An Overview of Heart Attack

A heart attack, or myocardial infarction (MI), occurs when an acute blockage of blood flow causes a portion of the heart to die from lack of oxygen, bringing on symptoms such as chest pain, shortness of breath, and inexplicable anxiety—or none at all. In the best-case scenario, a heart attack is a wake-up call—an indication of coronary artery disease (CAD), meaning the heart has been severely damaged. In a less-than-best-case scenario, a heart attack can produce significant disability and premature death. Either way, it's an emergency that requires immediate medical attention followed by treatment ranging from surgery to medication to changes in lifestyle.

Symptoms

A heart attack usually (but not always) produces significant acute symptoms, including:

  • Chest pain that may radiate to the jaw or arm
  • Dyspnea (shortness of breath)
  • Sweating
  • A sense of intense fear or impending doom
  • Sudden nausea or vomiting

Note that many people don’t have these classic symptoms. They may not have chest pain at all—or any pain. They may describe their symptoms as pressure or nondescript discomfort—“a funny feeling.”

In fact, heart attack symptoms may not even be located in the chest but instead show up the back, shoulders, neck, arms, or the pit of the stomach. Some people even dismiss what they're feeling as heartburn.

Sometimes symptoms of a heart attack are so minor those who experience them will brush them off, figuring they'll go away—and often they do. When they finally see a doctor, these are the people who likely will be diagnosed as having had a “silent heart attack.”

Types of Heart Attack

A ruptured plaque can produce several clinical conditions, which together are categorized as acute coronary syndrome (ACS).

In one of these, unstable angina, the blood clot resulting from a plaque rupture is not large enough (or does not last long enough) to produce permanent damage. Although not regarded as a heart attack, without aggressive treatment unstable angina often is followed by one in the near future.

The other ACS conditions are:

  • ST-elevation myocardial infarction (STEMI) in which the blood clot is so extensive and severe a large part of the heart muscle will die without rapid treatment. STEMI is the most severe type of ACS and is so named because it shows up on an electrocardiogram (ECG) as a spike in
  • Non-ST segment elevation myocardial infarction (NSTEMI). In terms of potential severity, NSTEMI ranks between unstable angina and STEMI in that the blockage of the coronary artery is only partial, but still large enough to cause damage to the heart muscle.

Consequences

Beside immediate symptoms, a heart attack can have dire consequences, some right away, others long-term.

Immediate consequences. If the amount of heart muscle affected by a blocked coronary artery is extensive, a person having a heart attack may experience acute heart failure in which he or she experiences shortness of breath, low blood pressure, lightheadedness or syncope, and multi-organ failure. Unless blood flow is restored to the heart rapidly, these physiological repercussions can be fatal.

In addition, during an acute heart attack, the dying muscle can stop beating normally and begin quivering—a heart rhythm disturbance known as ventricular fibrillation (v-fib). Ventricular fibrillation usually can be treated effectively if it occurs when a person is under medical care; if not treated v-fib increases the risk of death within the first few hours of a heart attack.

Long-term consequences. There are three significant ones:

  1. Damage to the heart during a myocardial infarction may leave the organ so weakened that heart failure eventually develops.
  2. Depending on the amount of permanent damage done to the heart, the risk of sudden death may be permanently elevated.
  3. The very fact that a heart attack has occurred places a person at a very high risk of subsequent heart attacks.

Causes

Most heart attacks occur when an atherosclerotic plaque in a coronary artery suddenly ruptures. (A plaque is a clump of cholesterol and other lipids, calcium, and large inflammatory cells called macrophages.)

The plaque rupture triggers the clotting mechanism within the artery, causing a blood clot to form and block blood flow. If the blockage is severe enough, the heart muscle supplied by that artery begins to die and a heart attack occurs.

Researchers aren't certain why plaques rupture. While sometimes they appear to be triggered by, say, intense physical or emotional stress, more often they occur sporadically, for no apparent reason and with no identifiable triggers.

What's more, it isn't 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 ones.

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.

Diagnosis

Diagnosing a heart attack usually isn't difficult when a person is having typical symptoms and says so. Often, however, someone in this situation may they think they're having symptoms related to their heart but will downplay them out of fear—even in a hospital emergency department.

This is understandable but dangerous: The more quickly medical personnel are alerted to the possibility of myocardial infarction, the more quickly they can make (or rule out) that diagnosis.

Every Minute Counts

If you're even the least concerned you're having symptoms originating from your heart, do not hesitate to say so: “I think I’m having a heart attack.”

Besides evaluating obvious symptoms, two tests typically are done to diagnose a heart attack:

  • An electrocardiogram (ECG), a non-invasive test that analyzes the patterns of how the heart beats to reveal abnormal rhythms
  • A blood test to measure cardiac enzymes to detect whether damage to heart cells is occurring)

Treatment

A heart attack is a medical emergency. Muscle tissue is actively dying, so immediate treatment is critical. Minutes can make the difference between complete recovery and permanent disability or death. After that, long-term treatment will be necessary.

Immediate Treatment

Once a person is under medical care and an ongoing myocardial infarction has been diagnosed, doctors typically begin two approaches to treatment typically are begun simultaneously:

Stabilization

The focus is to treat acute symptoms—relieving stress on the heart muscle, normalizing blood pressure, dealing with the ruptured plaque, and stopping blood clots from forming in the damaged artery This is done with medication, typically a combination of nitroglycerin, oxygen, morphine, beta blockers, a statin, aspirin, and another anti-platelet drug such as Plavix.

Revascularization

The goal is to restore blood flow to the dying heart muscle through the blocked coronary artery 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.

With a STEMI, (in which the coronary artery if fully blocked), revascularization is done by using invasive therapy—angioplasty and stenting. If this approach is unfeasible or too risky, thrombolytic therapy—administration of a “clot-busting” drug—is used to dissolve the clot and restore blood flow.

Often an NSTEMI (a partial blockage), can be treated with stabilization measures alone (as can unstable angina). However, most cardiologists believe stenting is more effective for preserving cardiac muscle and often is the preferred approach for both STEMI and NSTEMI. Thrombolytic therapy has been shown to cause more harm than good.

In the majority of cases—especially if treatment is begun quickly—people with acute heart attacks are quite stable within 24 hours. If a person's heart doesn't start again or ​CPR isn't given within four minutes of cardiac arrest, brain damage is almost guaranteed.

Long-Term Treatment

After surviving a heart attack, your doctor will turn to treatment aimed at preventing three potential long-term consequences:

Heart Failure

Muscle damaged in a heart attack is converted into scar tissue. This tissue will hold the heart together but will not help the heart do its job. The chance of heart failure after a heart attack depends in large part on the extent of the damage.

It also depends on how the remaining heart muscle adjusts. Often it will respond by changing its shape, a process called cardiac remodeling. A certain amount of remodeling may be beneficial at first, but chronic remodeling can lead to heart failure.

There are two classes of medications used to prevent remodeling:

Beta blockers, which work by blocking the effect of adrenaline on the heart. Two beta-blocker medications often prescribed after a heart attack are Tenormin (atenolol) and Lopressor (metoprolol).

Angiotensin-converting enzyme (ACE) inhibitors, which affect an enzyme that contributes to the regulation of blood pressure and the amount of sodium in blood. Examples of ACE inhibitors include Capoten (captopril), Vasotec (enalapril), Zestril (lisinopril), Altace (ramipril), and Mavik (trandolarpril).

Sudden Death

The post-heart attack discussion that is often skipped by cardiologists is a 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 those whose hearts have sustained a lot of damage.

Furthermore, the risk of sudden death can be substantially lowered in people whose risk is very high with an implantable defibrillator. Clear guidelines exist regarding which people ought to be considered for an implantable defibrillator after a heart attack. If your doctor doesn't bring up the topics of sudden death or the idea of a defibrillator, ask him or her about both.

Future Heart Attacks

A person who's survived a heart attack has CAD, and so is at an increased risk for another episode of MI. That risk can be substantially improved with medications and by adopting a healthy lifestyle.

In addition to beta blockers and ACE inhibitors, most people who have had a heart attack need to be on statins (cholesterol-lowering drugs), an anticoagulant (blood-clot) medication such as aspirin, and possibly medication to treat or prevent further angina (such as nitrates or calcium channel blockers).

Lifestyle measures that substantially lower future cardiac risk include:

It's a lot to be aware of and think about and really is just the tip of the iceberg. You may want to develop a post-heart attack checklist with the guidance of your doctor to help you both stay on top of the measures you should be taking to stay healthy after your heart attack.

A Word From Verywell

A heart attack is a serious medical event. 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.

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