What causes a silent heart attack?
On a scientific level, a silent heart attack is identical to any regular heart attack.1 Both are caused when the blood supply to the heart muscle suddenly becomes blocked – usually by a blood clot. However, some people may not experience symptoms for a number of reasons, ranging from genetics to related conditions such as diabetes dulling the sensory nerves.
If, due to your lack of symptoms, you’ve experienced an SMI which has gone undetected, the only way the event will be discovered is if you have a screening, such as an ECG (which measures the electrical activity of your heart), echo ultrasound scan (which looks at your heart and the blood vessels around it), or MRI scan (which produces pictures of the inside of your heart).
"This could happen as part of a routine medical through a private company, or you could be referred for one of these screenings if you later develop a problem such as heart failure, which results from an earlier heart attack in 78% of cases", explains Dr Jerome Ment, a Cardiologist at the Spire Group.2 "In other cases, some patients only learn of a past heart attack when they have a screening in preparation for a completely unrelated procedure such as a hernia repair. Whatever the reason for the screening, and whether it’s an ECG, Echo Ultrasound, or MRI, it will be able to detect scar tissue that has formed as a result of the heart attack, however long ago it may have occurred."
How to identify a silent heart attack
Although there may not be any immediate signs of a silent heart attack in the moment they occur, there are ways of looking back retrospectively to identify any indicating symptoms.
If a heart screening reveals a past SMI, your cardiologist may ask you to cast your mind back and think very carefully about your medical history to identify a time when you may have had other symptoms that you dismissed because they did not seem to relate to your heart. It’s important to remember that not every heart attack involves chest pain – although this is the symptom we all know to look for. Dr Ment explains that, "It is possible to have pain that is just in your back, jaw or arm – and these are not areas you would necessarily associate with your heart."
There have also been reports that those with a high pain threshold are the most likely to have had a silent heart attack – because they do not perceive the pain as being anything they need to take seriously.3 "In these cases, the fact that a patient has not registered the pain as being important does not mean that the heart attack is, in fact, any less serious than one that is accompanied by a lot of pain," says Dr Ment. "Persistent pain at the top of your stomach, or in your jaw, back, or arm, should all ring alarm bells – especially if they’re accompanied by nausea or sweatiness and last for more than 20 minutes. This is a reason to call 999. Many elderly people are far more likely to report feeling faint, breathless or off colour when they have had a heart attack. Pain may not even be the primary feature."
In most cases – whether the heart attack is silent or not – a patient will also experience warning signs in the 24 hours before the event itself. These are usually milder symptoms of the same type that you later associate as having been the heart attack. You could think of them as mini tremors leading up to an earthquake. "They may be due to a partial blockage by a clot or a fatty plaque. Without treatment, the clot can grow and then completely block the artery – producing the classic signs and symptoms of a large heart attack," says Dr Ment. For more information on how to identify the symptoms of heart attacks, see our guide to understanding chest pain.
How to reduce your risk of a silent heart attack
The primary factors that can cause a heart attack, including an SMI, are age and genetics. You are also at greater risk if you are male. According to Dr Ment, "A family history of heart disease doubles your risk of a heart attack." As such, it’s best to try to tackle the risk factors that you can control — namely health and lifestyle factors. "Smoking, eating a lot of fatty fast food, living with untreated type 2 diabetes, high blood pressure and high cholesterol, and taking too little exercise are all factors that you can change. The more you can do to improve your health in these areas, the less your family history and age will put you at risk," says Dr Ment.
Diet for your heart
When it comes to making changes to your diet, Dr Ment recommends a Mediterranean style of eating – with plenty of fresh fruit and vegetables and very little processed food. According to Dr Ment, “Beetroot juice has also been shown to have a positive effect on blood pressure, which can ultimately reduce the risk of experience a heart attack of any type. Integrating this simple change into your diet once a week could potentially have a large impact on preventing the occurrence of an SMI.”
For those who have already experienced an SMI, omega 3 could help to repair the impact on your heart, and prevent any future risk. One Italian study found that regular use of supplements containing omega-3 essential fatty acids may improve scarring of the heart, and stabilise an abnormal heart rhythm following a first heart attack, preventing a subsequent one in future4. Omega 3 can be found in a range of oily fish including salmon, or introduced into your diet through the use of a high-quality supplement. To learn more about the benefits of omega 3 for improving your overall heart health, see our guide to reducing cholesterol with omega 3.
For more information on how to keep your heart healthy, see our heart health hub.
1Zhu-Ming Zhang, Pentti M. Rautaharju, Ronald J. Prineas, Carlos J. Rodriguez, Laura Loehr, Wayne D. Rosamond, Dalane Kitzman, David Couper, and Elsayed Z. Soliman (2016). Race and Sex Differences in the Incidence and Prognostic Significance of Silent Myocardial Infarction in the Atherosclerosis Risk in Communities, AHA Journals
2(2016). National Heart Failure Audit, UCL
3Andrea Milde Ohm, Christopher Sivert Nielsen, Henrik Schirmer, Audun Stubhaug, Tom Wilsgaard, and Haakon LIndekleiv (2016). Pain Tolerance in Persons With Recognized and Unrecognized Myocardial Infarction: A Population-Based, Cross-Sectional Study, Publication
4Temporelli PL, Buda S, Greene SJ (2016). Role of omega-3 polyunsaturated fatty acids after acute coronary syndrome, NCBI