possible a few days afterwards. Following primary PCI, a further elective procedure may be required for any untreated stenosis. Recurrent angina is much less common with the more widespread use of drug-eluting stents, which have reduced the risk of restenosis almost to zero. There is a small risk of late stent thrombosis, but the absolute risk is so small that there should be no significant impact on lifestyle and ability to work. Following elective PCI recovery is rapid and most people are back at work within a few days.

The impact of coronary heart disease on life and workThe success of primary PCI will mean that guidelines concerned with the resumption of normal activities following a coronary event, e.g. work and travel, are likely to recommend even shorter periods of convalescence. This is both because recovery times are shorter than with previous therapy and because the state of the coronary arteries and left ventricle are known, hence further investigation is superfluous.

Coronary artery bypass grafting (CABG)

Coronary artery bypass grafting is also remarkably safe, with most centres reporting mortality rates of less than 1% for elective operations. Recovery is rapid and most patients resume work within 2 to 3 months of surgery. Almost all are relieved of their angina. Patients who were able to work before surgery should generally be able to do so afterwards, and restrictions that may have been appropriate previously should no longer be relevant. However, since surgery is a dramatic event, it may prompt overprotective attitudes amongst family members, friends, employers, or even medical advisers. Many individuals who could and should return to work fail to do so for this reason, rather than because of continuing incapacity. No special restrictions are usually necessary after return to work. Coronary graft stenosis and occlusion leads to recurrence of angina at a rate of about 4% per year. This is generally less severe than previously but will affect long-term occupational planning. The short recovery times, safety, and efficacy of PCI has meant that this procedure is the preferred method of myocardial revascularization, with approximately five times as many procedures being performed in most developed countries; 87 676 PCI procedures as compared with 17 822  bypass operations in the United Kingdom in 2010.

Rehabilitation programmes

Rehabilitation programmes are now well established in many hospitals and communities. These enable patients to make a full physical and psychological recovery following a cardiac event such as myocardial infarction or coronary artery bypass grafting. An acceptable exercise response is a prerequisite for enrolment into a rehabilitation programme. The participants are thus the fittest survivors, selected for physical retraining on the strength of their satisfactory performance on the treadmill. Definite measures of benefit, such as reduction in recurrent myocardial infarction or death, are lacking.

The popularity of cardiac rehabilitation owes much to the enthusiasm of the participants—patients and staff alike—but may also be a reflection of modern cardiological practice with its mechanistic approach, haste, and failure to recognize the psychological and lifestyle implications of a diagnosis of heart disease. Sex, for example, is rarely discussed except in rehabilitation classes, yet for many patients it is a burning issue. The mechanistic view is that the physical effort required is equivalent to two flights of stairs or stage 3 of the Bruce protocol; the psychological aspects are less easy to quantitate.

Risk evaluation

The 1% rule

Workers whose sudden incapacity would place themselves and others at risk are described as being in ‘safety-critical’ jobs. The traditional approach to this dilemma was to exclude anyone with heart disease from working in such an environment. This may still be appropriate in occupations where any increased risk of incapacity is unacceptable: drivers of mainline passenger trains and captains of ocean-going vessels are two current examples. However, this blanket exclusion is patently unfair to some, and may waste the skills and experience of a valued employee. Also, no individual is totally free of risk of an incapacitating event, and a few accidents as a result of sudden illness in apparently normal people are inevitable.

A better approach is to define what level of risk is acceptable, and then decide whether the medical condition places an individual within the predetermined limits of acceptability. This has the great merit of objectivity, and is a well-tried engineering practice. The Civil Aviation Authority was the first to adopt this approach with what is now known as the ‘1% rule’. Aircraft engineers have always recognized that a disaster may occur as a result of component failure, and have recommended design and safety features so that the risk of failure is ‘extremely improbable’ (1/109 flying hours). If a number of assumptions are made this approximates to a risk of an incapacitating event in a pilot of 1% per year, which happens to be the average annual risk of a heart attack in men aged 45 to 64 years. A pilot with a medical condition may therefore be regarded as a component of aircraft safety and hold a licence if his risk of a cardiovascular event is comparable, i.e. his risk is no greater than his peers or other parts of the aircraft.

There are a number of difficulties in applying the approach described above to other situations and other industries. First, who decides an acceptable level? Second, the epidemiological data generally describe events such as death or heart attack, which may not be the relevant parameter. A heart attack, for example, is a rare cause of road traffic accident; more commonly the driver is found in his vehicle on the verge, ‘slumped over the wheel with the engine still running’. Death may have been sudden in epidemiological terms, but it was not instantaneous; the victim had sufficient warning to pull over to the side of the road. Third, some incapacitating events, neurocardiogenic syncope for example, are clearly relevant to many safety-critical jobs, and yet there are scant data on which to base an objective decision. Fourth, cardiovascular event rates have fallen since the 1% rule was formulated. Nevertheless, the approach is to be commended, and objectivity may be further improved by the use of quantifiable investigations such as exercise testing and echocardiography.

Exercise testing

The data on exercise testing in coronary heart disease are the best established for evaluating the risk of incapacity in employees in safety-critical jobs, e.g. vocational driving. The guidelines relating to vocational drivers were developed in the United Kingdom and adapted by a Task Force of the European Society of Cardiology. They are now being applied more widely to other groups of workers whose occupation may involve an element of risk to themselves or others should that individual suffer cardiovascular collapse.

The protocol for which most information is available is that described by Bruce. He and Fisher examined strategies for risk evaluation of sudden cardiac incapacitation in men in occupations affecting public safety: 2373 men with clinically manifest coronary artery disease who had undergone exercise evaluation were followed up for a mean of 61 months; 300 sudden cardiac incapacitations (cardiac arrest or sudden cardiac death) occurred. Exercise testing in all age groups defined low- and high-risk populations with annual incapacitation rates of 1 and 3%, respectively. The former were those who could reach stage 3 of the Bruce protocol with no chest pain, attain 85% of age-predicted maximal heart rate, and manifest less than 1 mm of ischaemic ST segment depression. A similar message came from the study of 4083 medically treated patients in the Coronary Artery Surgical Study registry. The 32% of patients who could exercise into stage 3 of the Bruce protocol with less than 1 mm ST segment depression on ECG (10 METS) had an annual mortality of 1% or less. By contrast, the annual mortality rate of the 730 patients with 2 mm or greater ST depression was 3.6%, ranging from 5.6% for those patients achieving stage 1 or less of exercise to 2.0% for those patients achieving stage 3. The study also confirmed the overriding prognostic importance of left ventricular function and the poor survival of patients with heart failure. An ability to exceed stage 3 of the Bruce protocol with less than 2 mm of ST segment depression is the best criterion for identifying a population with an annual risk of death of less than 2%.

Driving

Since decisions concerning fitness to drive should be objective and evidence-based whenever possible, a similar approach to that described for pilots is being adopted. An attempt is also being made to be consistent, so that all forms of illness that might cause sudden incapacity should be considered in comparable manner. One condition for which good data are available is epilepsy. Currently the agreed annual acceptable risk of a seizure in the United Kingdom is 2% for vocational drivers and 20% for ordinary drivers, and a driver’s licence entitlement can be determined by reference to well-validated tables of risk, e.g. following a head injury.

The risk of incapacity in drivers with cardiovascular disorders is less easy to quantify; incapacitating syncope occurs in elderly drivers with no structural cardiovascular disorder, whilst others who are apparently at high risk of a cardiac arrest remain asymptomatic for years. However, some drivers with heart disease can be identified as being at an increased risk of an incapacitating event, and attempts are being made in the transport industry and elsewhere to provide objective criteria, which will be applicable across a range of disease processes. Detailed advice is available from http://www.dvla.gov.uk in the section entitled ‘Medical rules, at a glance guide’.

The 2% rule may prove to be the correct criterion for vocational drivers and other workers in similar occupations who suffer from cardiovascular disorders. Society already accepts drivers with vocational licences up to the age of 80 years, by which time their annual risk of a cardiovascular event is 4%. If the assumption is made that half of the events are incapacitating then the acceptable risk accords with the epilepsy criteria, so those drivers whose annual risk of a cardiovascular event is 4% (or death 2%) or greater should not be entitled to hold a vocational licence.

For ordinary drivers a 20% annual risk also seems reasonable for cardiovascular disorders; such a level of risk is in accord with existing guidelines, e.g. shortly after a heart attack. Ordinary driving may be resumed 1 month after a cardiac event provided that the driver does not suffer from angina that may be provoked at the wheel. Vocational driving may be permitted at 6 weeks, subject to a satisfactory outcome from noninvasive testing. In the United Kingdom, ordinary driving licence holders do not need to notify the Driver and Vehicle Licensing Agency (DVLA) if they have made a good recovery and have no continuing disability, but vocational drivers must notify the DVLA. Insurance companies vary in their requirements, but most policies are temporarily invalidated by illness.

Special circumstances

Stress

In the 1950s Friedman and his colleagues developed the idea that chronic psychological stress had a role in the aetiology of coronary heart disease. They described the ‘type A personality’ who had hectic work patterns marked by long hours and organizational chaos, competitiveness, time urgency, and aggression; such individuals seemed particularly prone to heart attacks and sudden cardiac death. Subsequent studies in Europe had difficulty in identifying the type A personality, but better definition of personality traits, such as concealed hostility and failure to cope have been incorporated into questionnaires that have permitted the conclusion that chronic psychological stress is a risk factor for the development of coronary heart disease. Scientific respectability for the role of chronic stress as a risk factor for the development of myocardial infarction came with the publication of the INTERHEART study, which assessed psychological stress from four simple questions about stress at work and at home, financial stress, and major life events in the preceding year, with additional questions assessing the perceived ability to control life circumstances and the presence of depression.

The idea that an acutely stressful incident may trigger a heart attack is also well embedded in Western culture. This has always enjoyed biological plausibility and has more recently acquired scientific credibility. John Hunter was the first to observe that stress could cause angina when he said that he “was at the mercy of any rogue who cares to anger me”. Some increase in the incidence of myocardial infarction or sudden cardiac death has long been recognized after environmental disturbances such as a major earthquake or military assault. However, to argue that such events are triggers is more difficult because the background level of myocardial infarction or sudden cardiac death in any developed community is very high. There are approximately 10 deaths an hour from coronary heart disease in the United Kingdom. Acute physical and psychological distress is likewise very common. Patients and their relatives can almost invariably point to a stressful incident prior to a heart attack and may forget that life is a series of stressful incidents, that heart attacks are extremely common, and coincidences are inevitable, but studies using the epidemiological case crossover control method have identified some events as occurring so much more frequently before a heart attack or sudden cardiac death that they can be recognized as a trigger. The best evidence relates to sudden unaccustomed vigorous effort shortly before (within 2 h of) the attack, especially in emotionally distressed individuals. Anger or acute psychological distress by itself may be a trigger, but this is more difficult to substantiate because of the problem of quantifying psychological stress. The preceding event obviously needs to be sufficiently disturbing to promote the release of catecholamines and provoke the ‘fight or flight’ reaction with an acceleration of heart rate, surge in systolic blood pressure, and increase in ventricular irritability.

The relationship between stress and coronary heart disease has assumed importance for two reasons. First, there may be therapeutic implications: counselling to reduce stress levels before or after a heart attack is commercially available, but there are no outcome data. Second, there has been a huge tide of litigation, generally initiated by bereaved relatives who have been encouraged by solicitors to pursue a claim on the grounds that an action triggered a heart attack. Hitherto a Court of Law has required very persuasive evidence of a causal relationship for a case to succeed: ‘shopkeeper dies chasing thieves’ would be such an example; chronic stress has not yet been accepted as a reason for a settlement.

Travel

Following a cardiac event such as myocardial infarction, individuals should convalesce at home and not travel far for 4 to 6 weeks. Those with no evidence of continuing myocardial ischaemia or heart failure can then travel freely within their own country for pleasure, e.g. a holiday. Business and overseas travel is more problematic because the physical and psychological demands are greater. Additional difficulties for the overseas traveller include the uncertain provision of coronary care facilities in some countries and the justifiable reluctance of insurance companies to provide health cover. Such travel is best deferred until 3 months have elapsed and any necessary further investigations and treatment have been carried out to ensure cardiovascular fitness.

Overseas travel for those with continuing cardiovascular unfitness need not be ruled out. Utilizing the airport services for disabled travellers can ease a passenger through the irritations of customs and passport control at major airports. Modern aircraft can be very comfortable. The cabins are kept at a pressure equivalent to 2000 m so that those with angina are not likely to experience an attack. Businessmen with continuing cardiac disorders may therefore fly to Europe, North America, and other countries with good coronary care services with very little risk. But flights in unpressurized aircraft, work in undeveloped countries or in remote areas of the world, and work in a hostile environment (both climatic and political) are best avoided.

Aircrew are subject to guidelines drawn up by the Joint Aviation Authorities. In the United Kingdom the regulatory agency is the Civil Aviation Authority, whose advice should always be sought.

Cardiac deaths are uncommon in trekkers or workers at high altitude (2440–4570 m). The increase in cardiac output at altitude will exacerbate symptoms in those who already experience symptoms at sea level, but asymptomatic individuals with coronary heart disease are unlikely to be at special risk.

Particular occupations

Exposure to toxic substances

Work involving exposure to certain hazardous substances may aggravate pre-existing coronary heart disease and careful consideration should be given to patients who are returning to jobs involving exposure to chemical vapours and fumes. Methylene chloride, a main ingredient of many commonly used paint removers, is rapidly metabolized to carbon monoxide in the body, and in poorly ventilated work areas blood levels of carboxyhaemoglobin can become elevated enough to precipitate angina or even myocardial infarction. A blood carboxyhaemoglobin level of 2 to 4% has been shown to be associated with impairment of cardiovascular function in patients with angina pectoris. The World Health Organization 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 specific exposure to carbon monoxide, such as car park attendants and furnace workers. 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-h working day: equivalent to exposure to the current occupational exposure standard (50 ppm) for no more than 30 min. Occupational exposure to carbon disulphide in the viscose rayon manufacturing industry is a recognized causal factor of coronary heart disease, but the mechanism remains unclear.

Reports of sudden death from angina are well recognized in dynamite workers, particularly after a period of 36 to 72 h away from work and following re-exposure, an effect almost certainly related to direct action of nitroglycerine on the blood vessels of the heart or peripheral circulation. Individuals with clinical evidence of coronary heart disease should avoid occupational exposure to these substances.

Solvents such as trichloroethylene or 1,1,1-trichloroethane may cause sudden death in workers receiving heavy exposure in poorly ventilated workplaces. The chlorofluorocarbon CFC-113 has been implicated in sudden cardiac deaths and CFC-22 has been reported to cause arrhythmias. Some industrial workers will need proper assessment of their workplace by an occupational physician and occupational hygienist so that they can be advised on their suitability for work handling chlorinated hydrocarbon solvents or involving exposure to gases.

There are no formal medical requirements for workers who have to enter confined spaces where there may be hazards of oxygen deficiency or a build up of toxic gases. Those with heart disease or severe hypertension may need to be excluded. Certain occupations may require the use of special breathing apparatus either routinely (e.g. asbestos-removal workers), or in emergencies (e.g. water workers handling chlorine cylinders). The additional cardiorespiratory effort required while wearing a respirator, combined with the general physical exertion that may be required, usually means that people with a previous history of coronary heart disease are excluded from such work.

Seafarers

The Merchant Shipping (Medical Examination) Regulations in the United Kingdom have recently been revised along the lines of DVLA to take into account the nature of the job, and the likelihood of a further coronary event. The previously draconian regulation that any manifestation of ischaemic heart disease rendered the seafarer unfit to return to sea has been rescinded. The current regulations apply to vessels registered in the United Kingdom above a certain size (a small coaster upwards). They do not necessarily apply to vessels registered in other countries. For more detail see http://www.mcga.gov.uk.

Working in hot conditions

Working in hot conditions may prove hazardous for some patients with heart disease. High ambient temperatures or significant heat radiation from hot surfaces or liquid metal, added to the physical strain of heavy work, will produce vasodilatation of muscle and skin vessels. Compensatory vascular and cardiac reactions to maintain central blood pressure may be inadequate and lead to reduced cerebral or coronary artery blood flow. The possibility of syncope will be enhanced by the use of drugs with vasodilating and negative inotropic actions; some reduction in dosage may be necessary.

Working in cold conditions

Cold exacerbates myocardial ischaemia. Individuals with coronary heart disease should therefore exercise caution. Impaired circulation to the limbs will result in an increased likelihood of claudication, risk of damage to skin (frostbite), and poor recovery from accidental injury to skin and deeper structures.

Implanted devices

Cardiac pacemakers are generally implanted into older patients who have idiopathic degeneration of their conduction system. However, both heart block and sinoatrial disorder are well-recognized complications of coronary heart disease. Single- and dual-chamber (invariably VVI or DDD) pacemakers are rarely vulnerable to electromagnetic interference and no modification of lifestyle is necessary, although patients should know that their device can trigger alarms at airports and elsewhere.

The implantable cardioverter–defibrillator (ICD) has the capacity to detect and treat ventricular tachycardia and fibrillation, either by antitachycardia pacing or by a shock, in patients in whom a further cardiac arrest is anticipated. Both the shock and the arrhythmia are potentially incapacitating. In North America and Europe, patients with ICDs have restrictions placed upon them, e.g. with regard to driving. They commonly have severe underlying heart disease and may well not be able to work, but if they can do so, then this should be in an environment that is free from electromagnetic interference. There has been one report of ICD malfunction in the vicinity of an electronic antitheft surveillance system. The development of cardiac resynchronization therapy (CRT) using a biventricular pacemaker has proved very helpful in the treatment of some patients with heart failure. CRT and ICD capability is commonly combined in a single device.

There has been considerable interest in the possibility that mobile telephones might interfere with pacemakers and ICDs. Studies have shown that this is a theoretical possibility and that reprogramming of a pacemaker can be achieved under exceptional circumstances if the telephone is held close (<20 cm) to the pacemaker. In practice no clinically significant interference has yet been reported, but individuals are advised to use the hand and ear furthest from the pacemaker and not to ‘dial’ with the telephone near to the pacemaker.

Retirement and end of life

Despite modern treatments some patients will experience multiple coronary events that eventually lead to extensive ventricular damage and persisting symptoms of fatigue and dyspnoea, with signs of heart failure. Such individuals should be warned of their limited prognosis. Some should be advised to retire, which is never an easy decision.

There is commonly a discrepancy between an individual’s symptoms and the objective cardiac data. For some patients a heart attack proves devastating: the man who has always enjoyed robust good health may appear to be very symptomatic despite good ventricular function and no evidence of continuing myocardial ischaemia. One explanation for this is the profound psychological disturbance that sometimes follows the development of cardiovascular disease. At the other extreme some patients seem well and active despite appalling ventricular function, although puzzlingly for the lay observer they are prone to experience sudden cardiac death despite apparently being ‘so well’. As always, common sense has to override the results of investigations, and individuals can defy the predictions made on the basis of good epidemiological outcome data.

Patients (with their partners if appropriate) should be given the opportunity of a frank discussion about their prognosis, but some would rather not know and that attitude should be respected. However, most need to put their affairs in order, and what to say exactly is one of the most difficult problems in cardiology. The victim’s quality of life may be excellent. There is no point in advising a restricted lifestyle or retirement. The only definite lifestyle trigger of a heart attack, namely sudden unexpected vigorous exercise, should be avoided. Otherwise, normal activities should continue, with the knowledge that the chance of successful resuscitation following a coronary event are greater in developed countries, in fact better in most of Europe and North America than in the United Kingdom.

Early retirement on grounds of ill health following a coronary event is sometimes seen as an attractive option. However, most permanent sickness policies contain a clause which states that benefit will only be payable if the subscriber is ‘totally unable to follow his former occupation’, which is often not the case after a heart attack or coronary artery bypass grafting. Advice about retirement should only be given after due consideration and a review of the job terms and conditions.

Further reading

Joy MD (ed.) (1999). Second European Workshop in Aviation Cardiology. Eur Heart J, Suppl D.Find this resource:

Petch MC (1998). Task Force Report: driving and heart disease. Eur Heart J, 19, 1165–77.Find this resource:

Price A, Petch MC (2007). Cardiovascular disorders. In: Palmer K, Cox RAF, Brown I (eds) Fitness for work, 4th edition. Oxford University Press, Oxford.Find this resource:

Rosengren A, et al. (2005). Association of psychological risk factors with risk of acute myocardial infarction in 11 119 cases and 13 648 controls from 52 countries (the INTERHEART study): case-control study. Lancet, 364, 953–62.Find this resource:

Stansfield SA, Marmot MG (2002). Stress and the heart. BMJ Books, London.Find this resource: