Silent myocardial ischaemia and silent heart attacks: what they are and who is at risk

Ischaemia means that part of the body is not getting enough blood. In the heart, NICE Clinical Knowledge Summaries describe angina as chest pain or constricting discomfort caused by an insufficient blood supply to the heart muscle, usually because of coronary artery disease. The NHS explains that angina happens when the heart does not get enough blood, usually because the vessels supplying it are narrowed or blocked by fatty deposits.

In silent myocardial ischaemia the heart muscle is short of blood but the person does not feel the pain or tightness that normally signals it. The UK pages used for this guide do not give a detailed clinical definition or figures for ischaemia without a heart attack, because the NHS and British Heart Foundation concentrate on the more familiar problem of a silent heart attack. What they do say is clear and important: heart disease does not always announce itself.

The word silent describes the lack of symptoms, not the lack of harm. A heart that is repeatedly short of blood, or that has already been damaged by a heart attack, is at the same risk of future problems whether or not the person felt anything at the time.

The British Heart Foundation defines a silent heart attack as one that has no symptoms. They are often found only weeks, months or years later, for example at a routine check-up, or when ongoing chest pain or breathlessness prompts tests. Some people recall no symptoms at all; others see a doctor for toothache, back pain or generally feeling unwell and are found, after an electrocardiogram (ECG) and blood tests, to have had a silent heart attack.

The charity estimates they make up around a third of all heart attacks. Some people only discover they have had one after having another, which they might have avoided had they been treated the first time.

The NHS notes that heart attack symptoms can also look like indigestion, with a feeling of heaviness in the chest, a stomach ache or heartburn. A heart attack can happen at any time, including at rest. Because the signs are not always dramatic, anyone who thinks they could be having a heart attack should call 999.

The BHF says a silent heart attack can happen to anyone, but is a bit more common in some people. It names elderly people, possibly because they already live with symptoms that may or may not be related to the heart, and people with diabetes, who may not feel chest pain because of nerve damage from their diabetes. The NHS likewise says silent myocardial infarction is more common in older people and people with diabetes.

Underlying risk factors for coronary heart disease still apply. The NHS lists smoking, high blood pressure, high cholesterol, having a close relative who has had a heart attack, diabetes and living with overweight or obesity as factors that make a heart attack more likely. For angina it adds being a man aged 45 or over or a woman aged 55 or over, drinking more than 14 units of alcohol a week and having another condition such as arthritis or kidney disease.

Because there is no pain to prompt a visit, silent ischaemia and silent heart attacks tend to be discovered indirectly: an ECG recorded for another reason, blood tests, an echocardiogram or a scan. The BHF says that when someone sees a doctor for a different problem, investigations such as ECGs and blood tests can show that a heart attack has already happened.

For people with symptoms the NHS describes the usual tests: an ECG, blood tests, an echocardiogram to see whether the heart has been damaged and a coronary angiogram to find where blood flow is blocked. For suspected angina, a GP refers to a cardiologist and tests may include blood tests, ECG, and scans such as an angiogram, MRI or CT.

The BHF advises that if you are at higher risk because of high cholesterol, high blood pressure or diabetes you should talk to your doctor about treatment. Raising the question of heart risk at routine reviews is reasonable even if you feel entirely well.

It is worth being clear about what silent means and does not mean. A person with this problem can still have symptoms at other times. NICE and the NHS describe the typical features of angina and heart attack, and these should be acted on even if previous episodes went unnoticed.

• Call 999 for chest pain that is tight or squeezing, pain spreading to the arms, neck, jaw, back or stomach, severe difficulty breathing, or chest pain with sweating, sickness or light-headedness, as the NHS advises.

• If you have been diagnosed with angina and the pain does not stop after resting or after your medicine, call 999.

• Get help from NHS 111 if angina comes and goes, feels worse than before, happens more often, lasts longer or happens at rest.

• See a GP if you notice new breathlessness, unusual tiredness or other changes that are not normal for you. The NHS says breathlessness is one of the most common symptoms of coronary heart disease.

• Do not drive yourself to A&E. The NHS says the person on the 999 call will advise what to do.

Treatment depends on what tests show. NICE describes management of stable angina as lifestyle advice (stopping smoking, a cardioprotective diet, a healthy weight, more physical activity within symptom limits and sensible alcohol intake), medicines to relieve and prevent symptoms, and secondary prevention. For secondary prevention it says antiplatelet treatment should be considered in all people with stable angina, usually low-dose aspirin, with an ACE inhibitor for those with other specified conditions and treatment for lipids and blood pressure where appropriate.

The NHS adds that medicines can lower the chance of an angina attack, such as beta blockers, and reduce the risk of stroke or heart attack, such as low-dose aspirin or statins, and that some people are advised to have a procedure to increase blood flow, such as coronary angioplasty or bypass surgery.

After a confirmed heart attack, the NHS says people usually receive long-term medicines, including antiplatelets, statins and medicines to lower blood pressure, and are referred to cardiac rehabilitation. For someone whose heart attack was silent, these treatments are just as relevant once the diagnosis is made.

The BHF says the key to preventing a heart attack is a healthy lifestyle. The NHS suggests staying active as symptoms allow, keeping to a healthy weight, eating a balanced diet, not smoking and keeping within 14 units of alcohol a week. If you have angina the NHS says the condition raises the chance of a heart attack or stroke, so treatment and lifestyle changes matter, but that with good control most people can continue with most activities.

Learning that you have had an event you did not notice can be unsettling. The NHS advises speaking to a GP if you feel anxious or low after a heart attack, and the BHF runs information and nurse helplines for people with heart conditions.

On the NHS the route normally begins with a GP or an emergency department, followed by an ECG, blood tests and referral to a cardiologist for echocardiography and, if needed, angiography. Private cardiology clinics also offer ECGs, scans and imaging for people who want faster access, and the tests themselves are the same. Whichever route is used, results should be shared with your GP so that medicines and risk-factor care continue in one place.