- Stable angina, (aka ‘Angina pectoris’, and colloquially “Angina“) is a syndrome which causes exertion chest pain, received by rest or the use of nitrates
- Stable angina is a clinical syndrome rather than a disease – and represents a clinical manifestation of underlying coronary artery disease
- It occurs when there is insufficient oxygen supply to the heart to meet demand.
- It presents as central or left sided chest pain, with or without radiation to the neck, arm or jaw, and is generally transient, most commonly occurring on exertion, but can also be triggered by emotion
The blood flow to the myocardium is unable to meet demand due to narrowing of the coronary artery, usually by atheroma, and commonly exaggerated by a co-existing spasm of the artery.
- Acute attacks are treated with nitrites (e.g. sublingual GTN spray)
- Long-term management involves the use of beta-blockers, calcium-channel blockers, aspirin and statins
It is extremely important to different this from ACS – acute coronary syndrome (unstable angina, NSTEMI and STEMI) – whereby there is an acute narrowing or complete occlusion of the coronary artery due to blood clot – as the treatment is very different. However, the presenting symptom – chest pain – often feels identical to that of ACS – as the mechanism of the pain is essentially the same – lack of oxygen to the heart muscle.
Differentiating angina and ACS
- If the pain doesn’t resolve within 5 minutes of cessation of activity, and/or with use of GTN spray, treat as ACS
MI causes heart muscle damage, stable angina does not. They have similar symptoms, although the pain of MI is often greater than angina. Any diagnosis of sudden onset chest pain should be treated as ACS until proven otherwise (unless the pain does resolve as above and the patient already has a diagnosis of stable angina)
- Atheroma seen in coronary artery disease – this accounts for the vast majority of cases
- Aortic valve disease
- Hypertrophic cardiomyopathy
Classifying causes by oxygen supply and demand
- Oxygen demand factors – heart rate, blood pressure, left ventricular hypertrophy (more muscle to supply!), valve disease – e.g. aortic stenosis – so the heart has to work hard to pump
- Oxygen supply – duration of diastole (needs to be long enough to allow sufficient blood to flow to the heart), coronary vasomotor tone, haemoglobin levels, oxygen saturation.
People normally experience angina as exertional chest pain that is relieved by rest.
People may also experience myocardial ischaemia as shortness of breath or without symptoms (silent ischaemia)
Other precipitating factors
- Cold weather
- Heavy meals
- Intense emotion
Diagnosing Stable Angina
- This is mainly based on clinical history – and patients will usually present in the Primary care (GP) setting
- Chest Pain – is ‘tight’, heavy’, or ‘gripping’.
- The pain is usually felt behind the sternum and can radiate to the neck, jaw, arms, and sometimes back.
- Shortness of breath (SOB)
- Both pain and SOB brought on by exertion, and relieved by rest
- Symptoms typically last several minutes after the precipitating event has stopped (e.g. exercise or stress)
- Classically relieved by GTN
The likelihood of a diagnosis of angina increases when there are risk factors for cardiovascular disease present:
- ECG – will often be normal – a normal ECG does not exclude a diagnosis of angina or CHD!
- ETT – Exercise tolerance test
- Blood tests – for screening of risk factors – cholesterol, fasting glucose
- Echocardiograph – may be considered to establish the level of left ventricular function
Canadian Cardiovascular Society Angina Classification
This is sometimes used to class the severity of Angina from I-IV. It is very similar to the NYHA classification of Heart Failure
- Class I – ‘Ordinary Activity’ (e.g. walking or climbing stairs) does not precipitate angina
- Class II – Angina precipitated by walking upstairs, cold weather, or meals
- Class III – marked limitation of normal physical activity
- Class IV – Symptoms present at rest, unable to carry out many normal physical activities
The presence of angina indicates underlying coronary artery disease. The next step is to evaluate the severity of this underlying cardiac disease, for the purposes of assessing future risk of myocardial infarction – and in particular whether or not revascularisation (e.g. coronary artery stenting, or coronary artery bypass graft – CABG) is indicated. Prognostic indicators include:
- Left ventricular function
- Stress testing (e.g. treadmill or pharmacological stress test)
- Coronary artery disease extent as seen on angiogram
- Heart failure
Echo gives information about left ventricular function and ventricular and atrial wall motion defects – which are typically secondary to previous myocardial infarction.
- Left-ventricular ejection fraction (LVEF) is a strong predictor of long-term outcome
- LVEF >50% – 12 year survival = 75%
- LVEF 35-49% – 12 year survival = 55%
- LVEF <35% – 12 year survival = 21%
The stress test (aka exercise stress test or exercise tolerance test) is useful for patients with a normal resting ECG, who are physically able to exercise – usually on a treadmill but occasionally available on a bicycle.
- Patients with an abnormal resting ECG – e.g. atrial fibrillation, left ventricular hypertrophy or other ECG changes are more likely to have false positives and may not be appropriate for a stress test
Exercise increases cardiac load and can provoke myocardial ischaemia – which manifests as chest pain, dyspnoea and ECG changes.
Exercise echocardiography is also performed for individuals with difficult to interpret ECGs (e.g. due to pacing or left bundle branch block).
Pharmacological stress testing can be performed in individuals who cannot exercise. In this instance, medication is given to increase cardiac output – placing similar stresses on the heart as exercise.
Coronary Artery Imaging
Usually, this is in the form of angiography. Plain CT scan of the arteries can be performed to assess the level of calcification – but these result correlate poorly to the level of arterial narrowing.
In some lower risk patients, a contrast CT can be performed, but in the majority of cases, and angiogram is the imaging modality of choice.
This gives exact information on the level of narrowing of the coronary arteries, and which vessels are affected. It is particularly useful to help determine if revascularisation is necessary. With medical treatment only (without revascularisation), 12-year survival rates are:
- Single vessel disease – 75%
- Two vessel disease – 59%
- Triple vessel disease – 50%
In particular, proximal narrowing of the left main coronary artery and the left anterior descending artery is associated with a poor prognosis.
Management of stable Angina
This can be divided into lifestyle modifications, pharmacological interventions, and revascularisation.
- Diet advice – plant-based whole foods diet (e.g. mediterranean diet) has been shown to improve long term outcomes
- Alcohol – within safe drinking limits
- Weight – aim for BMI <=25
- Regular exercise – 150 minutes per week of moderate intensity exercise – reduces cardiovascular risk regardless of weight loss, by up to 30%
There are two main mechanisms used to relieve the symptoms of angina:
- Increasing bloodflow to the heart muscle (by dilating coronary arteries) – e.g. wth GTN (Glycerytrinitrate)
- Decreasing the workload on the heart (e.g. with beta-blocker or calcium channel blocker long term)
First line treatment
(either; or of the below)
- Beta-blocker (e.g. atenolol)
- Calcium channel blocker (e.g. verapamil, diltiazem)
Patients will also likely carry GTN spray or pills with them at all times to relieve acute episodes.
Second line treatment
- Long acting nitrate