A heart attack, also called a myocardial infarction, or an MI, is death of a part of the heart muscle. This muscle death occurs for the same reason stroke results in brain cell death: lack of blood supply. Heart disease and heart attack have recently surpassed cancer as the leading cause of death in the United States. More than 1.5 million Americans die each year from a heart attack. The good news is that many of these heart attacks are preventable. Heart attack is a dangerous condition in itself, but there are two aspects of it that make it even harder to manage. First of all, heart disease is called the “silent killer” because up to 20% of heart attacks are never noticed by the people that they affect. The muscle damage still occurs though, and their hearts may be drastically weakened. The other problem with heart attack is fully preventable. Currently, nearly half of all heart attack victims wait at least two full hours before seeking expert medical care. What makes this so bad is that the heart is most amenable to healing during those first few hours. Directly after, or even during, a heart attack, blood flow is blocked to the heart muscle. If that blockage is dealt with right away, there may be some heart muscle that was only injured, but didn’t die. In medicine there is a saying “time is muscle,” which emphasizes just how important it is to come into the hospital or call 911 right away if you are feeling chest pain.
The heart is a powerful, hollow muscle with four chambers. The upper chambers are called the atria while the lower chambers are called the ventricles. The two sides of the heart are also divided in half by a large wall, or septum.
To understand the effects of a heart attack, it is important to know the basic structure of the heart. Blood is first-of-all siphoned from the body towards the heart by veins. For the most part, veins carry used, deoxygenated blood back to the heart. It enters the right atrium (remember, the top right chamber), where enough blood is then collected to pump into the bigger right ventricle. The right ventricle is made of a strong enough muscle to squeeze (or pump) this blood towards the lungs on both sides. In the lungs, the blood turns a brighter red as oxygen saturates the cells. This blood then flows back to the heart, but this time enters the left atrium. Again, the heart pauses to collect blood, after which the blood flows into the left ventricle. The left ventricle then pumps this bright, oxygen-rich blood to the entire body, without which, every organ would eventually die.
You may be wondering if there is a difference in the muscle of each part of the heart. The heart’s walls match up exactly to what function they maintain. The atrial walls are thin and floppy since they only need to push blood into a chamber right next to them. The ventricles are much thicker than the atria and the left ventricle is by far thickest of all. This thickness, or bulk, of the muscle is directly related to how strong it is. Think of a bodybuilder compared to a distance runner. The bodybuilder can lift much more weight because his muscles are big. This “big-ness” of these muscles is called hypertrophy. So, if you look at a heart, you will see a large left ventricle with thick walls, a right ventricle with thinner walls and two floppy atria with the thinnest walls of all.
The reason the thickness of the heart’s walls is so important to understand heart attack has to do with blood flow. The left ventricle musculature works hardest in the heart because it alone must supply the entire body with blood. What many people don’t realize, though, is that the heart itself is a muscle that needs its own blood supply. The blood vessels that feed the heart are called the coronary arteries. The coronary arteries that go directly to the left ventricle are larger and go deeper into muscle compared to the vessels feeding the rest of the heart. All of these blood vessels on top of the heart have the same risk of developing atherosclerosis (hardening of the arteries) as those in the rest of the body; however, if a coronary artery to, say, the left ventricle becomes blocked by plaque or a clot, your heart muscle will begin to die. You feel this at first as chest pain or shortness of breath. Eventually, if your heart attack is not treated right away, you will be left with a feeble heart which has trouble pumping blood to the body. In this way a heart attack can affect not only your heart, but your brain, kidneys, and lungs.
Although every heart attack is unique to its victim, they all share a common source: decreased or absent blood flow to the heart muscle. There are three main ways that this can happen. The most common heart attack happens in people with atherosclerosis. Atherosclerosis refers to diseased blood vessels that have plaque buildup in various places of the body. In a thrombotic heart attack, one or more of these waxy, fatty plaques causes a blood clot to form on top of it. Since the plaque had already narrowed the blood vessel, the clot can be enough to completely block it. If this occurs in a blood vessel feeding the heart (a coronary vessel), then the heart will lose blood supply and begin to die. The death of this muscle usually causes the person experiencing it to feel chest pain or pressure, among other symptoms. Even so, there are plenty of heart attacks that occur silently – these may not cause pain, but they definitely weaken the heart muscle.
The second cause of heart attack still involves a blood clot, but this time the blood clot is embolic, or freely floating through the blood stream. When this happens, there is a chance that this clot may lodge itself into one of the narrow coronary blood vessels. Once the clot is lodged, the effect is the same as the description above of a stationary clot lodging itself in the blood vessel. The blood supply to the heart is cut off, and the heart begins to die.
The third cause of heart attack is very rare, but even so, still causes a drop in blood flow to the heart, possibly leading to a heart attack. This third kind is called Prinzmetal angina. This type of heart attack does not involve clots, but instead occurs due to a sudden spasm of the heart’s blood vessels. This spasm cuts off blood supply to the heart, sometimes leading to permanent heart damage or even sudden death. The cause of Prinzmetal angina is unknown, but it may have a genetic component.
The main, most common symptom experienced by someone having a heart attack is chest pain. Most people will describe the pain as a sense of pressure or heaviness in the chest. The pain from a heart attack is almost never sharp. It is a dull throbbing. Heart attack victims also often feel this pain radiating into the left arm, the neck, the jaw, or occasionally the right arm. Some people experience a heart attack as a feeling of severe heartburn, or as nausea or abdominal pain. Victims will often be pale and clammy and perhaps even dizzy. In addition many people feel a “sense of impending doom.”
Women may feel the same symptoms as men if they fall victim to a heart attack, but women are also far more likely than men to experience atypical symptoms of heart attack. For example, women may have a heart attack and feel no chest pain, but instead just feel short of breath, light-headed, or nauseous. Elderly women in particular may only feel these atypical symptoms and not even realize that they are having a heart attack.
Most of the time, initial diagnosis will take place in the emergency room. The doctor will ask you a series of questions about your symptoms and possible risk factors for having heart disease. With this information, it is likely the doctor has already determined that you are suffering a heart attack. Because of this and the seriousness of an untreated heart attack, some treatment may begin to occur before your doctor actually confirms you have had a heart attack. See the Treatment section for more on this.
After the doctor has asked you about your pain and your medical history, he or she will likely set up an electrocardiogram (or ECG) on you, if it wasn’t placed already. The ECG detects the electrical impulses coming from your heart. It does not detect if your heart is actually beating, but if you do have normal electrical activity, it is likely that your heart is beating just fine. The ECG can, however, detect injury to the heart’s muscle cells. These specialized cells conduct an electrical signal that originates in special cells inside the heart. When the heart muscle is damaged, the cells don’t conduct as well, which leads to very specific changes on the ECG. In this way, a doctor may diagnose a heart attack with the evidence from the ECG.
Even though diagnosis of a heart attack may seem easy from the above description, there is more to it than simply determining that you had a heart attack. Once your doctors discover evidence of your heart attack, they will begin treating it, but they will also continue the process of diagnosis to find out how much muscle damage you’ve had as well as what artery is blocked and whether it is possible to remove or dissolve that clot. This may involve certain imaging such as CAT scans or MRIs. You might even have a procedure called an angiogram, which involves dye being injected into your heart arteries (from a long line usually beginning in the pelvis). The doctor will look at where the dye flows well and, more importantly, where the dye might be blocked. If the dye is blocked, it means blood flow is blocked and it is now clear which blood vessel is diseased. This opens the door for a potentially life-saving procedure called “clot-retrieval.” The line already floating in your blood stream may help special doctors to break up the clot and save heart muscle from death. Overall, heart attack diagnosis involves several doctors – first those in the ER, then the cardiologists and last the general physicians who will help you regain function after your heart attack and help you prevent another from happening.
The first treatment you receive during or following a heart attack depends on where you are and how severe your symptoms are. If you feel well enough to drive yourself or be dropped off at the hospital, the first treatment will occur then. If, on the other hand, you or someone else calls 911, you will probably first receive treatment from paramedics. The first, and possibly the most important, aspect of treatment is simple: a baby aspirin. Aspirin is a blood thinner and if you are having a heart attack, it is likely due in some way to a blood clot blocking flow to the heart. Aspirin may help break up the clot as well as keeping future clots from forming. The other things either the paramedics or your ER doctors will give you are oxygen, morphine, and a blood pressure drug called a beta blocker. The oxygen takes some stress away from both your heart and lungs, the morphine decreases pain and anxiety, as well as, decreasing the amount of oxygen the heart needs to survive, and the beta blocker reduces the work that the heart must do to pump blood. All of these treatments are aimed at stabilizing someone having a large heart attack. Treatment may vary slightly depending on how disabling your heart attack is.
After the initial stabilization occurs, there are several avenues of treatment. It is possible that you will have an angiogram to find with artery is blocked and by how much. This procedure can also help treat the heart attack by destroying the clot and restoring blood flow. Another option is to receive a drug that is sometimes called a “clot-buster.” This drug is a powerful blood thinner and has the ability to break up blood clots. It is only safe to give it within 3 hours of your symptoms’ beginning, though. This is one reason why it is so important to get immediate help if you have chest pain or have another reason to believe you are having a heart attack. Another thing for you and those usually around you to remember is that calling 911 is always your best option in the case of a suspected heart attack. Up to 80% of heart attack victims who feel fine except for their chest pain will either drive themselves or get a ride to the hospital. What is dangerous about doing this is that approximately 1 in 300 people die from cardiac arrest on their way to the hospital. If you happen to go into cardiac arrest (no pulse) and you are on an ambulance, the EMTs can administer a “shock” from a machine called the defibrillator. This is the machine you have probably seen on TV and the movies, where paddles are placed on the patient and someone yells, “Clear!” The defibrillator is an extremely important aspect of cardiac care. It is estimated that defibrillation within 3 minutes of the onset of heart attack symptoms (in a person in cardiac arrest) can increase survival from under 5% up to between 30 and 70%.
There is no one single risk factor that causes you to have a high heart attack risk. It is the body working in concert that leads to the development of conditions right for a heart attack to occur. Some of the common risk factors are as follows:
- Age: men over 45 and women over 55 have increased risk
- Gender (after age 60, both sexes share the same risk)
- Diet high in fat and sugar and low in whole grains
- Obesity (especially obesity around your middle; called “apple” obesity)
- High LDL and/or VLD cholesterol and low HDL cholesterol
- High blood pressure
- Sedentary lifestyle: even some activity or exercise prevents against heart attack
- High psychological stress
As you can see, many of these risk factors are correctible. It may be very difficult to stop smoking or lose weight, but it is possible and it is worth the large reduction in heart attack risk you will get! Less painful, perhaps, is simply visiting your doctor regularly and getting tested both for cholesterol levels as well as blood pressure. If you are ok with taking pills, your doctor may prescribe a daily medication for you to lower your cholesterol or blood pressure.