Angina pectoris is a common cardiac condition that, without treatment, has a significant morbidity and mortality. It is thought that 20,000-40,000 per million Europeans suffer from angina.
For most people, stable angina is caused by occlusion of a coronary artery or arteries by a stable plaque. In this case, the plaque abuts into the lumen of the coronary artery.
When myocardial oxygen demand increases, the plaque may prevent the adequate flow of blood distally, causing myocardial ischaemia which ultimately presents as angina.
Risk factors include age (over 45 for men and over 55 for women), race (South Asian), obesity, poor diet, smoking, hypertension, hyperlipidaemia, diabetes mellitus, family history and elevated homocysteine levels.
Any condition causing myocardial perfusion may cause angina. Oesophageal, pulmonary and musculoskeletal conditions may also masquerade as angina.
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1. Presenting symptoms
Classically, stable angina presents with central chest tightness or pain during exertion. The pain settles within 10 minutes of resting, or indeed after the administration of glyceryl trinitrate (GTN) spray.
Angina may also manifest during stress or postprandially. The severity of the pain does not correlate to the extent of coronary disease burden.
Less typical presentations, which are more prevalent in women, include jaw, shoulder, back, arm or epigastric pain, belching or nausea. Breathlessness or exercise-induced palpitations may also occur, perhaps in the absence of chest pain.
Angina may also be asymptomatic, for example in those with neurological damage, such as spinal cord lesions or diabetes mellitus.
The angina questionnaire by Rose and Blackburn, which has been approved by the WHO, has been adopted as a screening tool for angina and predicts morbidity and mortality. It is highly specific but its sensitivity is variable.
2. Acute coronary syndrome
Patients suffering from stable angina are at risk of developing acute coronary syndrome (ACS). It is the role of the cardiologist to determine which angina patients are at risk of ACS and need intervention.
ACS may be classified into unstable angina or MI.
Unstable angina is described as suddenly worsening angina symptoms, prolonged chest pain or angina at rest.
Mortality risk among patients with angina is 0.9-1.4 per cent per year, whereas risk of non-fatal MI varies between 0.5-2.6 per cent per year depending on the data.
Risk of mortality, stroke and ACS is higher in angina patients with severe symptoms, left ventricular systolic dysfunction (LVSD), the elderly and patients with either multiple or severe coronary lesions, particularly affecting the left main stem.
3. Investigations
Basic investigations include FBC, U&Es, glucose, LFTs, TFTs and lipids. Further blood tests may be considered, such as high sensitivity-CRP, N-terminal brain natriuretic peptide and homocysteine, although the value of these is debatable.
A baseline resting ECG should be performed. While this is frequently normal, AF, conduction disturbances or left ventricular hypertrophy may be seen.
4. Stress testing
Stress testing, sometimes referred to as an exercise tolerance test, is used to diagnose angina, and to risk stratify patients with CHD. Adverse prognostic features during the stress test include failure to increase, or a decrease in, systolic BP, exercise-induced arrhythmia and exercise-induced mitral regurgitation.
The stress test is not without risks and MI or even death occurs in around one in 2,500 tests.
In patients who cannot tolerate exercise stress testing, or where stress testing is equivocal, stress imaging may be used. In some patients, pharmacological stressors, such as dobutamine or adenosine, may be used.
5. Imaging
In most centres, conventional, rather than CT or MR, angiography is performed to establish the presence of coronary lesions. Angiography may be performed in patients who have a high risk or equivocal stress test, have severe symptoms, have a failing stent or in those requiring non-cardiac surgery.
It should be remembered that stable plaques are seen on conventional angiography as lesions that partially occlude a coronary artery lumen.
However, unstable plaques (which are more prone to rupture and cause ACS), are often hidden within the vessel wall and hence may be missed by conventional angiography.
These unstable lesions are detected by intracoronary ultrasound, which is not routinely performed in the UK.
6. Management
Patients with unstable angina or symptoms suggestive of MI should be treated as a medical emergency and managed accordingly.
Some protective physiological mechanisms, such as increased ischaemic resistance known as myocardial preconditioning, offer a degree of protection for patients with angina, but ultimately, treatment involves medical and perhaps coronary intervention.
Educate the patient regarding the causes of angina and the importance of adherence to the management strategy.
Advise the patient to seek help if the pain exceeds 10-20 minutes and/or it is not improved by GTN.
The management of risk factors, such as smoking, hypertension, hypercholesterolaemia, diabetes mellitus and obesity are crucial for reducing mortality risk. In addition, treatment of LVSD should be optimised.
A Mediterranean diet and omega-3 rich fatty acids should be encouraged.
All patients should receive an antiplatelet agent, such as aspirin 75-150mg once daily, and GTN spray should be used as required.
Some patients will be aspirin resistant, increasing their risk of adverse coronary events.
Statins have been shown to reduce morbidity and mortality and should be offered to reduce lipid burden.
Post-MI patients or those with LVSD should offered a beta-blocker. Without an alternative indication, beta-blockers may be used for the symptomatic control of angina.
Other drugs used in symptom control include calcium channel blockers, long-acting nitrates and sinus node inhibitors.
There is some data supporting the use of ACE-inhibitors with normal left ventricular function.
Interventional strategies for angina are either percutaneous coronary intervention (PCI) or CABG.
PCI does not confer a survival benefit compared with medical therapy in stable angina but it does offer a better quality of life. Medical therapy may be considered in low-risk groups or in those who do not wish to be physically active.
CABG is indicated in angina patients with left main stem disease, severe disease of the left anterior descending artery, triple vessel disease and multiple lesions in diabetics.
- Dr Thakkar is a GP in Wooburn Green, Buckinghamshire
Resource
European Society of Cardiology. Guidelines on the management of stable angina. 2006.
