What Is a Silent Heart Attack?

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

A silent heart attack—also known as an unrecognized myocardial infarction—is often diagnosed only when a person visits a healthcare provider for an unrelated reason. Although "silent," an unrecognized heart attack can be no less damaging 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 example, affecting the neck and shoulders rather than the chest), the symptoms are usually relentless and impossible to ignore. Other telltale signs include sudden and profuse cold sweat, rapid heartbeats, 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. Among them:

  • Some people simply have higher pain thresholds and may not regard the symptoms as particularly worrisome.
  • Certain medical conditions, especially diabetes and chronic kidney disease, can affect the nerves that carry pain signals and, as a result, reduce 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. 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 plaque in a coronary artery spontaneously 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 likelihood of extensive heart muscle damage.

Diagnosis

Because a silent heart attack isn't recognized as it's happening, the diagnosis is usually made after the damage has already been done. Often, a healthcare provider will order an electrocardiogram (ECG) if there are chronic symptoms (such as fatigue or shortness of breath) that can't be explained by other causes. The ECG can usually detect signs of heart damage based on abnormalities in the electrical pattern of a heartbeat.

The diagnosis can often 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), can detect which part of the heart is not receiving its normal blood flow.

Treatment

A silent heart attack is an indication of 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 does it mean that your response to treatment will be any different than someone with a classic heart attack. In fact, the opposite may be true given that prompt emergency treatment almost invariably reduces the area of permanent heart 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 (in which the heart muscle cannot adequately supply blood to the rest of the body)
  • Preventing death from cardiac arrhythmia (abnormal heart rhythms)

Cardiac Stress Testing

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

The stress test serves two important purposes:

  • Firstly, it allows your healthcare provider 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 there is angina.

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, most often caused by cardiac arrest or fatal arrhythmias.

People who have had a silent heart attack may be at greater risk of this if the damage to the heart is significant and has been left untreated. For these individuals, a second heart attack could very well be fatal.

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 people 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 to be an independent risk factor for a silent heart attack but is also associated with an increased risk of mortality from any cardiovascular disease.

Frequently Asked Questions

How long can a silent heart attack last?

Silent heart attacks can last for hours, often with 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 weaken the heart over time, 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 of a beating heart. The diagnosis can then be confirmed with an echocardiogram, an 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 roughly triple the risk of dying from heart disease and increase risk of dying from any cause by 34%. Silent heart attacks can also increase the 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. These include:

  • 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 yourhealthcare provider about ways to reduce your risk, which may include medications, changes in diet, routine exercise, and quitting cigarettes. It's never too late to start.

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