An Overview of Heart Attacks

A heart attack (or myocardial infarction) is a very serious condition in which a portion of the heart muscle dies, usually because its blood supply is interrupted. Typically, a heart attack occurs when an atherosclerotic plaque suddenly ruptures in a coronary artery (an artery that supplies blood to the heart muscle), causing an acute blockage in the artery.

A heart attack can have several nasty consequences. It usually (but not always) produces significant acute symptoms, especially chest pain, dyspnea (shortness of breath), or a sense of impending doom. If the heart muscle damage is extensive enough heart failure can develop, either acutely with the heart attack itself, or later on. A heart attack often produces electrical instability in the heart, which can lead to sudden death from ventricular fibrillation.

In the best-case scenario—which is far more likely if you act quickly when you experience the symptoms of a heart attack, and your doctors immediately recognize the problem and rapidly administer the right treatment—a heart attack is a big wake-up call. It indicates that you have a chronic disease (coronary artery disease, or CAD) that has already done at least some damage to your heart and is likely to do more damage unless you take the right steps. In a less-than-best-case scenario, a heart attack can produce significant disability and premature death. Either way, a myocardial infarction is a profound event in anyone’s life.

If you have had a heart attack, or if your risk of having one is elevated, there is a lot you need to know. By understanding the causes, symptoms, preventive measures, and treatment of heart attacks, and by working closely with your doctor, you can optimize your chances of living a long life in good health.

What Causes Heart Attacks?

A closer look at plaque build-up in the arteries that could lead to a heart attack.

Most typically, heart attacks are caused by an acute rupture of a plaque in a coronary artery. The plaque rupture triggers the clotting mechanism within the artery and a blood clot forms. The blood clot blocks the artery to at least some extent. If the acute blockage is severe enough, the heart muscle supplied by that artery begins to die—and a heart attack occurs.

The question of why plaques rupture, and which plaques are most likely to rupture, is an area of active medical research. While sometimes a plaque will rupture after some kind of “triggering” event (such as severe physical or emotional stress), much more often plaque rupture occurs for no apparent reason, quite sporadically, and without any identifiable triggers. Furthermore, it is not at all clear that the larger plaques doctors tend to worry about (the kind identified after a heart catheterization as being “significant blockages”) are more prone to rupture than smaller, much more innocent-looking plaques. The fact is, anyone who has CAD must be regarded as being at risk for a heart attack—whether or not their plaques are labeled as “significant”—and should be treated accordingly.

'Types' of Heart Attacks

A ruptured coronary artery plaque actually can produce at least three different clinical conditions, which are all lumped together under the name acute coronary syndrome, or ACS. Symptoms with all three kinds of ACS tend to be similar, and all three are considered medical emergencies. However, only two of them are considered heart attacks.

The first kind of ACS is called unstable angina. In unstable angina, the blood clot resulting from a plaque rupture is not large enough (or does not last long enough) to produce permanent damage to the heart muscle—so unstable angina is not a heart attack. However, without aggressive treatment unstable angina is often followed in the near future by a heart attack. Read about unstable angina.

The next kind of ACS is called ST-elevation myocardial infarction (STEMI). This name comes from the fact that the “ST segment” portion of the electrocardiogram (ECG) appears elevated in this, the most severe form of ACS. With a STEMI, the blood clot is extensive and severe, so a large part of the heart muscle supplied by the damaged artery will die without rapid treatment. Read about STEMI.

The third kind of ACS is non-ST segment elevation myocardial infarction (NSTEMI), which can be thought of as a condition that is intermediate between unstable angina and STEMI. Here, the blockage of the coronary artery is only partial, but it is still large enough to produce at least some damage to the heart muscle. Read about NSTEMI.

Both STEMI and NSTEMI, without adequate treatment, will produce permanent damage to the heart muscle, so both these types of ACS are considered to be heart attacks. It is important for doctors to distinguish between these two types of heart attacks because the acute treatment can differ between them.

Symptoms of a Heart Attack

The classic symptom of a heart attack is chest pain, that may radiate to the jaw or arm, and that may be accompanied by sweating, and a feeling of intense fear or impending doom.

However, many people with heart attacks don’t have these classic symptoms. They may not have chest pain at all—or any pain. They may describe their symptoms as a pressure, or a nondescript discomfort—“just a funny feeling.” And the symptoms may not localize to the chest, but instead to the back, shoulders, neck, arms, or the pit of the stomach.

People with acute myocardial infarctions may have sudden nausea or vomiting, or shortness of breath. Or, they may simply have what they describe as “heartburn” and nothing else.

All too often, the symptoms of a heart attack are of such a character that they are relatively easy to brush off. It is easy to just wait to see if they go away by themselves. And many times, they do. These people are the ones who will be diagnosed later on, when they finally see a doctor, as having had a so-called “silent heart attack.”

The trouble is that all heart attacks—even the silent ones—produce permanent damage to the heart muscle, often enough damage to cause disability, or shorten life expectancy by a significant amount. To limit the damage, it is critical to recognize that a heart attack may be occurring, and get medical help immediately, while the heart muscle is still salvageable.

Consequences of a Heart Attack

Immediate Consequences. In addition to producing the kinds of symptoms we just talked about, an acute heart attack can cause more severe problems. If the amount of heart muscle affected by the blocked coronary artery is extensive, a person having a heart attack may experience acute heart failure. This heart failure may produce severe shortness of breath, low blood pressure, lightheadedness or syncope, and multi-organ failure. Unless blood flow can be restored to the affected heart muscle very rapidly, this type of acute heart failure often results in death.

In addition, during an acute heart attack the dying heart muscle can become very electrically unstable, and is prone to ventricular fibrillation. So the risk of sudden death within the first few hours of a heart attack is elevated. However, the ventricular fibrillation can usually be treated very effectively (by defibrillation) if it occurs when a person is under medical care. This is yet another reason why it is very important not to try to just “ride out” any symptoms that may represent a heart attack.

Later Consequences. Even after the acute phase of a heart attack is over, there are still several concerns that need to be addressed.

First, the damage done to the heart muscle may leave the heart weakened, and heart failure may eventually develop. Second, depending on the amount of permanent damage done to the heart muscle, the risk of sudden death may be permanently elevated. Thirdly, the very fact that a heart attack has occurred places a person at a very high risk of subsequent heart attacks.

What all this means is that the treatment of a heart attack does not end when the acute event has ended. Ongoing treatment aimed at preventing or mitigating all three of these “late consequence” outcomes is critical.

How Is a Heart Attack Diagnosed?

Diagnosing a heart attack is usually not too difficult—as long as a person’s symptoms alert medical personnel to that possibility. All too often, a person experiencing symptoms they think may be related to their heart will, due to wishful thinking, downplay the symptoms when they arrive in the emergency room. This is the wrong approach. The more quickly the medical personnel are alerted to the possibility of a myocardial infarction, the more quickly they will act to make or rule out that diagnosis.

Remember that, when it comes to a heart attack, every minute counts. So if you are even the least bit concerned that your symptoms may be coming from your heart, you need to say, “I think I’m having a heart attack.” This will get the ball rolling immediately.

In most cases, recording an ECG (which may show changes characteristic of a heart attack) and sending off a blood test to measure cardiac enzymes (which will detect whether damage to heart cells is occurring) will confirm or disprove the diagnosis of heart attack quickly. The sooner the diagnosis is made, the sooner appropriate steps can be taken to stop the damage.

Treatment: The Critical First Hours

An acute heart attack is a medical emergency. Heart muscle is actively dying, and immediate treatment is critical. Minutes can make the difference between complete recovery and permanent disability or death. This is why nobody should ever ignore any disturbing, unexplained symptoms that occur anywhere above the waist.

Once a person is under medical care and an ongoing myocardial infarction has been diagnosed, treatment begins immediately. This acute treatment usually consists of two simultaneous approaches: stabilization and revascularization.

“Stabilization” consists of getting rid of the acute symptoms, relieving stress on the heart muscle, supporting the blood pressure (if necessary), taking steps to stabilize the ruptured plaque, and stopping the formation of blood clots in the damaged artery. This is done by administering nitroglycerin, oxygen, morphine, beta blockers, a statin, aspirin, and another anti-platelet drug such as Plavix.

However, the real key to a good outcome is to revascularize the dying heart muscle—that is, to restore blood flow through the blocked coronary artery—and to do it as quickly as possible. Most permanent cardiac damage can be avoided if the artery can be re-opened within roughly four hours. And at least some permanent damage can be prevented if the artery is opened within eight to 12 hours. Obviously, time is critical.

With a STEMI (the kind of heart attack in which the coronary artery is completely blocked), revascularization is accomplished, preferably, by using invasive therapy—angioplasty and stenting. Sometimes this approach is infeasible or too risky, in which case thrombolytic therapy (a “clot-busting” drug) is used to dissolve the clot and restore blood flow.

With an NSTEMI (the kind of heart attack in which the coronary artery is only partially blocked), thrombolytic therapy has been shown to cause more harm than good, and should be avoided. Sometimes people with an NSTEMI can be treated with stabilization measures alone (which turns out to be the same way unstable angina is treated). However, most cardiologists believe that stenting is more effective in preserving cardiac muscle with NSTEMI, and is often the preferred approach for both STEMI and NSTEMI.

The overall goal during the first few hours is to make sure blood flow is restored to the at-risk heart muscle, to take steps to prevent the immediate re-formation of a blood clot, and to reduce the workload of the overtaxed heart. In the great majority of cases—especially if treatment is begun quickly—people with acute heart attacks are quite stable within 24 hours.

After the First Day: You’ve Survived a Heart Attack—Now What?

Once you have successfully navigated the acute phase of a heart attack—the first 24 hours or so—it is time for you and your doctors to initiate treatment aimed at preventing the three late consequences of a heart attack: heart failure, sudden death, and further heart attacks.

A heart attack kills some of the heart muscle. The dead heart muscle is converted to scar tissue, which holds the heart together but does not contribute to the work of the heart. Whether or not a person develops heart failure after a heart attack depends on the extent of the damage and on how the remaining heart muscle “adjusts” to the new situation. The remaining, normal heart muscle often responds by changing its shape, a process called “remodeling.” While a certain amount of remodeling may be beneficial at first, more chronically, remodeling can lead to heart failure. Read about cardiac remodeling.

There are several things that doctors should do to help their patients’ hearts to avoid cardiac remodeling and help prevent heart failure. Chief among these are the use of beta blockers and ACE inhibitors, but other steps are required as well. You should be aware of all the steps available for preventing heart failure, and make sure your doctor is recommending the ones that apply to you.

The post-heart attack discussion that is most often “skipped” by cardiologists is the discussion about sudden death. This is a topic that many doctors find very hard to talk about. However, sudden death is a substantial risk for many people after a heart attack, especially people who have had a lot of damage to their heart muscle. Furthermore, the risk of sudden death can be substantially lowered, in people whose risk is very high, by the use of an implantable defibrillator. Clear guidelines exist regarding which people ought to be considered for an implantable defibrillator after a heart attack, and your doctor owes you a discussion of whether you may be one of those people.

A person who has survived a heart attack knows something about themselves they might not have known before: They have CAD, and they are at a greatly increased risk for another heart attack. That risk can be substantially improved with medications and adopting a healthy lifestyle. In addition to beta blockers and ACE inhibitors (useful for preventing cardiac remodeling), most people who have had a heart attack need to be on statins and aspirin, and possibly on medication to treat or prevent further angina (such as nitrates or calcium channel blockers).

Lifestyle measures that substantially improve future cardiac risk include ending all tobacco use, eating a heart healthy diet, controlling weight, gaining excellent control of diabetes and hypertension (if you have these), and engaging in regular exercise (preferably beginning with a formal cardiac rehabilitation program).

A Post-Heart Attack Checklist

That’s a whole lot for you to be aware of and to think about. Guess what? It’s also a whole lot for your doctor to be aware of and think about. And in today’s harried medical environment, it is possible that even the most conscientious doctor will miss some of the critical steps necessary to ensure an optimal outcome after a heart attack.

So here’s a post-heart attack checklist that you may find useful. Go over each line of this checklist with your doctor, to make sure neither of you inadvertently neglect a step toward your optimal cardiac health. You’ve been through a lot together—let’s not let either of you allow the ball to be dropped now.

A Word From Verywell

A heart attack is serious business. Fortunately, with what we’ve learned about heart attacks in the last few decades, and with the newer therapies that have been devised to treat them, the chances of dying or having permanent disability after a heart attack have been greatly diminished.

However, in order to receive all the benefits of these remarkable medical advances, you need to know everything you can about heart attacks—in particular, how to recognize that you may be having one, and what you should expect in the way of treatment. We hope this article will get you started with what you need to know.

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