What Is a Silent Heart Attack?

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A silent heart attack is a heart attack (myocardial infarction) that occurs without causing noticeable symptoms or, at least, symptoms that people don't recognize as being serious.

Because a silent heart attack—also known as an unrecognized myocardial infarction—doesn't cause notable symptoms, it is often only diagnosed when a person visits the doctor for an unrelated reason. Although "silent," an unrecognized heart attack can be no less deadly than a recognized one, increasing the long-term risk of heart failure by around 35%.

Symptoms

Most people who are having a heart attack know right away that something is wrong. Typically, they experience angina or some other form of severe chest discomfort. Even if the pain is atypical (for instance, affecting the neck and shoulders rather than the chest), the symptoms are usually relentless and impossible to ignore. Other "tell-tale" signs include sudden and profuse cold sweat, rapid heartbeat, and radiating pain up the neck, back, or arm.

By contrast, people who experience a silent heart attack often have no notable symptoms. If there are symptoms, they may be ignored or attributed to some other condition, like heartburn. This is especially true in younger people who don't consider themselves to be candidates for a heart attack.

Commonly missed signs of a silent heart attack include:

  • Shortness of breath
  • Unexplained fatigue or weakness
  • Dizziness
  • Back or jaw pain
  • Nausea or vomiting

Why Some Heart Attacks Are Silent

There are a number of explanations as to why some people have silent heart attacks even when the area of damage is significant or extensive. Among them:

  • Some people simply have higher pain thresholds and do not regard the symptoms as particularly worrisome.
  • Certain medical conditions, especially diabetes and chronic kidney disease, can affect the nerves that carry pain impulses and, as a result, blunt symptoms of angina (chest pain).
  • Cardiac ischemia (characterized by reduced blood flow to the heart) can sometimes produce atypical symptoms, especially in women. Instead of angina, a person may only experience shortness of breath or other non-specific symptoms not readily attributed to the heart.

Causes

It may surprise you to learn that almost half of all heart attacks (roughly 45%) are silent, according to the long-standing Atherosclerosis Risk in Communities (ARIC) Study. People with diabetes appear to be at especially high risk.

Though the risk of a silent heart attack is higher in men than in women (as it is with "classic" heart attacks), the risk of death is higher in women due to the greater likelihood of absent symptoms.

Heart attacks are also more likely to be silent in older people, especially those over 75.

The underlying mechanism of a silent heart attack is no different than that of a classic one. It usually occurs when the buildup of fat (called plaque) in one of the coronary arteries ruptures. The rupture causes a blood clot to form, leading to an acute blockage. Unless the blockage is relieved within a few hours, that section of the heart muscle will die. This is referred to as an ischemic heart attack.

Silent heart attacks are dangerous given that treatment is almost always delayed, increasing the extent of heart muscle damage.

Diagnosis

Because a silent heart attack does not produce notable symptoms, the diagnosis is usually made after the damage has already been done. In some cases, it may be accidentally spotted during an annual physical.

Oftentimes, a doctor will order an electrocardiogram (ECG) if there are chronic symptoms (such as fatigue or shortness of breath) that can't be readily explained by other causes. The ECG can usually detect clear signs of heart damage based on abnormalities in the electrical pattern of a heartbeat.

Thereafter, the diagnosis can be confirmed by performing an echocardiogram, an imaging test that visualizes the heart muscle and coronary arteries using reflected sound waves.

Other forms of diagnostic imaging, such as a nuclear stress test, cardiac magnetic resonance imaging (MRI), or cardiac computerized tomography (CT), will detect which part of the heart muscle is not receiving its normal blood flow.

Treatment

A silent heart attack indicates is that you have significant coronary artery disease (CAD). This is a disease characterized by the buildup of arterial plaque and the development of atherosclerosis (a.k.a. "hardening of the arteries").

Just because you had no overt symptoms should not suggest that your condition is somehow less serious. Neither should it suggest that your response to treatment will be any different than someone with a classic heart attack. In some cases, the opposite may be true given that prompt emergency treatment almost invariably reduces the area of permanent heart muscle damage.

If you have had a silent heart attack, you would receive the same general treatment as any other person who has survived a heart attack. The treatment would be aimed at:

  • Preventing further ischemia with medications and possibly revascularization (with stents or bypass surgery)
  • Preventing the onset of heart failure (when the heart muscle cannot adequately supply blood to the rest of the body)
  • Preventing death from cardiac arrhythmia (abnormal heart rhythms)

Assessing the Need for Additional Treatment

In addition to this standard post-heart attack therapy, people who have had a silent heart attack may need additional treatment based on the results of a cardiac stress test.

The stress test serves two important purposes:

  • Firstly, it allows your doctor to measure the “threshold” of exercise that produces ischemia in you as an individual. This will help direct the appropriate treatment and rehabilitation efforts.
  • Secondly, it helps you recognize the signs of ischemia so that you can respond quickly if a problem occurs. This includes knowing when to take a nitroglycerin tablet when angina occurs.

While stress testing is useful for anyone who has a heart attack, it is particularly important in evaluating people who have experienced a silent heart attack.

Prognosis

You can die from any heart attack, silent or classic. In some cases, the very first sign of CAD may be sudden death. People who have had a silent heart attack may be at risk of this if the damage to the heart is significant and left untreated. For these individuals, a second heart attack could potentially trigger fatal cardiac arrest.

People diagnosed with a silent heart attack tend to have a somewhat worse long-term prognosis than those with a classic heart attack. According to a 2012 study in the journal JAMA, the absolute risk of early death is around 8% higher among those who have had a silent heart attack compared to those who were promptly treated.

The increased risk may be explained in part by the high rate of diabetes among the study participants. All told, around 17% of participants without diabetes had a silent heart attack compared to 21% of those with diabetes.

On its own, diabetes is not only considered an independent risk factor for a silent heart attack but is also associated with an increased risk of mortality for any cardiovascular disease.

Frequently Asked Questions

How long can a silent heart attack last?

Silent heart attacks can last for hours, often with stuttering symptoms (symptoms that come and go). Rather than overt chest pain, there may be generalized discomfort or pressure around the center of the chest—or no chest pain at all.

What happens after a silent heart attack?

As with all heart attacks, the loss of blood flow to the heart muscle can cause scarring and damage. Because a person with a silent heart attack may not realize what has happened, the damage can be extensive and progressively undermine the function of the heart, leading to heart failure.

How are silent heart attacks diagnosed?

A silent heart attack can be initially detected on an electrocardiogram (ECG), which measures the electrical activity during a heartbeat. The diagnosis can then be confirmed with an echocardiogram, an in-office imaging tool that is able to visualize the heart muscle and blood vessels using reflected sound waves.

What are the long-term consequences of a silent heart attack?

Silent heart attacks are associated with a roughly three-fold risk of dying from heart disease and a 34% increased risk of dying from any cause. Silent heart attacks can also increase your risk of a stroke within one month by 47%.

Who is most at risk of a silent heart attack?

There are several conditions that can significantly increase your risk of a silent heart attack, including:

  • Having had a previous heart attack
  • A history of angina
  • Having diabetes
  • Prior coronary bypass surgery, especially in people over 70

A Word From Verywell

CAD, even very significant CAD, does not always produce the typical symptoms described in the textbooks. In fact, heart attacks are fairly common in people who have never had symptoms suggestive of CAD.

If you have several risk factors for CAD, such as smoking, living a sedentary life, being overweight, or having high cholesterol or hypertension, the absence of symptoms should not be taken as proof that everything is fine. Speak with your doctor about ways to reduce your risk which may include medications, changes in diets, exercise, and quitting cigarettes.

It's never too late to start.

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Additional Reading
  • Aldweib N, Negishi K, Hachamovitch R, et al. Impact of Repeat Myocardial Revascularization on Outcome in Patients with Silent Ischemia after Previous Revascularization. J Am Coll Cardiol 2013; 61:1616.
  • Gehi AK, Ali S, Na B, et al. Inducible Ischemia and the Risk of Recurrent Cardiovascular Events in Outpatients with Stable Coronary Heart Disease: the Heart and Soul Study. Arch Intern Med 2008; 168:1423.
  • Gibbons LW, Mitchell TL, Wei M, et al. Maximal Exercise Test as a Predictor of Risk for Mortality from Coronary Heart Disease in Asymptomatic Men. Am J Cardiol 2000; 86:53