2 Clinical need and practice

2 Clinical need and practice

2.1 Coronary artery disease (CAD) is the commonest cause of death in England and Wales. It is characterised by the development of lipid-laden coronary arterial plaques, which reduce the blood supply to the heart muscle. Significant CAD is defined as a stenosis (narrowing) of more than 70% of the diameter of at least one major epicardial artery segment or more than 50% of the diameter of the left main coronary artery.

2.2 Angina (chest pain) is the most common symptom of CAD. It is usually provoked by exercise and relieved by rest. Angina of rapidly increasing frequency, or experienced at rest, is called unstable angina. CAD can also lead to heart attack (myocardial infarction, MI) and sudden cardiac death. MI is characterised by severe chest pain persisting for at least 20 minutes, a rise in cardiac enzymes in the serum, and/or an abnormal electrocardiogram (ECG).

2.3 About 2.65 million people in the UK have CAD, and of these 1.2 million have had an MI. There were an estimated 275,000 heart attacks in the UK in 2001, and 335,000 new cases of angina are diagnosed each year. CAD is more prevalent in men than in women. The prevalence of CAD increases with age, and varies across geographic regions and socioeconomic groups.

2.4 Preventative strategies for reducing the frequency of CAD include smoking cessation, diet modification, exercise, and treating conditions that exacerbate progression of the disease, such as hyperlipidaemia, hyperglycaemia, hypertension and blood hypercoagulability. Medical treatment of angina symptoms includes the use of nitrates, beta-adrenergic blockers and/or calcium channel blockers. In severe CAD, revascularisation may be required, using surgical procedures such as coronary artery bypass grafting (CABG) or via the use of percutaneous coronary intervention (PCI), commonly with the insertion of an intraluminal coronary stent.

2.5 The cost of CAD to the UK healthcare system in 1999 was estimated in the Assessment Report (see Appendix B) at £1.7 billion; the total annual cost was around £7 billion when informal care and productivity losses were included. More than 378,000 inpatients were treated for CAD in NHS hospitals in 2000/2001. Approximately 28,500 CABG and 39,000 PCI procedures are performed each year in the UK.

2.6 The individual likelihood for CAD can be estimated from age, gender, ethnic group, family history, existence of symptoms, associated comorbidities and the results of tests such as resting electrocardiography (rECG). rECG is a commonly used test because it is readily available in primary care and is inexpensive, but because it does not exclude CAD, it is of limited diagnostic value. Stress ECG (sECG) and coronary angiography (CA) are commonly used in clinical practice for the diagnosis of CAD.

2.7 sECG is normally recorded during progressive exercise on a treadmill, and so is not suitable for people for whom treadmill exercise is difficult or impossible.

2.8 CA involves manipulating a cardiac catheter into the heart from a vein or artery in a limb. A contrast medium is injected through the catheter, and its progress monitored by a rapid series of X-rays. CA provides mainly anatomical information and is used to measure the degree of stenosis. It is considered the 'gold standard' for defining the site and severity of coronary artery lesions. However, CA findings are not always a reliable indicator of the functional significance of a coronary stenosis. Routine use of CA without prior non-invasive testing is not advisable, because of its high cost and associated mortality and morbidity. Potential complications include non-fatal MI (0.1%), stroke (0.1%) and death (0.1–0.2%).

2.9 Other frequently used non-invasive techniques include myocardial perfusion scintigraphy (MPS) and echocardiography. Imaging techniques such as magnetic resonance imaging and positron emission tomography are used less frequently.