Cardiology

Acute coronary syndromes (ACSs) occur when CHD is associated with the sudden rupture of plaque inside the coronary artery and can consist of unstable angina, non-ST-segment elevation MI (NSTEMI), and ST-segment elevation MI (STEMI).

CHD can present with silent ischaemia (especially in diabetes mellitus). However, CHD usually presents as chest pain due to an ACS, but it may also present with symptoms resulting from arrhythmia or heart failure, or be detected incidentally by ECG.

Heart failure is a frequent complication of MI and increases the mortality risk by up to fourfold. Approximately 40% of MIs are associated with left ventricular systolic dysfunction. ECGs, echocardiograms, and serum natriuretic peptide levels can be used to assess heart failure and can contribute to diagnosis, monitoring, and prognosis.

1.      Nature of original cardiovascular event - persistence of chest pain during exercise, the risk of arrhythmia, and the level of left ventricular function. Additionally, the possibility of silent ischaemia needs consideration for high-risk individuals. While angioplasty ensures a speedier return to work than CABG, long-term employment prospects are similar in both treatment groups

2.      Recurrent cardiac events – any arrhythmias, recurrent hospitalisations?

3.      Residual Loss of function following cardiac event - individual’s functional capacity should be assessed prior to return to work. For cardiac disease, an exercise stress test will give the required information, while those with cardiac failure may need further investigation. Cardiac failure formerly meant that a return to work was unlikely, but improvements in treatment of the underlying cause mean now that more people with heart failure can return to work. Using the NYHA criteria for heart failure, individuals with functional capacity I and II are likely to return to their previous role. Those with NYHA functional capacity III and IV or those returning to a very strenuous job may require additional functional testing and cardiological opinion

4.      Comorbid conditions – depression, migraine, chronic bronchitis, smoking, BMI, cholesterol, hypertension,

It is estimated that up to 80% of patients with uncomplicated MI will return to work. When work is resumed, the levels and duration of activity should be increased progressively. In general, physical activity is good for the heart but the degree of physical activity must take into account previous fitness and the results of exercise testing. Patients with stable angina can safely work within their limitations of fitness but should not be put in situations where their angina may be readily provoked. Patients with persistent angina or an abnormal exercise test should be assessed for myocardial revascularization. Following an acute coronary event, those with no complications and good exercise tolerance may return to work in 4–6 weeks

Fatigue usually resolves over time. It may be helpful to arrange reduced hours or other temporary restrictions, but these should be defined and not left open-ended. A recent systematic review investigating older workers with cardiac disease has suggested that multicomponent interventions could be of benefit for those returning to work.18 This could include a structured return to work plan, job-simulated cardiac rehabilitation and education

As a general rule, activities that cause no symptoms can be undertaken safely. Careful history taking will identify what activities are possible, initially by eliciting activities of daily living then matching these with equivalent work activities. stage 1 of the Bruce protocol approximates to 4.6 METs, stage 2 is 7.0 METs, stage 3 is 10.1 METs, and stage 4 is 12.9 METs. Jobs that may require extreme physical effort, for example, those in the emergency services, may be unsuitable for workers with CHD

4-5 METs – painting, light carpentry

5-6 METs – digging

7-8 METs – sawing hardwood

Individuals who are asymptomatic and can achieve a good workload without adverse features have a very low risk of further cardiac events. This applies particularly to younger individuals and employers should little hesitation in taking them back to work.

An individual who reaches stage 4 of the Bruce protocol on a treadmill is at such low risk of further cardiac events that vocational driving may be permitted.

The carefully considered Driver and Vehicle Licensing Agency (DVLA) guidelines are now being applied more widely to other groups of workers whose occupation involves an element of risk to themselves and others in the event of cardiovascular collapse.

Most employees, however, are not required to demonstrate such high levels of cardiovascular fitness. Those whose early investigations are inconclusive will require further tests, often including MRI or radionuclide imaging to assess ventricular function and myocardial perfusion.

Those who have continuing symptoms, or whose non-invasive investigations are unsatisfactory will be recommended to undergo coronary angiography with a view to myocardial revascularization.

studies have found that sudden cardiac death in firefighters less than 45 years of age were primarily due to lifestyle factors such as obesity, smoking, hypertension, and previous history of CHD. Furthermore, fire fighters may be exposed to chemical hazards (carbon monoxide, fine particulate matter, and other cardiac toxins), which may increase the risk of sudden Mis

There is considerable evidence to support the role of job strain (a combination of high work demands and low job control) as a risk factor for CHD. Previous research suggests an average 50% excess cardiovascular risk among employees with work stress17 and job strain causes a 1.8 times higher age-adjusted risk of incident ischaemic heart disease (particularly in younger male populations between 19–55 years of age).

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.

Shift work can also involve working beyond the 40-hour working week and a recent systematic and meta-analysis on overtime and CVD has found a 40% excess risk of CVD in those who work overtime.

 There are no formal medical standards for workers who have to enter confined spaces where there may be hazards of oxygen deficiency or a build-up of toxic gases. However, workers 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, should be factored in to any risk assessment undertaken and may require specialized input from the treating cardiologist to confirm exercise capability appropriate to the demands of the role.

High ambient temperatures or significant heat radiation from hot surfaces or liquid metal, added to the physical strain of heavy work, will produce profound vasodilatation of muscle and skin vessels. Work environments such as bakeries, mines, foundries, compressed air tunnels, and smelting may expose employees to high temperatures. Compensatory vascular and cardiac reactions to maintain central BP may be inadequate and lead to reduced cerebral or coronary artery blood flow.

Cold is a notorious trigger of myocardial ischaemia and caution must therefore be exercised in placing individuals with CHD in cold working environments. Impaired circulation to the limbs will result in an increased risk of claudication, risk of damage to skin (frostbite), and poor recovery from accidental injury to skin and deeper structures. Clear work procedures that include short periods spent in the cold, provision of appropriate cold weather clothing and regular hot drinks, coupled with clear safety guidelines may reduce risk sufficiently to allow the individual to continue working in those conditions

Transient cardiac arrhythmias (e.g. extrasystoles) are common and do not usually indicate heart disease. They may be provoked by alcohol and coffee. Assessment by a specialist is recommended if symptoms persist. A few individuals suffer recurrent arrhythmias. The commonest is AF, which affects 2% of the population and tends to be paroxysmal in individuals of working age. Drug treatment is sometimes required and individuals need to withdraw from work and rest for a short period.

A person is not fit to hold an unconditional licence:

if the person has a history of recurrent or persistent arrhythmia that may result in syncope or incapacitating symptoms

Syncope, other than a simple faint, requires specialist evaluation, which may include neurological as well as cardiovascular review. Following unexplained syncope, provocation testing and investigation for arrhythmia must be undertaken. If no major problem is found, return to work is recommended, including re-licensing for vocational drivers after 3 months (if the trigger can be avoided or it has been established the syncope was vasovagal). If the syncope is unexplained, vocational licences will be revoked for 12 months.27 Careful follow-up is essential. Increasingly, implantable loop recorders are being used to identify the cause for syncope. These small devices are implanted under the skin and continuously record the cardiac rhythm on a loop. They will automatically store evidence of dangerous rhythms, but can also be activated by patients when they have an attack. The devices can be remotely monitored. Strong electromagnetic fields may cause artefactual recordings or potentially delete the stored electrograms but are unlikely to present any significant risk to the patient.

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.

The implantable cardioverter defibrillator (ICD) is now the preferred treatment for individuals with haemodynamically significant ventricular tachycardia and/or fibrillation whose arrhythmia is refractory to drugs or myocardial revascularization; the ICD device often has cardiac resynchronization therapy capacity

In accordance with the new 2022 Austroads Assessing fitness to drive for commercial and private vehicle drivers, Section 2.2.6 implantable cardioverter defibrillators states:

“People fitted with an implantable cardioverter defibrillator (ICD) have a risk of sudden incapacity, which poses a crash risk. The risk is mainly a consequence of the underlying condition; however, there is also a risk of inappropriate discharge of the device (i.e. when there is no ventricular arrhythmia). This risk is considered unacceptable for commercial vehicle drivers to hold an unconditional licence. A conditional commercial licence may be considered by the driver licensing authority on the advice of a specialist in electrophysiology based on the nature of the driving tasks and criteria outlined in the medical standards table when the device is inserted for primary prevention. A person is not fit to hold a conditional commercial licence when the ICD is inserted for secondary prevention.”

Patients with controlled hypertension can expect to manage most work. Occasionally, frequent postural changes prove troublesome, due to altered central and peripheral vascular responses. Very heavy physical work and exposure to very hot conditions with high humidity may result in postural hypotension. Group 2 vehicle driving is allowed provided that the BP is under satisfactory control. However, drivers must not drive if systolic BP is 180 mmHg or greater, or diastolic BP is 100 mmHg or greater.

Lifestyle factors have been indicated in the management of hypertension such as weight reduction, smoking cessation, diet, alcohol, and salt restriction.8 The association of hypertension and stress has also been explored but has not been identified as a lifestyle factor by the European Arterial Hypertension Guidelines

A person is not fit to hold an unconditional licence:

• if the person is subject to angina pectoris.

A conditional licence may be considered by the driver licensing authority subject to annual review, taking into account the nature of the driving task and information provided by the treating specialist as to whether the following criteria are met:

• either or both:

• there is an exercise tolerance ≥ 90% of the age/sex predicted exercise capacity according to the Bruce protocol or equivalent functional exercise test protocol;

• a resting or stress echocardiogram or a myocardial perfusion study, or both, show no evidence of ischaemia; and

• there are minimal symptoms relevant to driving (chest pain, palpitations, breathlessness).

If myocardial ischaemia is demonstrated, a coronary angiogram may be offered.

A conditional licence may be considered, subject to annual review, if the following criterion is met:

• the coronary angiogram (invasive or CT) shows lumen diameter reduction < 70% in a major coronary branch, and < 50% in the left main coronary artery.

A person is not fit to hold an unconditional licence:

• if the person has a history of recurrent or persistent arrhythmia that may result in syncope or incapacitating symptoms.

A conditional licence may be considered by the driver licensing authority subject to annual review, taking into account the nature of the driving task and information provided by the treating specialist as to whether the following criteria are met:

• there is a satisfactory response to treatment; and

• there are minimal symptoms relevant to driving (chest pain, palpitations, breathlessness); and

• appropriate follow-up has been arranged.

The person should not drive for:

• at least 4 weeks following PCI;

• at least 4 weeks following initiation of successful medical treatment;

• at least 3 months following open chest surgery.

A conditional licence may be considered by the driver licensing authority subject to annual review, taking into account the nature of the driving task and information provided by the treating specialist as to whether the following criteria are met:

• it is at least 6 months after the arrest; and

• a reversible cause is identified and recurrence is unlikely; and

there are minimal symptoms relevant to driving (chest pain, palpitations, breathlessness).

A conditional licence may be considered by the driver licensing authority subject to annual review, taking into account the nature of the driving task and information provided by the treating specialist as to whether the following criteria are met:

• it is at least 4 weeks after insertion of the cardiac pacemaker; and

• the relative risks of pacemaker dysfunction have been considered; and

• there are normal haemodynamic responses at a moderate level of exercise; and

there are minimal symptoms relevant to driving (chest pain, palpitations, breathlessness).

The person should not drive for at least 3 months following initiation of treatment.

A person is not fit to hold an unconditional licence:

• if the person has an electrocardiographic abnormality – for example, left bundle branch block, right bundle branch block, pre-excitation, prolonged QT interval or changes suggestive of myocardial ischaemia or previous myocardial infarction.

A conditional licence may be considered by the driver licensing authority subject to annual review, taking into account the nature of the driving task and information provided by the treating specialist as to whether the following criteria are met:

• all of the following:

• the condition has been treated procedurally or medically for at least 3 months; and

• there is a satisfactory response to treatment; and

• there are minimal symptoms relevant to driving (chest pain, palpitations, breathlessness); or

• follow-up investigation has excluded underlying cardiac disease.

A person is not fit to hold an unconditional licence:

• if the person has heart failure.

A conditional licence may be considered by the driver licensing authority subject to annual review, taking into account the nature of the driving task and information provided by the treating specialist as to whether the following criteria are met:

• there is a satisfactory response to treatment; and

• there is an exercise tolerance ≥ 90% of the age/ sex predicted exercise capacity according to the Bruce protocol or equivalent functional exercise test protocol; and

• there is an ejection fraction ≥ 40%; and

• the underlying cause of the heart failure is considered; and

there are minimal symptoms relevant to driving (chest pain, palpitations, breathlessness).

A person is not fit to hold an unconditional licence:

• if the person has blood pressure consistently > 170 systolic or > 100 diastolic (treated or untreated).

A conditional licence may be considered by the driver licensing authority subject to annual review, taking into account the nature of the driving task and information provided by the treating specialist* as to whether the following criteria are met:

• the person is treated with antihypertensive therapy and effective control of hypertension is achieved over a 4-week follow-up period; and

• there are no side effects from the medication that will impair safe driving; and

there is no evidence of damage to target organs relevant to driving

The person can resume driving within 24 hours if the episode was vasovagal in nature with a clear-cut precipitating factor (e.g. venesection) and the situation is unlikely to occur while driving. The driver licensing authority should not be notified.

The person should not drive for at least 3 months after syncope due to other cardiovascular causes.

A person is not fit to hold an unconditional licence:

• if the condition is severe enough to cause episodes of loss of consciousness without warning.

A conditional licence may be considered by the driver licensing authority subject to

annual review, taking into account the nature of the driving task and information provided by the treating specialist as to whether the following criteria are met:

• the underlying cause has been identified; and

• satisfactory treatment has been instituted; and

the person has been symptom-free for 3 months.