EXERCISE TESTING

Exercise testing, if practicable, is important both to provide objective confirmation of exercise induced ischaemia and as an independent indicator of prognosis [A].23 ,24 It will usually take the form of treadmill exercise according to a standard protocol with ECG monitoring. The Bruce protocol is the one most commonly used in the UK.25 An exercise ECG is conventionally said to be positive if it shows 1 mm or more of reversible plane ST segment depression. Also important are whether or not the exercise induces typical symptoms, the amount of exercise the patient can achieve, the presence of a normal or abnormal blood pressure response to exercise, and the appearance of the patient while exercising.26 ,27 Exercise electrocardiography cannot be regarded in isolation as an effective screening test for ischaemic heart disease. Patients with non-obstructive coronary artery disease or a well developed collateral circulation may have negative exercise tests; on the other hand exercise testing of a population with a low prevalence of ischaemic heart disease will produce a high proportion of false positive tests.28 False positive exercise recordings are also more common in women. The working group emphasised the importance of exercise testing in the evaluation of patients with suspected angina, but were convinced that it should be preceded by careful clinical evaluation, and the result interpreted by trained clinicians. In patients with a clinical diagnosis of angina it is not necessary to wait for exercise testing to be carried out before instituting antianginal treatment [A].29 Similarly, antianginal treatment should not be withdrawn when carrying out exercise testing unless this is specified for particular purposes—for example, the issue of a public service vehicle licence [B].

MYOCARDIAL PERFUSION SCANNING

Myocardial perfusion scanning involves the injection, at peak exercise or during stress induced using adenosine, dipyridamole, or dobutamine, of a radionuclide which is taken up by the myocardium. The creation of a myocardial perfusion image depends upon the ability of a radiopharmaceutical to be distributed throughout the myocardium in proportion to regional blood flow. Typically, two sets of images are acquired using a gamma camera, one reflecting perfusion at peak stress and the other at resting perfusion. Radiopharmaceuticals distribute uniformly in normally perfused myocardium. In areas supplied by coronary arteries with functionally significant stenoses there is a stress defect that improves on rest imaging (reversible defect). Stress defects that fail to improve on rest imaging (fixed defects) generally represent infarcted areas.

Myocardial perfusion imaging has a higher diagnostic sensitivity and specificity for coronary artery disease than exercise electrocardiography (80% and 92% v68% and 84%, respectively).30 Comparisons using receiver operating characteristic curves have also confirmed the superior diagnostic capabilities of perfusion imaging.31 The requirements for expensive equipment and appropriately trained staff, together with the radiation burden to the patient, mean that perfusion imaging is usually employed for diagnosis when exercise electrocardiography is unhelpful or leaves doubt. This may occur when the resting ECG is abnormal, equivocal ST segment changes occur with exercise, exercise electrocardiography is normal despite a high pretest probability of disease, abnormal ST segments are seen despite a low pretest probability of disease, or only submaximal exercise has been achieved [B].

There is evidence that myocardial perfusion imaging provides prognostic information which is more reliable than either exercise electrocardiography or coronary angiography.32 ,33 A normal stress perfusion study predicts a favourable prognosis for cardiac event rate (less than 1% per year), even in patients with known coronary disease.34-36 Conversely severe and extensive reversible ischaemia predicts an adverse prognosis.37

STRESS ECHOCARDIOGRAPHY

Stress echocardiography involves the imaging of areas of altered myocardial contractility under conditions of exercise or pharmacological stress. As with myocardial perfusion scanning, the object is to improve the sensitivity and specificity of conventional exercise electrocardiography. Stress echocardiography and myocardial perfusion imaging probably provide comparable results in the diagnosis of coronary disease but perfusion imaging may provide more reliable information about prognosis.38 ,39

CORONARY ANGIOGRAPHY

Coronary angiography gives a uniquely detailed anatomical record of the coronary arteries and their stenoses. Strictly speaking, it does not diagnose either coronary atheroma (since vessel wall disease may be present when the lumen is normal) or myocardial ischaemia (since it does not give full information about coronary flow). It provides information valuable in risk stratification and it is an essential prelude to interventions such as angioplasty or coronary artery bypass grafting.

Coronary angiography is an invasive investigation involving arterial puncture and the introduction of catheters which are passed through the aorta to the mouths of the coronary arteries. It is usually performed on a day case basis. The overall mortality associated with the procedure is of the order of 1 in 2000 and the serious complication rate is about 1%.40

In many countries coronary angiography is regarded as a routine investigation in patients with clinical features of angina.4 In the UK, access to coronary angiography is limited for many patients by lack of resources or by purchasing restrictions. Several attempts have been made to evaluate the “appropriateness” of referral for coronary angiography, based on criteria such as symptom severity, exercise test performance, and adequacy of medical treatment.41-44 These criteria can be used to form the basis of a scale of priority for investigation; however, for prospective planning as opposed to retrospective audit, a numerical scale, where the decision point can be adjusted in response to available resources, is more likely to be helpful than a simple division into “appropriate” and “not appropriate”.

Numerous attempts have also been made to define “appropriate” numbers of investigations for a given size of population.45 ,46 These have inevitably been based on consensus rather than on objective evidence, and are further complicated by the marked variations in rates of investigation between different districts in the same geographical area.47 Where rationing of resources is inevitable, it should be based on clear, explicit, and objective clinical criteria.

CONTROL OF RISK FACTORS

There is now excellent evidence that control of risk factors in patients with angina leads to an improved outcome both in terms of a reduced incidence of ischaemic events and of improved survival. Recommendations include:

• Advice on stopping smoking [A]

• Adequate control of blood pressure following British Hypertension Society guidelines54 [A]

• Lowering of plasma cholesterol by either dietary or pharmacological means55 ,56 [A]

• Regular exercise, control of diabetes, and weight reduction towards an ideal body mass index [C]

• Prescription of low dose aspirin unless contraindicated or not tolerated57 ,58 [A]

 Detailed dietary advice is beyond the scope of this paper. There is some clinical trial evidence to support the use of antioxidant vitamins and this is currently being evaluated in a large randomised trial.59

It is recognised that the evidence for a beneficial effect of aspirin is less strong when consideration of trials is restricted solely to those performed in patients with stable angina, but the working group saw no good reason for considering these in isolation from other groups of patients with atheromatous vascular disease. Further justification and references to support these recommendations are given elsewhere.3 ,4

MEDICAL CONTROL OF SYMPTOMS

This can be divided into immediate symptom control and background antianginal medication. Sublingual glyceryl trinitrate remains the standard treatment for immediate symptom control [B]. Classes of agents available for background antianginal medication are listed in table 1. For each of the agents listed there is clinical trial evidence for efficacy in symptom control versus placebo.60-69There is no direct evidence that any of the agents listed has a significant effect on the incidence of sudden death or myocardial infarction when prescribed for the treatment of angina. This reflects the absence of clinical trials with sufficient power to evaluate these outcomes. β Blockers have been shown to reduce mortality when prescribed to patients before or following myocardial infarction.70 ,71 Verapamil has been shown to reduce the number of new cardiovascular events following myocardial infarction in a subgroup of patients without heart failure.72 Although there have been numerous comparisons between different classes of antianginal agents in terms of symptom reduction, these have almost always involved fixed dose comparisons; there is little evidence for the intrinsic superiority of one class over another in terms of symptom relief. It is clear, however, that individual patients differ markedly in their experience of side effects, and in practice the choice of a particular agent will often be determined by patient acceptability. Similarly, differences between agents within a given class tend to reflect differences in dose schedule and side effects rather than efficacy—a detailed description is beyond the scope of the present paper.

It is a commonly held belief that a combination of two antianginal agents makes for enhanced antianginal efficacy while minimising side effects. There is some support for this from clinical trials,69 ,70 but combination treatment has seldom been compared with an optimised dose of either agent alone, and it is sensible to evaluate the effect of an adequate dose of a single agent before moving on to another single agent or to combination therapy [C]. As a general rule background antianginal agents should be tailed off rather than discontinued abruptly, unless they are causing serious side effects. There is very little evidence that the use of three or more antianginal agents provides any additional advantage.

• Use sublingual nitrate for immediate symptom control [A]

• Background antianginal medication will improve symptoms [A]

• β Blockers may reduce incidence of cardiac events and improve survival [B]

• Evaluate the effect of an adequate dose of a single agent before moving on to another single agent or to combination treatment [C]

REVASCULARISATION

Coronary revascularisation is nearly always done to relieve symptoms, and in some cases to improve survival. There is clinical trial evidence that surgical revascularisation by coronary bypass grafting gives a better long term survival than medical management in patients with left main coronary stenosis, three vessel coronary disease, or two vessel disease where one of the vessels was in the proximal left anterior descending artery. Benefit was greater in patients with impaired left ventricular function despite the greater perioperative mortality.51 ,73 ,74 There is currently no evidence that coronary angioplasty in the context of stable angina improves survival, but in randomised trials it has been shown to give better symptomatic relief than medical treatment.75 ,76The vast majority of coronary angioplasty procedures are done in patients with single or two vessel disease who would be expected to have an excellent short to medium term survival. In these patients angioplasty and bypass grafting give similar relief of symptoms for the same low mortality rates, although angioplasty patients are more likely to remain on some antianginal medication and more likely to require a second procedure.77 ,78 In patients with multivessel disease the outcome of angioplasty and bypass grafting is similar in terms of early symptom and operative mortality, but more angioplasty patients require a second procedure and they are more likely to have recurrent angina within five years.79 Coronary stenting is an integral part of modern angioplasty practice. There is a consensus that it has reduced the immediate complication rate and reduced the rate of restenosis, though direct clinical trial evidence is lacking.75 ,76 Randomised trials of elective stenting have tended to show lower angina recurrence and second procedure rates at the price of more vascular complications.80 ,81 The latter are particularly associated with intensive anticoagulant regimens that have now been superseded.82

The overall average mortality for elective coronary bypass grafting or coronary angioplasty in stable angina is around 1%. The 1997 UK mortality rate for all patients having coronary bypass grafting was 3%, but this includes unstable angina and emergencies. In cost benefit analyses the need for repeat procedures reduces the cost advantage of coronary angioplasty over bypass grafting until this becomes insignificant at about five years.83 It is important to note that the patients entered into these trials were those in whom both angiooplasty and bypass grafting were technically feasible, and that neither stenting nor statins were available when the trial began. Angiooplasty is not usually suitable for patients with unprotected left main stenosis, diffuse three vessel disease, or for some patients with chronically occluded coronary arteries.

Coronary revascularisation rates, whether by angioplasty or bypass grafting, have increased much more slowly in the UK than in several other countries. As for coronary angiography, this reflects both limited resources and limited purchasing. On the one hand, there is little doubt that patient and doctor preference is increasingly towards an interventionist approach; on the other, rationing of limited resources in the context of a free National Health Service is legitimate, particularly where the procedure is being performed to improve quality of life rather than to prolong survival.84As for coronary angiography there are major differences between health districts in revascularisation rates which are hard to explain rationally.52 In many centres an imbalance between rate of referral and refunded throughput has led to the accumulation of long waiting lists for coronary bypass surgery. The situation has been further complicated by the Patients’ Charter requirements for all patients to receive treatment within one year. Several attempts have been made to devise scoring systems to determine whether patients should be offered surgical revascularisation; if this approach is adopted it is important that the criteria should be explicit, objective, and shared with patients and purchasers alike.85 As an absolute minimum patients with severe symptoms in whom bypass grafting can objectively be shown to improve survival should be able to have surgery without delay.

REHABILITATION

Full restoration of patients to satisfactory social function and work may require more than relief of symptoms and correction of risk factors. Modern concepts of rehabilitation emphasise the importance of early explanation, full involvement of the patient and his or her family in the rehabilitation process, attention to psychological aspects of the diagnosis, and long term reinforcement of life style changes. These are discussed in more detail in the British Cardiac Society guidelines on cardiac rehabilitation.86

PRIMARY CARE

General practitioners are the points of presentation for most patients with chest pain. General practice assessment should include:

• Clinical assessment of symptoms, in the light of knowledge of the patient, his family and environment

• Clinical examination to identify other possible causes of chest pain and other causes of angina (for example, anaemia, valve disease)

• Assessment of coronary risk factors (family history, smoking, diabetes, hypertension).

 Further investigation at the general practitioner level should include a baseline 12 lead ECG and cholesterol/HDL cholesterol measurement.

Management at the general practice level focuses on advice/explanation, risk factor reduction (especially smoking), and medical treatment which would normally include low dose aspirin, sublingual glyceryl trinitrate, one or more background antianginal agents as discussed above, and, where appropriate, a lipid lowering agent.

The working party recommends that all newly diagnosed cases of angina should be referred for an objective assessment of myocardial ischaemia by one of the methods described above, unless contraindicated by intercurrent illness, other disability, or patient preference. Such referral would usually be to a physician with special interest and training in cardiology. Open access referral for stress testing may be appropriate, provided there is an adequate mechanism for expert review and consultation if necessary. It is not intended that the physician to whom such referral is made should take over continuing care of the patient unless this is specifically requested. Referral is also indicated where the diagnosis is in doubt or where a positive diagnosis would have major implications for the patient’s livelihood.

Referral for treatment is indicated for patients of any age with severe, unstable or rapidly progressive symptoms, for patients with secondary angina from a remediable cause, or for patients with unacceptable symptoms despite adequate medical treatment.

SECONDARY CARE

Secondary care may be provided by a physician with special interest and training in cardiology, or by a specialist cardiology unit acting in a secondary care role.

Facilities available at a secondary care referral centre should include:

• Advice available from a consultant or other specialist

• Exercise electrocardiography to confirm the diagnosis and for risk stratification

• Other non-invasive techniques, including myocardial perfusion imaging, as discussed above

• Access to a wider range of facilities for risk assessment and modification such as a lipid clinic

• Cardiac care unit with dedicated beds and monitoring facilities.

 Management at secondary care level is essentially an extension of that at primary care level and should be a collaborative venture with the primary care team.

Referral from secondary to specialist cardiac care is indicated when intervention by angioplasty or bypass surgery is felt to be necessary on the basis of symptom severity or the severity of ischaemia as assessed by non-invasive testing. Referral may also be indicated when the diagnosis is in doubt, particularly in patients with recurrent hospital admissions for atypical symptoms. Where secondary care is provided by a number of physicians, only one of whom has specialist training in cardiology, it is desirable that referrals to a specialist cardiac centre should be channelled through the specialist physician. A close working relationship between secondary and specialist cardiac care is essential.

SPECIALIST CARDIAC CARE

In addition to providing expert advice, one of the major functions of specialist cardiac referral centres is to perform invasive investigations with a view to possible cardiac intervention. The principal resources required for this are a catheter laboratory suite, cardiac surgery operating facilities, an intensive care unit, and associated inpatient beds. The extent to which investigative and interventional facilities can be separated has been debated; the risk of diagnostic angiography is small but it is accepted that angioplasty needs effective surgical back up. In practice specialist cardiac centres need to duplicate many of the non-invasive facilities of secondary care centres, and many units function as combined secondary and specialist care centres.

Specialist cardiac centres needs to be organised so as to respond rapidly to emergencies; at the same time they must be efficient in dealing with routine cases. They need to set high educational and audit standards.

GENERAL PRACTICE

  SECONDARY CARE CENTRES

SPECIALIST CARDIAC CENTRES